Objective 2. Pathology Support to Reduce Losses to Disease in Spice Crops.


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  1. Pathogen Isolation from Coriander
  2. Evaluation of Foliar Fungicides for Control of Blossom Blight in Coriander and Caraway
  3. Effect of Seed Treatments on the Germination and Establishment of Cumin and other Aromatic Spice Crops
  4. Efficacy and Crop Tolerance Trials for Azoxystrobin for Control of Blossom Blight in Coriander (Coriandrum sativum)

1. Pathogen Isolation from Coriander

Jill Thomson, Department of Plant Sciences, University of Saskatchewan

Although Duczek and others have attempted to identify the organisms responsible for blossom blight of spice crops, there is still some confusion as to which organisms are involved and especially whether the disease may actually represent a complex of organisms that varies with location and prevailing conditions.

In 2005 and 2006 one particular fungus was consistently observed on blighted blossoms of coriander at the University test plots. The fungus was isolated from these blossoms in 2005. Cultures of this fungus were tested for pathogenicity in the greenhouse.

Materials and Methods:

Eight pots of mature coriander plants with some flowers present were inoculated with a spore suspension made from 16 day old culture plates of the unidentified fungus. The suspension contained 1.5 x 10 5 spores/ml plus the surfactant Tween 20.  The spore suspension was misted onto the flowering parts of the plants until water droplets were present. The pots were placed in plastic bags to increase relative humidity.  Four pots were kept covered for 48 hours and four pots were covered for 72 hours. Another four pots were sprayed with distilled water as controls, and two of these were placed in plastic bags for 48 hours to increase humidity.

Results and Discussion:

Typical blossom blight infections developed on plants that were inoculated and bagged for both 48 and 72 hours. Several seed heads from the control plants that were bagged, developed aborted fruit, probably because of higher temperatures developing in the bags, but no spores were produced on these fruits.

Infected florets were collected from inoculated plants five days after inoculation and were incubated at room temperature and high humidity for three days. Spores typical of the isolate were observed in ooze formed on the florets. Photographs were taken of infected florets removed 11 days after inoculation and incubated in a moist chamber at room temperature for two days. The spores were identical to those used in the original inoculation, indicating that the fungus originally isolated from blighted areas was capable of causing blossom blight symptoms on inoculated plants. Blighted flowers were formed on plants bagged for both time periods, indicating a moist period of 72 hours was sufficient for disease development.

The fungus was submitted for identification to the National Fungal Identification Service (NFIS), AAFC, Ottawa. A number of fungi have been implicated in blossom blight of coriander , including AureobasidiumBotrytisFusarium, Alternaria and Sclerotinia. The fungus submitted to Ottawa was identified as aMicrodochium species.  This may be a synonymous with the Aureobasidium species that was originally isolated by Lorne Duzchek. Other Microdochiumspecies, such as M. bolleyi, are known to be synonymous with Aureobasidium species (A. bolleyi, in this case).  However the NFIS wish to confirm this identification with a new isolate, and if possible this will be done in 2008.

It is extremely interesting to note that in 2003, Dennis reported a new disease of coriander associated with a Microdochium species, occurring in southern Australia (Dennis, J.I. 2003. New disease of coriander in Australia associated with a Microdochium species. Plant Pathology 52: 408).  It is possible that the Australian and Canadian diseases may be caused by the same pathogen, particularly if the original coriander seed used in the two countries came from the same location. This matter will be discussed with the author of the Australian paper.

This fungus was not observed on blight infected caraway blossoms isolated from the same field as the coriander. An Ascochyta species is commonly found on infected caraway blossoms, as reported by Lorne Duzchek.


2. Evaluation of Foliar Fungicides for Control of Blossom Blight in Coriander and Caraway

Jill Thomson and Doug Waterer

Summary

Coriander and caraway fields in Saskatchewan are commonly affected by blossom blight resulting in reduced seed yields. Although a single application of the fungicide Quadris (azoxystrobin) is registered for control of blossom blight of coriander, experience in research plots in 2005 and growers’ fields indicate it does not provide adequate control of this disease.  Two applications of the product, at different timings, were evaluated for control of blossom blight of both coriander and caraway in field trials in 2005 and 2006.  Disease levels on coriander were significantly reduced by two applications of Quadris or other fungicides but seed yields were not improved.  Multiple applications of the new fungicide Proline (prothioconazole) provided a high degree of crop protection in the 2007 trial.

Disease levels on caraway were not affected by fungicide applications in 2006 or 2007.  Early application of the fungicide appears to be a critical factor for disease control in caraway.

A fungus associated with blossom blight of coriander in 2005 and 2006 was isolated and was found to cause disease symptoms characteristic of blossom blight when inoculated on plants under greenhouse conditions. The fungus was identified by the National Fungal Identification Service (NFIS), AAFC, Ottawa, as a Microdochium species. A report of a similar fungus occurring on coriander in Australia was made in 2003.

 Background

Coriander (Coriandrum sativum) and caraway (Carum carvi ) represent economically attractive alternative crops in Saskatchewan (Figures 1& 2). The ten-year average acreage of coriander in Saskatchewan is approximately 17,000 acres, with 22,000 acres grown in 2005.  Caraway production in Saskatchewan ranges from 10,000-20,000 acres, with 12,000 acres of biennial caraway grown in the province in 2005.  Production of both these crops can be severely limited by blossom blight, a disease that attacks the crop during flowering, destroying the flowers and thus reducing seed yield (Figures 1, 2, 3 & 4). Initial studies by Dr. Lorne Duczek (formerly of AAFC, Saskatoon) in 2000 to 2002 revealed that a complex of fungal pathogens is responsible for blossom blight of coriander and caraway.  Although the symptoms of blight are similar, the main causal organisms for blossom blight differ for these two spice crops. In coriander the main fungal pathogen associated with blossom blight was identified as an Aureobasidium species, while in caraway the main pathogen was an Ascochyta species. However both these fungal organisms can be found on either crop, and a number of other fungal pathogens were also found on blight infected blossoms –Fusarium avenaceumF. poaeF. culmorumF. equisetiF. sporotrichioidesF. graminearumBotrytis cinereaSclerotinia sclerotiorum, and Alternariaspecies.  In 2002, Dr. Duczek conducted an initial evaluation of the potential to control blossom blight of coriander and caraway by application of the fungicide Quadris (azoxystrobin).  He concluded that although a single application did reduce disease symptoms, this effect was not maintained to the end of the growing season, and seed yield was not increased by the fungicide application.  A single application of Quadris is now registered for control of blossom blight of coriander.

 

Evaluation of fungicides for control of blossom blight of coriander and caraway

Initial trials conducted by L. Duczek indicated that the fungicide azoxystrobin (Quadris) can reduce levels of blossom blight in coriander but the effect of a single application of the fungicide did not continue throughout the season.  Further work by D. Waterer (Dept of Plant Sciences, Saskatoon) in 2004 also concluded that a single application of Quadris did not provide effective control of blossom blight in coriander.

Initial studies on control of blossom blight in caraway in 2004 were not successful as the annual caraway used in the trial did not flower until late in the season, no disease developed and it was not possible to harvest the crop before snowfall.

The possibility of controlling blossom blight of coriander by multiple applications of different fungicide combinations, rates and timing was evaluated in field trials at the University of Saskatchewan in 2005, 2006 and 2007.

A stand of biennial caraway was planted in 2005, and was used for evaluation of the effectiveness of Quadris applications for control of blossom blight of caraway in 2006 and 2007.

Coriander 2005 trial

Materials and Methods:

A large block of coriander was seeded May 28, 2005 at approx 20 lb/acre, using a seed drill, into land at the University of Saskatchewan that was previously planted to coriander in 2004, 2002 and 2001.  This site was chosen because disease was present in the crop in 2004 and thus it was assumed that disease inoculum would be present in 2005. It was necessary to use a site where infection had occurred previously because it would be difficult to simulate natural infection by application of spore suspensions of the complex of pathogens that apparently cause blossom blight. Crop emergence was noted on June 13th and while the plants were still small, 1 x 5m plots were marked out using a rototiller. Seven plots in six replicate blocks were prepared, to accommodate six fungicide application treatments and one control treatment.  The treatments were arranged in a randomized block design.

Overhead irrigation was applied several times during the season, but in general there was sufficient rainfall for crop growth and disease development.

The fungicide treatments used on the coriander crop in 2005 were:
1.Control (no fungicide applied)
2.Quadris (250g/L azoxystrobin,  Syngenta), applied once at early bloom at 280 g ai/ha
3. Quadris applied twice (early bloom and mid-bloom) at 280 g ai/ha
4. Quadris applied three times (early, mid and late bloom) at 90 g ai/ha
5. Headline EC (250g/L pyraclostrobin, BASF) applied at early and late bloom at 100 g ai/ha, plus Bravo 500 (500 g/L chlorothalonil, Syngenta) applied once at 1250 g ai/L at mid bloom.
6. Lance (70% boscalid, BASF) applied at early and late bloom at 300 g ai/L, plus Bravo applied at mid bloom.
7. Dithane (75% mancozeb, Dow AgroSciences) applied at early and late bloom at 1800 g ai/ha, with Bravo applied at mid bloom.

The full rate of Quadris used is slightly higher than the highest rate used in canola for control of Sclerotinia stem rot (250 g ai/ha).  On December 19, 2005, the 280 g ai/ha rate was approved via Minor Use Registration for control of blossom blight of coriander.  All the other chemicals were applied at the manufacturer’s recommended rate except for treatment four, when the standard rate was divided into three applications.

All chemicals were applied in 400 ml water/18m2 , using a hand-held pressurized application system . The chemicals were applied on July 16 (first flowers opening), August 1 (30-40% bloom), August 14 (seed set started), and the plots were rated for disease on 29 July, 12 August, 26 August , 8 September (11 days – 3 weeks after spraying). The disease was rated on 10 plants selected randomly from each plot using the following rating scheme:

0 – no disease
1 – lesions on leaves, not umbels
2 – lesions on stems, not umbels
3 – 1 umbel on plant affected
4 – >1 but <25% umbels affected/plant
5 – 25% to 75% umbels affected/plant
6 – >75% umbels/plant affected
7 – all umbels/plant affected
8 – plant dead from blight infection.

The average score/plot was calculated and the disease scores analyzed for each assessment date. Blossom blight was observed on volunteer coriander plants close to the plots on July 21st and in the plots on July 29th.

The plots were harvested on September using a small plot combine. The seed was cleaned and weighed, and the weight of seed produced per 5 m2 plot was recorded.

 

Results and Discussion:

Very low levels of blossom blight were recorded at the end of July, but by the second assessment on August 12 significantly more disease developed in the control plots. By the end of August the disease was affecting an average of at least one umbel per plant in the plots where fungicide treatments were controlling the disease and between 25 and 50% of the umbels in the untreated plots (Table 1). By the third disease assessment, on September 8th, more than 25% of the umbels showed symptoms of blossom blight in the fungicide treated plots.  In the check treatments more than 75% of the umbels were infected by this stage of the growing season.  There was significantly less disease in September in the plots sprayed with two applications of Quadris, Headline/Bravo, Lance/Bravo and Dithane/Bravo than in the control plots. The single application of Quadris and three applications of a reduced rate of Quadris did not significantly reduce the level of disease when compared with the control.

Despite the high levels of blossom infection, the majority of fungicide treatments did increase the weight of seed produced from the plots (Table 2). Treatments involving two applications of Quadris and the Lance/Bravo treatment more than doubled the plot yield relative to the control. Applications of Headline/Bravo and Dithane/Bravo also significantly increased yield in comparison with the check plots. The least effective treatments were the single application of Quadris and the three applications of Quadris at a low rate.

Table 1.          Effect of fungicide application on blossom blight in coriander on four assessment dates – Saskatoon 2005.

Fungicide treatment

Average disease score on

July 29

August 12

August 26

September 8

Control

.03 a*

1.3 a

5.2 a

6.1 a

Quadris @ full rate X1

0.0 a

0.3 bc

3.6 bc

5.9 ab

Quadris @ full rate X 2

.07 a

0.8 abc

3.5 c

5.7 bc

Quadris @ 1/3 rate X 3

.05 a

0.9 ab

4.4 ab

5.9 ab

Headline X 2, Bravo

.05 a

0.3 bc

3.6 bc

5.5 c

Lance X 2, Bravo

.08 a

0.5 bc

3.2 cd

5.4 c

Dithane, Bravo, Dithane

.05 a

0.2 c

2.6 d

5.5 c

Coefficient of Variance

253.8

79.9

19.2

4.8

* numbers followed by the same letter are not significantly different, using Duncan’s Multiple Range test, P=0.05.

 

Table 2. Effect of fungicide treatment on seed yield of coriander – Saskatoon
 2005.
 

Fungicide treatment

Average seed yield (kg/5m2 )

Control

0.23 c*

Quadris @ full rate X1

0.38 abc

Quadris @ full rate X 2

0.51 a

Quadris @ 1/3 rate X 3

0.33 bc

Headline X 2, Bravo

0.43 ab

Lance X 2, Bravo

0.52 a

Dithane, Bravo, Dithane

0.45 ab

Coefficient of Variance

28.6

* numbers followed by the same letter are not significantly different, using Duncan’s Multiple Range test, P=0.05.

Quadris has recently received registration for control of blossom blight of coriander, based on a single application at the early flowering stage. Data from this trial, as well as trials conducted previously by the University of Saskatchewan, suggest that two applications would be needed to provide any significant degree of crop protection. Using only one application it would be extremely difficult to guarantee that the application was made at the correct time, and that disease would be controlled for a sufficient period to safeguard seed yields. The fact that two applications of Quadris (or Lance + Bravo) resulted in a doubling of yield suggests that this level of treatment might be economically justified.  A single application of Quadris costs $20-$30/acre.  Based on this treatment  increasing yields from 400 to 800lbs/acre, with coriander selling at $ 0.30/ lb, spraying twice would yield an extra $120/acre – more than covering the cost of two fungicide applications.

Three applications of any product combination did not appear to provide any significant increase in disease control or yield relative to two applications – and therefore would not be justified economically.  The third application came late in the season – at full flowering.  Disease that develops later in the season may not impact yield, as late flowers usually do not produce harvestable seed.  The timing of application in relation to crop stage and the arrival of disease inoculum is critical for economic control. Further trials will examine this relationship to determine the most effective spray program.  For example, a pre-bloom application may be worth considering.

Conclusions:

A reduction in blossom blight levels resulting in significant yield improvements was produced when more than one application of foliar-applied fungicide was made to a coriander crop. A single application of fungicide, or multiple applications at a low rate, did not significantly reduce disease levels or increase yield relative to unsprayed control treatments. Two applications of a number of fungicides may well provide an economically sound control option for growers, but further evaluation of the best timing of application in relation to crop growth and disease onset is necessary.

2006 trial

The 2006 trial was conducted at the University of Saskatchewan Horticulture Field Research Station in Saskatoon, on the same plot of land used in the 2005 trial.  This site was chosen because disease was present in the coriander crops in 2004 and 2005 and it was anticipated that disease inoculum levels would be high in 2006. It was necessary to use a site where infection had occurred previously, because it would be difficult to simulate natural infection by application of spore suspensions of the complex of pathogens that cause blossom blight.

A large block of coriander was seeded 1 June 2006, (seed supplied by G. Schweitzer, Eston) at approx 20 lb/acre, using a single cone seed drill. Emergence was noted on June 14th.   Weeds were controlled using a post-emergence application of linuron.  In early July treatment plots (1 x 5 m) were marked out by mowing one meter wide pathways between the plots. Seven treatments with five replicates were arranged in a randomized block design.

There was sufficient rainfall for crop growth and disease development. Irrigation was not applied.

The label rate for Quadris (Syngenta, 250 g /L azoxystrobin) in coriander is 280 g ai/ha.   However, all treatments in this trial used a lower rate (111 g ai/ha) of Quadris – the rate recommended for disease control in pulse crops. This reduced rate was chosen as producers have indicated that it is economically viable to make two applications at this rate.  Previous trials conducted as part of this research project had indicated that multiple fungicide treatments provided superior disease control relative to a single application.  .  The Quadris was applied in the equivalent of 300 L water per hectare. This water volume was higher than would be used commercially but was necessary to ensure adequate coverage using the hand-held pressurized CO2 application type spray system used in this project.

The fungicide treatments used in 2006 were:
1. Quadris (250 g/L azoxystrobin, Syngenta), applied at 111 g ai/ha once at initial bloom
2. Quadris applied at same rate, once at mid bloom
3. Quadris applied at same rate, once at full bloom
4. Quadris applied at same rate, at initial and mid bloom
5. Quadris applied at same rate, at initial and full bloom
6. Quadris applied at same rate, at mid and full bloom
7. Control (no fungicide applied)

The sprays were applied on 25 July when 1% of the plants had flowers petals open (initial bloom), 6 August when 40% of the plants were flowering (mid-bloom) and 10 August when 100% of the plants were flowering and seed set was beginning in the first flowers (full bloom). Disease ratings were conducted on 25 July (before spraying), 4 August, 14 August and 21 August. The disease was rated on 10 plants selected randomly from each plot using the rating scheme described in the preceding section

 

The average score/plot was calculated and the disease scores analyzed for each assessment date.

The plots were harvested on 3 October using a small plot combine. The seed was cleaned and weighed, and the weight of seed produced per 5 m2 plot was recorded.

 

Results and Discussion:

Blossom blight was observed on volunteer coriander plants close to the research plots on 25 July, and was seen in the experimental plots on 4 August.

At the first disease assessment on 4 August only plots sprayed at initial bloom had received an application of fungicide.  None of these plots differed from the control in levels of disease. On August 14 all the spray treatments had been applied and significant treatment effects on disease levels were observed (Table 3). Both the plots sprayed at either initial or mid-bloom with an additional application at full bloom had significantly less disease than most of the other plots.

Table 3.  Effect of timing of application of Quadris on blossom blight in coriander on three assessment dates – Saskatoon 2006.

Fungicide treatment

Average disease score on:

4 August

14 August

21 August

Initial bloom (IB)

0.5 ab*

2.4 a

5.1 a

Mid-bloom (MB)

0.3 b

2.1 a

4.5 ab

Full bloom (FB)

1.2 a

2.7 a

5.0 a

IB and MB

0.9 ab

1.0 bc

4.1 ab

IB and FB

0.1 b

0.6 c

4.3 ab

MB and FB

0.3 b

0.4 c

3.6 b

No fungicide

0.3 b

1.9 ab

4.7 a

Coefficient of Variance (%)

138.4

60.2

19.3

* numbers followed by the same letter in the same column are not significantly different, using Duncan’s Multiple Range test, P=0.1.

At the last assessment the plots receiving two applications of Quadris, at mid and full bloom, still had significantly less disease than the control plots.

None of the fungicide treatments enhanced yields relative to the untreated control.

Conclusions:

Two applications of Quadris were more effective than a single application, particularly when one of the applications was when the crop was at full bloom. This supports the findings of the previous year, when two applications of fungicide controlled disease more effectively than a single application. Unfortunately disease control in 2006 did not result in a yield increase, possibly because of the small plot size. It is also possible that the amount of disease controlled was insufficient to impact on yield in 2006, although disease levels between the two years did not appear to differ.

2007 trial

The trial was conducted at the University of Saskatchewan Horticulture Field Research Station in Saskatoon, on the same site as the two previous trials.  This site had been planted to coriander in five of the past six years and it was anticipated that disease inoculum levels would be high in 2007. It was necessary to use a site where infection had occurred previously, because it would be difficult to simulate natural infection by application of spore suspensions of the complex of pathogens that cause blossom blight.

A large block of coriander was seeded 5 June 2007, (seed supplied by G. Schweitzer, Eston) at approx 20 lb/acre, using a bulk seed drill. Emergence of both volunteer and seeded coriander was noted on June 27th.   Weeds were controlled using a post-emergence application of linuron.  In early July treatment plots (1 x 5 m) were marked out by mowing one meter pathways between the plots. Eight treatments with five replicates were arranged in a randomized block design.

There was sufficient rainfall for crop growth and disease development. Overhead irrigation was applied in the evening in early August to further encourage disease development.

The label rate for Quadris (Syngenta, 250 g /L azoxystrobin) in coriander is 280 g ai/ha.   However, all treatments in the 2006 and 2007 trials used a lower rate (111 g ai/ha) of Quadris – this rate corresponds to the rate used for disease control in pulse crops. This reduced rate was chosen as it would probably be economically viable for producers to make two applications at this rate.   The Quadris was applied in the equivalent of 300 L water per hectare. This water volume was higher than would be used commercially but was necessary to ensure adequate coverage using the hand-held pressurized application system used in this project.  Proline is a new product that controls a wide range of pathogens and is registered for use in canola, cereal and pulse crops.

The fungicide treatments used in 2007 were:
1. Quadris applied once at initial bloom
2. Quadris applied once at mid bloom
3. Quadris applied once at full bloom
4. Quadris applied at initial and mid bloom
5. Quadris applied at initial and full bloom
6. Quadris applied at mid and full bloom
7. Proline (prothioconazole, Bayer CropScience Inc., 480 g/L, applied at 400ml
product/ha). Proline was applied at initial, mid and full bloom.
8. Control (no fungicide applied)

The sprays were applied on 29 July when 1% of the plants had flowers petals open (initial bloom), 4 August when 30-50% of the plants were flowering (mid-bloom) and 14 August when 100% of the plants were flowering and seed set was beginning in the first flowers (full bloom). Disease ratings were conducted on 2 August, 14 August and 27 August. There was no assessment made before the first spray date as almost no disease was observed. Approximately 10% of the plants were infected with aster yellows and some Sclerotinia infections were observed. Blossom blight disease was rated on 10 plants selected randomly from each plot using the rating scheme described for 2005:

The average score/plot was calculated and the disease scores analyzed for each assessment date.

The plots were harvested on 4 October using a small plot combine. The seed was cleaned and weighed, and the weight of seed produced per 5 m2 plot was recorded.

 

Results and Discussion:

Very little blossom blight was observed on either volunteer or seeded coriander plants before the first spray on 29 July. There were no significant differences in the level of disease when the plots were first assessed for disease on August 2. However disease levels had increased by the second assessment date on August 14, 10 days after the second application of fungicides and immediately prior to the third chemical application (Table 3.2.1.4).

There was significantly less disease in the plot that had received 2 applications of Proline, compared with the plots that were either sprayed once with Quadris at early and mid bloom, or not sprayed at all. However, at this date the plots to be sprayed at full bloom had not been sprayed, and the disease levels in these plots were not significantly different from either the plots sprayed earlier with Quadris or the Proline sprayed plots. By the third assessment at the end of August (13 days after the last chemical application) Proline treated plots had significantly less disease than control plots, and so did the plots with one late application of Quadris. It appeared from this trial that the later applications of Quadris were more effective than earlier ones and that Proline was effective when applied three times.

Table 4.  Effect of timing of application of Quadris on blossom blight in coriander on three assessment dates – Saskatoon 2007.

Fungicide treatment

Average disease score on:

2 August

14 August

27 August

Quadris at initial bloom (IB)

0.1

0.7 a*

2.5 ab

Quadris at mid bloom (MB)

0.2

          0.7 a

2.2 ab

Quadris at full bloom (FB)

0.1

0.4 ab

1.9 bc

Quadris at IB and MB

0.1

0.4 ab

2.3 ab

Quadris at IB and FB

0.1

0.4 ab

2.1 b

Quadris at MB and FB

0.1

0.6 ab

2.2 ab

Proline at IB, MB and FB

0.1

0.2 b

1.0 c

No fungicide

0.1

0.7 a

3.1 a

Coefficient of Variance

164.7

66.2

32.7

* numbers followed by the same letter in the same column are not significantly different, using  LSD test, P=0.1.

Timing of fungicide application was obviously important but as it is difficult to be sure of the most effective time to spray.  It was clearly preferable to spray twice to increase the chance of control. Proline obviously has the potential to control blossom blight, but timing was not evaluated in this study. It is important that new chemistries be tested and included in Minor Use registrations as quickly as possible, to ensure producers have effective management options should the pathogens involved develop resistance to the other chemistries.

None of the fungicide treatments enhanced seed yields relative to the untreated control.  This was not surprising as disease scores were generally low, with an average of less than 1 umbel per plant affected.

Conclusions:

In the coriander trial conducted in 2007, three applications of Proline was the most effective treatment in reducing disease. As this treatment would be prohibitively expensive, the optimum timing for one or two applications of this product needs to be examined. Every season is made up of different flowering/ weather interactions and it is extremely difficult to determine a precise recommendation for timing of application of Quadris which is presently registered for the control of blossom blight in coriander.  In 2007 the later applications of Quadris appeared to be more effective, probably as August was wet and conducive to disease development, whereas July was hot and dry and therefore not favorable for the development of blossom blight.

 

Overall conclusions for fungicidal control of blossom blight of coriander:

Two applications of Quadris, or another fungicide, are necessary for control of blossom blight. However this control of disease does not always translate into an increase of yield, in the small plot trial. Timing of the applications is critical in determining efficacy, and this timing may vary depending on crop stage, weather conditions and inoculum level.
It is recommended that the Minor Use label be altered to include two applications of Quadris on coriander.

Caraway 2005 trial

Initial establishment of the biennial caraway was undertaken. A block of caraway similar in size to that of the coriander was planted in the summer 2005.

2006 trial

Materials and Methods:

The large block of biennial caraway (seed supplied by G. Schweitzer, Eston) seeded in the research plots at the University of Saskatchewan in summer 2005 was used for the 2006 trial. In early June of 2006 treatment plots (1 x 5 m) were marked out by mowing one meter pathways between the plots. Seven treatments with five replicates were arranged in a randomized block design. The caraway plants developed rapidly in the spring and were at full bloom by 13 June when the first fungicide application was made. This time of application is later than was initially planned.  Two rates of Quadris were used – a low rate of 111 g ai/ga and a high rate of 222 g ai/ha.  Three treatments received an initial application at 111 g ai/ha and three treatments received an initial application at 222 g ai/ha.  A second application of either the high or low rates was made on four of the treatments on 24 June, when only 10% of the plants were still flowering and the majority of plants were setting seed. The fungicide treatments were:

  1. Quadris applied at high rate at full bloom (H/FB)
  2. Quadris applied at low rate at full bloom  (L/FB)
  3. Quadris applied at high rate at full bloom (H/FB) and late bloom (H/LB)
  4. Quadris applied at low rate at full bloom  (L/FB) and late bloom (L/LB)
  5. Quadris applied at high rate at full bloom (H/FB) and low rate at late bloom (L/LB)
  6. Quadris applied at low rate at full bloom  (L/FB) and high rate at late bloom (H/LB)
  7. Control, no fungicide applied

 

Disease ratings were conducted on 7, 15, 22, 29 June and 6 July.  The disease was rated on 10 plants selected randomly from each plot using the same rating scheme previously described for the coriander. The plots were harvested on 26 July using a small plot combine. The seed was cleaned and weighed, and the weight of seed produced per 5 m2 plot was recorded.

Results and Discussion:

There were no significant differences in disease development between the treated plots on June 7 and June 15, which is not surprising as the first spray application was made on June 13 (Table 5). There were some slight differences between treatments noted on 29 June, but none of the spray applications significantly reduced disease. By the beginning of July, all plots were uniformly infected, with the majority of plants having almost 75% of the umbels showing damage by blossom blight.

Table 5.  Effect of timing and rate of application of Quadris on blossom blight in caraway on five assessment dates – Saskatoon 2006.

Fungicide treatment

Average disease score on:

7 June

15 June

22 June

29 June

6 July

High rate @ full bloom (H/FB)

0.4

2.0

3.3

5.5 ab*

5.6

Low rate @ full bloom (L/FB)

0.8

1.5

3.1

5.1 b

5.6

H/FB + H/LB

0.6

1.4

3.1

5.2 b

5.6

L/FB + L/LB

0.9

1.6

3.8

5.8 a

5.8

H/FB + L/LB

0.8

1.6

2.9

5.2 b

5.6

L/FB + H/LB

0.7

2.0

3.3

5.3 ab

5.6

No fungicide

0.4

1.8

3.6

5.5 ab

5.6

Coefficient of Variance (%)

64.2

35.7

23.1

8.2

6.3

* numbers followed by the same letter in the same column are not significantly different, using Duncan’s Multiple Range test, P=0.1.

Conclusions:

The lack of disease control in this trial is probably due to the late application of fungicides. Typically it is recommended that the first application of fungicides for the control of blossom blight be made by early bloom, and certainly no later than 50% bloom. This trial reinforces the recommendation for early spraying, as late applications did not prevent disease development.

2007 trial

Materials and Methods:

The block of caraway seeded in 2005 and used for the fungicide trial in 2006 was combined in 2006 and allowed to re-grow in 2007. Commercial plantings of caraway are commonly harvested in the second and third year after planting. In early June of 2007 treatment plots (1 x 5 m) were marked out by mowing one meter wide pathways between the plots. Uniform disease development had occurred in the plot in 2006 and disease levels had not been significantly affected by the fungicide treatments tested in 2006. It was therefore assumed that the inoculum over-wintering in the block was uniformly present and that there would not be a carry-over effect from disease control in 2006.  Seven treatments with five replicates were arranged in a randomized block design. The first fungicide application was made on 9 June when plants were already 30% flowering.  The flowering period was short and the third fungicide application was made at seed set, when few blossoms were present.

The fungicide treatments were:

  1. Quadris applied at mid bloom (30-50% plants with first flower open, 9 June)
  2. Quadris applied at late bloom (seed set starting on 50% of plants, 21 June)
  3. Quadris applied at seed set  ( 20% of plants still flowering, remainder set seed, 1 July)
  4. Quadris applied at mid and late bloom
  5. Quadris applied at mid bloom and seed set
  6. Quadris applied at late bloom and seed set
  7. Control, no fungicide applied

Blossoms with suspected blossom blight were sampled on June 28 within the plots, and were incubated under moist conditions at room temperature for 5 days.Ascochyta pycnidia and spores formed on the flower parts, confirming the presence of the blight pathogen.  Infected seed heads were also collected from a separate block of caraway in the same field on July 9 and Ascochyta pycnidia and spores were observed after 24 hours of incubation. This confirms the presence of inoculum in the general plot area.

Plot disease ratings were conducted on 8, 16 and 29 June The disease was rated on 10 plants selected randomly from each plot using the same rating scheme previously described for coriander. The plots were harvested on 8 August using a small plot combine. The seed was cleaned and weighed, and the weight of seed produced per 5 m2 plot was recorded.

Results and Discussion:

Variations in disease level between plots was observed in the first assessment, the day before the first spray application, but there were no significant differences in disease levels between treatments after the plots were sprayed.  The initial spray should have been applied slightly earlier and the following two sprays should have been at weekly intervals. The plants flowered rapidly and the spray window was relatively short.

Disease levels were low in 2007, which was surprising as significant levels of disease had developed in this block of caraway in 2006. It was expected that the disease would carry over in the lower portion of the crop, and that levels of blossom blight would be greater than in the previous year, but this did not occur, despite adequate rainfall.

Fungicide treatments did not have a significant effect on yield.  This is not surprising as there were no observed differences in disease levels.

Conclusions:

Fungicide applications had no effect on disease levels in the caraway plots in 2007. Disease levels were low and the second applications were made later than desirable, when seed was already setting. Fungicides should be applied early in June, when the crop starts flowering.  Disease levels should also be tested at weekly intervals, as the total flowering period of caraway may be as short as three weeks.

Overall conclusions for fungicidal control of blossom blight of caraway:

In the 2006 trial disease development was adequate for testing the efficacy of fungicidal control but the applications were made too late in the flowering period. The spray window is short in caraway and an early application is probably critical, particularly if the crop is to be sprayed twice in the flowering period. Disease levels were unexpectedly low in 2007, and were not adequate for efficacy testing. It was not possible to determine if a single well-timed spray would be effective in caraway. Weather conditions and inoculum levels would likely influence disease development in caraway, just as in coriander.


3. Effect of seed treatments on the germination and establishment of cumin and other aromatic spice crops

Jill Thomson and Doug Waterer

 

Summary

Problems with stand establishment followed by progressive die back of the crop as the season progresses have limited grower interest in cumin (Cuminum cyminum) as a crop in Saskatchewan.  In 2005 cumin stand establishment in the field was improved when seed was treated with the fungicide Apron Maxx (fludioxonil + metalaxyl). The recommended seed treatment, Maxim (fludioxonil), was not effective in this trial. The effect of five seed treatments and one in-furrow treatment on stand establishment of cumin was evaluated in field trials at two research sites and in the greenhouse in 2006. No improvement in seedling establishment due to seed treatment was observed at either field site. Under greenhouse conditions, seed treatments containing metalaxyl (Apron Maxx and L 1269) significantly increased seedling survival in non-sterilized field soils. When field soils were sterilized by autoclaving an excellent stand was achieved irrespective of the seed treatment applied. In a greenhouse trial in 2007 an interaction was observed between soil type, seed treatment efficacy and sterilization of soils. These results indicated that pathogenic fungi may play a significant role in reducing cumin stand establishment in field soil, but there is a complex interaction of other factors that may impact the survival of cumin seedlings under field conditions.

 

Introduction:

The establishment of a cumin crop sufficiently dense to provide a reasonable yield has been problematic for both researchers and producers in Saskatchewan. Poor plant establishment may reflect a number of factors including low seed viability, lack of tolerance of germinating seedlings to spring temperature and moisture conditions and vulnerability of seed and seedlings to attack by soil and seed-borne pathogens. The possibility that seed treatment of cumin may reduce pathogen attack and hence increase plant establishment was examined in field trials and greenhouse experiments in 2005, 2006 and 2007.

Field Trials

2005 trial

The cumin seed used in the field trial was obtained from G. Schweitzer (G.H. Schweitzer Enterprises Ltd, Eston, Saskatchewan). It originated in Turkey and had a germination rate of 86% in petri dishes held at room temperature.  This line has shown reasonable agronomic performance in previous trials and can therefore be considered as “adapted” to Saskatchewan conditions.  The seed was divided into 300 g lots, with each lot receiving a different seed treatment product.  Each seed lot was placed in a plastic tub, the seed treatment was added and the tub was then shaken until the seed was evenly coated with product. All chemicals were added at the recommended rates.  The total volume of liquid applied per 300 g seed lot was made up to 15 ml with water. This is a higher water volume than would be used commercially but it was necessary to ensure equal distribution of the product on the seed.  The treated seed was poured into a plastic tray, dried in a fume hood for 18 hours and stored in a plastic container until seeding 2-4 weeks later. Sufficient seed was treated for use in all field trials and greenhouse experiments.

Seven seed treatments were tested.  An eighth seed lot was treated with water only, this served as a check. The seed treatments were:

  1. L1269 (Bayer CropScience), a.i. 10.8 g/L metalaxyl, 13.5 g/L trifloxystrobin, applied at a rate of 7.4 ml product/kg seed

2.  Allegiance FL (Bayer CropScience), a.i 317 g metalaxyl/L, applied at 0.32 ml           product/kg seed

  1. Gaucho 480 FL (Bayer CropScience), a.i. 480 g/L imidacloprid, applied at 45 ml product/kg seed, plus the fungicide Jazz (at rate in treatment #1).
  2. Gemini (BASF), a.i. 1.25% triticonazole, 12.5% thiram, applied at 3.6 ml product/kg seed
  3. Vitaflo 280 (Bayer CropScience), a.i. 15.59% carbithiin, 13.25% thiram, applied at 3.3 ml product/kg seed
  4. Maxim 480 FS (Syngenta), a.i. 40.3% fludioxonil, applied at 2.6 ml product/25 kg seed
  5. Apron Maxx RTA (Syngenta), a.i. 0.73% fludioxonil, 1.10% metalaxyl-M, applied at 9.6 ml product/kg seed
  6. Control, seed treated with 15 ml water.

Treatment with the insecticide Gaucho was included to determine if insects were reducing seedling viability. A seed coating material, (Precise) and talc was used with the Gaucho application and this treatment was combined with L1269 to provide control of fungal pathogens.

Seed treatments of caraway, coriander and cumin were evaluated at the Horticulture Research plots, University of Saskatchewan, Saskatoon.  Seed treatments of cumin were also evaluated at the Potato Research plots in Saskatoon. A similar cumin trial, using four of the seed treatments was conducted at the AAFC Scott Research Farm.

The Horticulture Field Station site features a Sutherland series clay loam soil (pH 7.4, E.C. <1.0 dS/m).  The test site has been used for the production of various spice crops for the past 4 years.  Problems with stand establishment have been noted in previous trials conducted at this site.  The Horticulture Field Station trials for each of the three spice crops were planted on June 8th, 2005, in individual, randomized blocks with four replicates. Two 1.5m rows of each treatment were planted 25 cm apart, with no pathways between replicates. Seed was planted at 10 mm depth into a moist seed-bed, using a disk seeder designed for planting vegetable seed. Plots received irrigation several times during the season and did not suffer from moisture stress. Plots were hand-weeded when necessary. Heavy rainfall in June and July caused extensive wash-out of the cumin plots at this site.  Seedling establishment data was collected from 3 of the 4 replicates on July 6th.  No further data was collected from the cumin plots at this site as the plant stands suffered severe decline early in the season.

The Potato Research Field site features an Asquith series sandy loam soil (pH 7.6, E.C. 1.1 dS/m).  The field was in long-term forage production until 2002 and then was planted to plough-down crops of canola in 2003 and 2004.  Spice crops have never been grown at this site.

The trial was planted on June 6th, 2005, in a randomized block design with five replicates.
Three meter long rows of each treatment were planted 25 cm apart, with 1 meter pathways between blocks. Seed was planted at 10mm depth into a moist seed-bed, using a disk seeder designed for planting vegetable seed. The trial was located at the edge of the potato plots and received irrigation when the potato plots were irrigated. Plots were hand-weeded several times early in the season.

Emergence counts were made for the first 1m of row on July 12, 29 and August 26. Final stand counts were conducted based on 2m of row in the third week of September. This gave the most accurate count of the number of plants present, as in mid-season it was sometimes difficult to tell how many plants were present if branching occurred below the soil surface.

The trial at the Scott Research Farm was planted on May 19th, directly into wheat stubble. Standard fertilizer and weed control practices were carried out. Treatments were planted in 5m long rows in a randomized block design with four replicates. Plant counts were taken in two randomly chosen 1m sections of row, towards the front and back of each row, on June 16th, August 10th and 31st. This data was used to calculate the average plant count/m2. The crop was combined on August 31st and the average yield (kg/ha) was calculated.

Results and Discussion:

L1269 and Allegiance treatments both increased the initial plant count for cumin at the Horticulture Field Station site.

The data presented are for plants/m, as these were the values taken.  The stand density on a per meter squared basis can be obtained by multiplying the values by four. Thus the average plant stand for cumin was 76 plants/m2.
A continuous stand decline was seen in the cumin plots but  not observed in the other spice crops, suggesting that cumin may be more susceptible to soil pathogens, may have more seed-borne problems, and/or may be less adapted to the growing conditions encountered in Saskatchewan.

Table 1.          Effect of seed treatment on initial stand establishment of caraway, 
coriander and cumin – Horticulture Research Station – July 2005.

Seed treatment

Average plant count (#/m) on July 6 for

Annual caraway

Biennial caraway

Coriander

Cumin

L1269

16.8 a*

77 9 ab

118.2 a

27.5 a

Allegiance FL

20.1 a

109.1 a

83.5 bc

29.7 a

Gaucho 480 FL + L1269

17.1 a

73.7 ab

113.9 ab

21.7 ab

Gemini

21.5 a

69.5 b

96.0 abc

10.0 b

Vitaflo 280

20.1 a

95.5 ab

109.5 ab

18.2 ab

Maxim 480 FS

22.1 a

99.6 ab

114.0 ab

12.2 b

Apron Maxx RTA

18.3 a

67.4 b

106.4 ab

18.8 ab

Control (no chemical)

19.6 a

100.3 ab

71.6 c

13.3 b

Coefficient of variance

21.1

27.0

20.0

32.7

* numbers followed by the same letter are not significantly different, using Duncan’s Multiple Range test, P=0.05.

 

Cumin stand counts at the Potato Research site were highly variable, as shown by the high values for the coefficients of variance (Table 2).  This suggests that more replication or bigger plot sizes are needed when studying problems of this type.  The first cumin plant count taken on July 12, approximately 5 weeks after seeding, showed that there were significantly more plants established per meter of row relative to the non-treated control when the seed was treated with either Apron Maxx or Gaucho + L1269 (Table 2). This result is quite different from the result obtained at the Horticulture site. Soil type and conditions differ at these two sites, and the pathogens present, and their response to the seed treatments is likely to vary.

Table 2.          Effect of seed treatment of cumin plant count at the Potato Research  site – July and August 2005.

Seed Treatment

Plant count per meter of row

July 12

July 29

August 26

L1269

23.8 ab*

20.0 abc

16.0 ab

Allegiance FL

24.2 ab

20.0 abc

15.6 ab

Gaucho 480 FL + L1269

32.2 a

25.0 a

18.4 a

Gemini

15.4 b

12.8 c

9.8 bc

Vitaflo 280

15.2 b

14.0 bc

10.6 abc

Maxim 480 FS

12.6 b

11.8 c

7.0 c

Apron Maxx RTA

33.2 a

22.6 ab

18.4 a

Control (no chemical)

15.8 b

11.4 c

9.6 bc

Coefficient of variance

37.3

37.9

43.8

* values followed by the same letter in the same column are not significantly different using Duncan’s Multiple Range test, P = 0.05.

The seed treated with Maxim, Vitaflo and Gemini did not establish a better initial stand than untreated seed. Although the seed treated with L1269 and Allegiance did show an increase in establishment, this was not significantly greater than the untreated check. At the Horticulture Field Research site the L1269 and Allegiance treatments had increased plant stand. Further evaluation of these treatments is recommended.

The number of cumin plants per meter declined in all treatments as the season progressed.  Dead and dying plants were observed throughout the season.  Root systems of the dying plants were necrotic and lacked side roots, but it was not clear if this damage was a cause or a result of the top die-off. Isolations from the roots of dying cumin plants at other locations showed the presence of Pythium and Fusarium species but the pathogenicity of these isolates was not tested.  Throughout the season the cumin stand counts remained higher in the rows planted with seed treated with Apron Maxx and Gaucho + L1269 (Table 2). On August 19 it was noted that the plants were setting seed and symptoms of blossom blight were also observed in the trial.

The ranking of the treatments remained the same when plant number per 2 metre of row was evaluated in September (Table 3). Seed yields from this trial were extremely poor, with very small, withered, unmarketable seed being produced. The relative yields reflected the final number of plants per row (Table 3).

Table 3.          Effect of seed treatment on the final plant count and seed yield of
cumin at the Potato Research plot site – September 2005.

Seed Treatment

Plant count per 2m of row

Seed yield from 2m of row (g)

L1269

43.6 ab*

26.8 ab

Allegiance FL

42.8 ab

25.7 ab

Gaucho 480 FL + L1269

53.8 a

35.1 a

Gemini

24.4 b

15.4 b

Vitaflo 280

25.0 b

17.6 b

Maxim 480 FS

24.8 b

14.8 b

Apron Maxx RTA

49.8 a

24.3 ab

Control (no chemical)

26.4 b

17.3 b

Coefficient of variance

36.6

38.9

* values followed by the same letter in the same column are not significantly different using Duncan’s Multiple Range test, P= 0.05.

The increased plant establishment obtained when Apron Maxx was applied to the cumin seed indicated that both metalaxyl and fludioxonil may both be important in increasing plant survival. When Maxim, containing fludioxonil alone was applied, plant survival was not increased relative to the control; however, Maxim was applied at half the rate of fludioxonil present in Apron Maxx.  Allegiance, which was applied at a rate of metalaxyl similar to that in Apron Maxx, did not improve plant establishment as significantly as Apron Maxx. Thus it would appear that the combination of metalaxyl and fludioxonil was most effective in increasing stand establishment. L1269 also contained metalaxyl, in combination with trifloxystrobin.  Allegiance and L1269 treatments increased plant establishment, but not as significantly as Apron Maxx and Gaucho + L1269. The presence of the insecticide in Gaucho appeared to increase the plant establishment when compared with the L1269 treatment alone, indicating that insects may influence seedling mortality. This was somewhat unexpected as there was no evidence of insect damage to any of the plants in this trial.  Gaucho is primarily used to control flea beetles and there was no sign of flea beetle damage to the cumin plants. It is possible that wireworms could be causing root damage, making the seedlings more susceptible to subsequent attack by fungal pathogens, but wireworms are not considered to be a problem at this site. Gaucho was applied with a seed conditioner (Precise) and dried with a talc application, all of which could influence the efficacy of this treatment. The effect of Gaucho with and without a fungicide should be evaluated in future trilas. The chemicals present in Gemini and Vitaflo (triticonazole, thiram and carbithiin) did not improve plant establishment when compared with the check.

At the Scott Farm site, Apron Maxx increased plant count at the June evaluation, while the Maxim treatment had fewer plants emerged than in the control (Table 4).

Table 4.          Effect of seed treatments on cumin stand and seed yield at Scott
Research Farm – 2005.

Seed treatment

Average plant count/m2 on

Average yield (kg/ha)

16 June

10 August

31 August

Gemini

110.7 bc*

99.7 a

61.0 a

15.7 a

Vitaflo 280

145.2 b

101.7 a

65.6 a

13.3 a

Maxim 480 FS

102.4 c

70.2 a

45.9 a

10.0 a

Apron Maxx RTA

199.8 a

130.6 a

93.2 a

20.3 a

Control (no chemical)

148.6 b

108.3 a

64.3 a

17.7 a

Coefficient of variance

17.7

47.3

59.8

57.4

* values followed by the same letter in the same column are not significantly different using Duncan’s Multiple Range test, P= 0.05.

Stand count declined in all treatments through the growing season at the Scott site, with an average of 76% of emerged plants surviving by August 10th and only an average of 45% surviving through to harvest.  By August there were no significant effects of any of the seed treatments on plant stand, although the Apron Maxx plots always had the highest counts and the Maxim plots the lowest. Very low plant counts were recorded in one replicate of this trial and only the three “normal” replicates were evaluated after the June count. The decrease in replication and increase in coefficient of variance likely explains the lack of statistical significance of the increased counts and yield data for Apron Maxx in August.  Seed yields reflected the final plant density.  The weight of seed harvested from this trial was less than the amount of seed required to sow this trial.

Conclusions:

Stand establishment and subsequent seedling survival were increased when certain fungicidal seed treatments were applied to cumin seed, indicating that pathogenic fungi were responsible for some of the plant mortality observed in cumin stands. However plants continued to die throughout the growing season and the seed treatments did not prevent this further decline in stand counts. This was not surprising as seed treatments do not generally protect plants from pathogens that continue to attack plants as the growing season progresses.

The product currently registered for use as a seed treatment on spices, Maxim 480 FS (a.i. fludioxonil), applied at the recommended rate did not enhance stand establishment in any of the 2005 trials. Apron Maxx, containing both fludioxonil and metalaxyl, was effective in increasing stand establishment at two of the sites (Potato Research site and initially at Scott), suggesting that both chemicals may be necessary for effective control of the pathogens that are damaging the cumin stand.  Metalaxyl is effective in controlling the pathogenic species Pythium and Phytophthora, and fludioxonil is effective against a range of pathogens including Fusarium and RhizoctoniaPythium and Fusarium species have both been isolated from diseased cumin roots and Rhizoctonia is a common soil-borne pathogen of many crops (including canola, pulses and potato). The increase in cumin stand establishment observed when seed treatments capable of controlling these pathogens are used, suggests that all three pathogenic species may be problematic for the cumin crop. Further testing of seed treatment products at different locations is recommended, as pathogen populations are likely to vary between locations, and seasons.

2006 trial

Materials and Methods:

The cumin seed source used in the 2005 trial was also used in 2006.  The seed was divided into 300 g lots, with each lot receiving a different seed treatment product.  Each seed lot was placed in a plastic tub, the seed treatment was added and the tub was then shaken until the seed was evenly coated with product. All chemicals were added at the recommended rates.  The total volume of liquid applied per 300 g seed lot was made up to 10 ml with water. This is a greater volume than would be used commercially but it was necessary to ensure equal distribution of the product on the seed.  The treated seed was poured into a plastic tray, dried in a fume hood for 18 hours and stored in a plastic container until seeding 1-2 weeks later. Sufficient seed was treated for use in both field and greenhouse trials.

Five seed treatments were tested.  An in-furrow application of Quadris at seeding was also evaluated. One seed lot was not treated, this served as a check. The treatments were:

  1. Apron Maxx RTA (Syngenta), a.i. 0.73% fludioxonil, 1.10% metalaxyl-M,

applied at 9.6 ml product/kg seed

  1. L1269 (Bayer CropScience), a.i. 10.8 g/L metalaxyl, 13.5 g/L trifloxystrobin, applied at a rate of 7.4 ml product/kg seed
  2. Gaucho 480 FL (Bayer CropScience), a.i. 480 g/L imidacloprid, applied at 45 ml product/kg seed
  3. Gaucho 480 FL (Bayer CropScience), a.i. 480 g/L imidacloprid, applied at 45 ml product/kg seed, plus the fungicide L1269 (at rate in treatment #2).
  4. Maxim 480 FS (Syngenta), a.i. 40.3% fludioxonil, applied at 0.21 ml product/ kg seed
  5. Quadris (Syngenta), a.i. 250 g/L azoxystrobin, applied in furrow at 6 ml product in 1500 ml water/100m row
  6. Control, seed treated with 10 ml water.

The treatment that combined the insecticide Gaucho with the fungicide L1269 was effective in 2005, so the insecticide and fungicide were evaluated singly and in combination in 2006. Gaucho was originally included to determine if insects were reducing seedling viability. A seed coating material (Precise) and talc was used with the Gaucho application.

Seed treatments were evaluated at the Potato Research plots, University of Saskatchewan and also at the edge of a barley field at Innovation Place, Saskatoon.   Both sites feature a sandy loam soil.  Neither site had been planted to cumin in the past.  Two 2 m rows of each treatment were planted 30 cm apart, with a 2 m pathway between the 5 replicates, in a randomized block design. The Potato Research Plot trial was planted on May 20 at 10 mm depth into a moist seed-bed, using a disk seeder designed for planting vegetable seed. The seeding rate was 100 seeds per meter. The in-furrow application of Quadris was applied into a 10 cm wide by 5 cm deep furrow using a pressurized sprayer. The furrow was filled in with soil and the cumin was seeded into the treated row.

The Potato Plots received irrigation several times during the season and the cumin did not suffer from moisture stress. Plots were hand-weeded when necessary. The Innovation Place site was planted on May 27 and did not receive irrigation. Weed pressure was high at this site.  Despite hand weeding, the combination of weed competition and moisture stress reduced the vigor of the cumin plants at this site.

Plant counts were made on July 5, 19 and August 4 at the Potato Plot site. Final stand counts were conducted when the plants were removed on September 1. This gave the most accurate stand count, as in mid-season it was sometimes difficult to tell how many plants were present if branching occurred below the soil surface. Plant counts were made on July 18, August 2 and 16 at the Innovation Place site. The numbers were so low and the plants so small by the August 16th count that no further counts were taken.

Results and Discussion:

Field trials:

There were no significant differences between the average plant counts for any of the treatments at all four sampling times (Table 3.3.1.6) at the Potato Plot site. However the Gaucho plus fungicide treatment had the highest score at all times.

It is interesting to note that there was a decrease in plant numbers from early July to mid July, but plant counts remained stable from then on. Even at its peak, the stand was relatively poor (average of 19/m) – considering that the crop was seeded at 100 seeds/m.  When the plants were removed and counted at the beginning of September there appeared to be a slight increase in plant numbers compared with the counts in August. This apparent discrepancy between the counts was probably due to the fact that a cluster of individual plants closely resembled a single robust plant, and was likely counted as such in the August counts. The more accurate count was obtained when the plants were removed and counted.

The stand data from the Potato Research site was highly variable from replicate to replicate, as shown by the high values for the coefficients of variance (Table 5).  Two rows were planted for each treatment, and five replicate blocks were used, in an attempt to manage this variability.

Table 5.  Effect of seed treatments on cumin stands – Potato Research Site, 
2006.

Seed treatment

Average plant count (#/m)

5 July

19 July

4 August

1 September

Apron Maxx RTA

15.0

9.8

10.1

12.1

L1269

16.5

9.9

11.4

11.1

Gaucho 480 FL

20.6

14.3

11.1

16.3

Gaucho 480 FL + L1269

21.0

16.2

17.6

20.2

Maxim 480 FS

19.4

15.5

15.6

16.4

Quadris in- furrow

19.0

13.7

13.1

16.1

Control (no chemical)

20.2

9.4

10.7

11.7

Coefficient of variance (%)

39.6

50.9

49.4

49.0

In 2005 the presence of the insecticide in Gaucho appeared to improve stand establishment when compared with the L1269 treatment alone, indicating that insects may influence seedling mortality. In 2006, the highest plant counts were again obtained with the Gaucho plus fungicide treatment. As mentioned in the introduction, this was somewhat unexpected as there was no evidence of insect damage to any of the plants in this trial.  Flea beetles were observed in the plots and Gaucho is primarily used to control flea beetles.

Yield data were not taken in this trial, as in 2005 seed yields were found to reflect the final plant density. The plant stands were so poor in the 2006 trial that very little seed would have been obtained.

Stand establishment was even more limited at the Innovation Place site than at the Potato Research site – less than 10% of the seeds planted had emerged by July 18 and the stand declined over the remainder of the season (Table 6).  There was no advantage to treating the seed at this site – in fact, the treated seed did not establish as well as the untreated seed. Quadris applied in-furrow was the only treatment that did not reduce plant counts relative to the control.

Table 6. Effect of seed treatments on initial and mid-season stand 
establishment of cumin, Innovation Place Site, 2006

Seed Treatment

Average plant count (#/m) on:

July 18

August 2

August 16

Apron Maxx RTA

6.2 b*

4.7 bc

3.9 bc

L1269

6.1 b

3.9 cd

3.1 cd

Gaucho 480 FL

4.8 b

2.7 d

2.0 d

Gaucho 480 FL + L1269

5.4 b

3.2 cd

2.8 cd

Maxim 480 FS

5.4 b

4.0 cd

3.7 bc

Quadris in- furrow

8.3 a

6.0 ab

5.8 a

Control (no chemical)

9.2 a

6.4 a

5.1 ab

Coefficient of variance (%)

25.7

28.7

34.9

* values within a column followed by the same letter are not significantly different using Duncan’s Multiple Range test, P = 0.1.

Conclusions:

Overall stand counts were low at both sites and crop establishment was very poor. None of the seed treatments increased stand establishment significantly, unlike the findings in 2005. These results demonstrate the importance of testing treatments at different sites, over multiple years.

2007 trial

In trials conducted in 2005 and 2006, there had been only marginal responses to fungicidal seed treatments applied to cumin.  Despite the use of “good” quality seed, stands had been poor from the onset and had further declined over the course of the growing season.  One possible explanation for the poor quality of the initial stand was the use of seeding equipment in 2005 and 2006 that was best suited to small plot trials.   It was decided to utilize larger scale seeding equipment in 2007.

Materials and Methods:

The cumin seed used in the previous trials was used again in 2007. Only one seed treatment, Apron Maxx, was used in an attempt to obtain a reasonable stand.  One kg of seed was treated with Apron Maxx, at 9.6 ml product/kg in 50 ml water. The seed was treated in a plastic bag, shaken to ensure even coating, and allowed to dry for several hours before planting. Seed was planted using a six row seeder. The seed was placed in the two fertilizer boxes, one box with treated seed and the other with untreated seed, so that six rows were planted in one pass, with three rows of treated seed beside three rows of untreated seed. A block of 12 plots, in a three by four design, was planted, with a 6 row X 3m pass made in each plot. The plots were separated by 1m pathways. This trial design was used so that if adequate stand establishment occurred the plots could then be used for a fungicide trial, to evaluate chemical control of blossom blight.  The seed was planted to a depth of 2.5 cm to reach moisture – this may have been deeper than optimal for cumin.

Results and Discussion:

Cumin emergence was noted three weeks after planting. The number of plants/3m, in each of the 6 rows planted per plot, were counted 5 weeks after planting. When the average seedling establishment for the rows was compared there was no significant difference between the untreated and treated seed.

Seedling establishment was generally low and quite variable from replicate to replicate. The plants continued to die during the summer and there were inadequate plant numbers to use in the proposed trial for control of blossom blight.  Until an adequate stand of cumin can be obtained it was not possible to evaluate other diseases in the crop.

Conclusions:

The use of larger seeding equipment did not result in a better stand establishment, and the seed treatment with Apron Maxx did not improve stand establishment at this site.

Overall conclusions for efficacy of seed treatments on cumin stand establishment in the field:

The field trial in 2005 indicated that cumin stand establishment was improved the most when seed was treated with Apron Maxx. The recommended seed treatment, Maxim, was not effective in the 2005 trial. However seed treatments were not effective in the two following years, indicating that poor stand establishment may be caused by a variety of factors that vary between sites, seasons and other conditions. Further work is necessary in order to gain an understanding of the factors affecting stand establishment. Manipulation of these factors may then lead to the establishment of satisfactory stands of cumin.
Greenhouse trials:

2005 trial

Cumin, coriander and caraway plants were grown in the greenhouse in a pathogen-free soil mix to determine if problems in stand establishment were occurring because of pathogens in the soil or on the seed.  If the pathogens were present on the seed then disease would be most severe on plants that had not been treated with a protectant fungicide applied to the seed.

Materials and Methods:

Samples of the seed treatments tested in the 2005 field trials (reported previously) were also evaluated in the greenhouse. Ten 4” pots were planted with 10 seeds from each seed treatment.  The pots were filled with potting soil (Sunshine mix #3).   Although this mix is not sterile, it harbors very few pathogenic organisms.  The pots were arranged in a randomized block design in a greenhouse maintained at 24°C/18°C day/night.  The pots were watered as necessary.  The number of plants emerged per pot was recorded 17 days after planting.  The pots planted with cumin were maintained in the greenhouse for a further 12 weeks to determine if the stand decline observed in field trials also occurred under greenhouse conditions.

Results and Discussion:

The germination percentage for the cumin under the greenhouse conditions used in this trial was far higher than that observed in the field trial (Table 1).  This suggests that;

    • field conditions in the spring were not suited to this crop or,
    • pathogens present in the field soil were killing the seedlings prior to emergence.

 

Table 1. Effect of seed treatment on initial plant count of spices in the greenhouse – July 2005.

Seed treatment

Average germination of 10 seeds 22 days after planting:

Coriander

Annual caraway

Biennial caraway

L1269

8.8 a*

3.0 ab

6.4 ab

Allegiance FL

9.9 a

3.7 a

5.8 ab

Gaucho 480 FL + L1269

8.0 a

3.2 ab

5.2 b

Gemini

8.6 a

2.9 ab

6.9 a

Vitaflo 280

8.1 a

1.9 b

5.6 ab

Maxim 480 FS

8.4 a

3.1 ab

5.8 ab

Apron Maxx RTA

8.3 a

3.0 ab

5.8 ab

Control (no chemical)

9.4 a

2.7 ab

6.7 ab

Coefficient of variance

22.2

53.8

25.3

* values followed by the same letter in the same column are not significantly different using Duncan’s Multiple Range test, P= 0.05.

Germination of coriander was also excellent, while the annual caraway had a low germination %, irrespective of the seed treatment used.

The seed treatments had no effect on germination of coriander planted into “disease-free” soil-less media (Table 1).   As seed treatment effects were observed in the corresponding field trials, this suggests that the cause of some stand establishment problems seen in coriander is pathogens present in the soil. In the annual caraway, the Allegiance treatment increased plant counts in comparison with the Vitaflo treatment, but none of the treatments significantly improved plant counts relative to the untreated control.  A similar result was observed in the biennial caraway and the cumin pots. There were no significant treatment effects for the final plant count for cumin after 12 weeks (Table 2).  It is noteworthy that no decline in plant counts was observed over the 12 weeks that the cumin grew in this trial.  Over 50% of the plants died during a corresponding period of time in the field.  This again suggests that growing conditions in the field and/or pathogens present in the growing environment are killing off the cumin.

 

Table 2. Effect of seed treatment on plant counts for cumin in the greenhouse – 2005.

Seed treatment

Average germination out of 10 seeds

22 days after planting  12 weeks after planting

L1269

8.2 a

8.6 a

Allegiance FL

8.0 a

7.4 a

Gaucho 480 FL + L1269

6.1 b

6.7 a

Gemini

6.7 ab

7.8 a

Vitaflo 280

7.7 a

8.0 a

Maxim 480 FS

7.6 a

7.6 a

Apron Maxx RTA

6.7 ab

7.5 a

Control (no chemical)

7.7 a

8.0 a

Coefficient of variance

20.0

24.4

* values followed by the same letter in the same column are not significantly different using Duncan’s Multiple Range test, P= 0.05.

Conclusions:

The observation that none of the chemical treatments affected plant counts when compared with untreated seed grown in potting soil suggests that any problems seen in the field are likely due to pathogens present in the soil, not on the seed.  These problems would be exacerbated by any stresses caused by unsuitable field conditions (soil moisture and/or temperature).

2006 trial

The 2005 greenhouse trial indicated that the cause of the most of the problems with stand establishment in cumin and coriander was soil-borne pathogens and/or less than ideal abiotic conditions for seed germination.  The 2006 greenhouse trial was designed to further test this hypothesis

Materials and Methods:

The treated seed lots used in the field trials were again evaluated under greenhouse conditions. Ten cumin seeds of each seed treatment were planted in four replicate 4” pots and the germination counted after approximately two weeks and 10 weeks.  Rather than utilizing just soil-less mix as was done in 2005, we opted to also use field soil from the test sites employed in 2006 (Innovation Place and Potato Research sites). The soils were mixed 1:1 with Sunshine Potting mix #4.  Both sterilized and non-sterilized soils were used.  The soils were sterilized by autoclaving for 30 minutes. Pure Sunshine Mix #4 was also tested. The greenhouse tests were started at the end of June, and the last stand counts were taken in September.

Results

When treated seed was planted into non-autoclaved field soil from both sites there were significant fungicide treatment effects on the number of seedlings established after two to four weeks (Table 3).  In both the Potato Site and Innovation Place soil Apron Maxx and L1269 significantly increased seedling number relative to untreated seed. Other treatments in non-sterilized soil were not significantly different from the control and although Gaucho alone had significantly lower seedling number than Gaucho plus L1269 in the potting mix none of the treatments significantly differed from the control. Apron Maxx and L1269 both contain the active ingredient metalaxyl. This chemical is
particularly effective in controlling Phycomycete pathogens such as Pythium and Phytophthora species, suggesting that one of these pathogens may be responsible for the decline in seedling numbers observed in non-sterilized soil.

Table 3. Germination and establishment of treated cumin seed in potting mix,
sterilized and non-sterilized field soil in the greenhouse, 2-4 weeks after planting.

Seed Treatment

Average no. of plants per pot (10 seeds planted):

Potato Field soil

Innovation Place field soil

Sunshine Mix # 4

Non-sterilized

Sterilized

Non-sterilized

Sterilized

Apron Maxx RTA

6.5 a*

5.0

9.8 a

7.3

5.5 ab

L1269

6.5 a

5.5

9.8 a

8.3

4.8 ab

Gaucho 480 FL

3.3 ab

5.0

1.0 c

8.0

3.0 b

Gaucho 480 FL + L1269

4.5 ab

5.0

6.3 b

6.0

6.5 a

Maxim 480 FS

3.0 b

6.0

4.3 bc

6.8

4.8 ab

Control (no chemical)

2.3 b

7.8

3.5 bc

7.8

5.3 ab

Mean

4.4

5.7

5.8

7.4

5.0

Coefficient of variance (%)

48.0

40.3

36.1

31.1

41.9

*values within a column followed by the same letter are not significantly different using Duncan’s Multiple Range test, P = 0.1.

Mean values for the soil types indicated that overall seedling survival was greatest in the Innovation Place soil, and that sterilizing the soil increased seedling survival in both field soils. When the soil was sterilized there was no advantage to using a seed treatment, suggesting that pathogens play a significant role in reducing seedling survival. The extremely poor survival of seedling in the Innovation Place plots, compared with the greenhouse values, implied that factors other than pathogenic attack were playing an important role in reducing the cumin stand in the field – at least early in the growing season.

The numbers of seedlings present in the pots after nine to ten weeks was very similar to the counts after two to four weeks (Table 4). In some cases a few seedlings died and in others late seedlings emerged. In the non-sterile soils, seed treated with Apron Maxx and L1269 still survived significantly better than untreated seed. In the potting soil and sterilized soils there were no significant effects of fungicidal seed treatments, with the exception of a reduction in seedling number for Gaucho plus L1269 compared with the control in sterilized Innovation Place soil.  Treatment with Gaucho alone generally reduced seedling number in all soils, suggesting a phytotoxic effect.

Table 4. Germination and establishment of treated cumin seed in potting mix,
sterilized and non-sterilized field soil in the greenhouse, 9-10 weeks after
planting.

Seed Treatment

Average no. of plants per pot (10 seeds planted):

Potato Field soil

Innovation Place field soil

Sunshine Mix # 4

Non-sterilized

Sterilized

Non-sterilized

Sterilized

Apron Maxx RTA

7.3 a*

6.8

9.3 a

8.3 ab

6.0

L1269

7.5 a

7.3

7.5 ab

9.0 a

6.3

Gaucho 480 FL

3.3 b

6.8

1.0 d

9.3 a

4.0

Gaucho 480 FL + L1269

4.3 b

6.8

6.5 b

5.8 b

6.5

Maxim 480 FS

3.3 b

8.0

3.8 c

6.5 ab

5.5

Control (no chemical)

2.3 b

7.8

3.3 c

8.8 a

6.0

Mean

4.7

7.3

4.7

8.0

5.7

Coefficient of variance (%)

42.7

28.6

26.4

21.1

37.1

* values within a column followed by the same letter are not significantly different using Duncan’s Multiple Range test, P = 0.1.

The mean values again showed that seedling survival after 9-10 weeks was best in sterilized field soil, and was close to the 86% seed germination recorded in sterile petri dishes in the laboratory. Seed planted into Sunshine mix #4 survived better than in the unsterilized field soil but not as well as in the sterilized field soil. This mix does not support seedling survival as well as Sunshine mix #3, which was used in the 2005 tests (average survival of 77% of the seedlings after 3 weeks in the control treatment). Future tests will include autoclaved potting soil mix to determine if this affects seedling survival.

Conclusions:

In 2005 field trials there was a significant advantage to applying seed treatments to cumin seed but in 2006 use of seed treatments did not improve stand establishment under field conditions.  In 2005 seed treated with a mixture of Gaucho and L1269 showed significantly higher seedling survival compared with untreated seed. This effect was seen again in 2006 but the effect was not significant. The variability in the results emphasizes the importance of testing at different sites over a number of years.

Irrespective of seed treatment, the plant stands were very poor in 2006, particularly at the Innovation Place site. This site was not irrigated but soil moisture conditions were adequate throughout June. It is not known if the initial low plant counts were due to non-germination of the seed, or death of seedlings prior to emergence.  These results suggest that applications of seed treatments alone will not solve the establishment problem for the cumin crop.

Seed treatments containing metalaxyl were effective in increasing seedling survival in non-sterilized field soil used in greenhouse experiments. The greenhouse trials were conducted during the summer months when the seed would be germinating and growing at daytime temperatures around 23°C. It is possible that the spring conditions in Saskatchewan are too cold for the seedlings to become established, particularly if there is disease pressure from root rotting pathogens such as Pythium and Phytophthora species.  These pathogens are competent over a wide temperature range.  A later planting of cumin in the field at Scott Research Farm in the summer of 2006 appeared to survive much better than early spring planting  (D. Ulrich, personal communication). Unfortunately cumin is susceptible to frost in the fall so later planting may not allow sufficient time for the crop to mature.

 

Greenhouse trial 2007

In 2007 a similar greenhouse trial was conducted to repeat the evaluation of the effect of seed treatments on seedling establishment reported in 2006. Ten cumin seeds of each seed treatment were planted in four replicate 4” pots and the seedling emergence counted after two and four weeks. In this trial three field soils were used, along with potting soil alone. The soils were from the University Potato Research site (University), from a potato farm in the Allan area (Allan) and from a spice growing farm in the Eston area (Eston). These soils were all a light, sandy type of soil, and cumin had been grown at the University and Eston sites. The soils were mixed 1:1 with Sunshine potting mix #4 (Potting mix), and both sterilized and non-sterilized soils were used.  A sterilized potting mix treatment was included along with a non-sterilized potting mix treatment.  The trial was set up as a factorial design, unlike the previous trial when there were unequal treatments as a sterilized potting soil treatment was not included.

The seed treatments were applied as in the previous trial and were:

1. Apron Maxx RTA (Syngenta), a.i. 0.73% fludioxonil, 1.10% metalaxyl-M,
applied at 9.6 ml product/kg seed

  1. Trilex (formerly L1269, Bayer CropScience), a.i. 10.8g/L metalaxyl, 13.5g/L trifloxystrobin, applied at a rate of 7.4 ml product/kg seed
  2. Maxim 480FS (Syngenta), a.i. 40.3% fludioxonil, applied at 0.21 ml product/ kg seed
  3. Control, seed treated with 10 ml water.

The Gaucho treatments were not included in this trial as the insecticide appeared to have a phytotoxic effect in 2006, which could confound the effect of the fungicide. The trial was started in mid November and terminated at the end of December.

Results and Discussion

In the first seedling count after 2 weeks, there was no effect of seed treatment but there was a significant effect of soil type, and an interaction between soil type and soil sterilization (Table 5). Significantly more seedlings emerged in all the field soils after sterilization, suggesting that pathogens may be responsible for reducing emergence in these soils. Significantly more seedlings emerged in the Allan soil than in the other two field soils. This implies that sterilization of the Allan soil was particularly effective in removing some factor that was causing reduced emergence in this soil. This factor may be a pathogen found specifically in the Allan soil but not at the other two sites. However, the seed treatments had no effect after two weeks, suggesting this factor is not controlled by fungicides. There was no effect of sterilizing the potting soil on seedling emergence, as the non-sterilized potting mix had a very high rate of seed emergence.

Table 5. The effect of soil type and soil sterilization on the establishment of cumin seeds two weeks after planting in the greenhouse.

Soil type

No. of seedlings emerged (out of 10 planted)

Non- Sterilized soil

Sterilized soil

University

  0.95 c*

4.75 b

Allan

1.30 c

6.95 a

Eston

2.20 c

4.70 b

Potting  mix

8.00 a

7.05 a

* values followed by the same letter within the table were not significantly different using the Student’s t test at p<0.05.

After four weeks, seedling emergence had increased overall, from an average of 4.5 to 7.0 seedlings per pot.  Emergence was significantly affected by the soil type and by sterilizing, and there was again an interaction between soil type and sterilization (Table 6).  Again there was no difference between sterilized and non-sterilized potting soil.   After four weeks there was also no difference in seedling establishment between the sterilized field soils and the potting soil.

It also appeared that after four weeks the non-sterilized Eston soil was less detrimental to seed establishment than the other two field soils, although the stand was still significantly lower than in the potting soil mix.

Table 6. The effect of soil type and soil sterilization on establishment of cumin seeds four weeks after planting in the greenhouse.

Soil type

No. of seedlings emerged (out of 10 planted)

Non- Sterilized soil

Sterilized soil

University

  3.85 c*

8.60 a

Allan

3.65 c

8.25 a

Eston

5.60 b

8.90 a

Potting  mix

8.40 a

8.65 a

* values followed by the same letter within the table were not significantly different using the Student’s t test at p<0.05.

After four weeks there was a significant interaction between the seed treatment in the different soils (Table 7) and between the sterilization treatments of the different soils (Table 8), at the 10% probability level.

Table 7. The interaction of soil type and seed treatment on establishment of treated cumin seeds four weeks after planting in the greenhouse.

Soil type No. of seedlings emerged (out of 10) in the different  seed treatments
Apron Maxx Trilex Maxim Control
University 7.40 bc* 6.50 cde 5.80 def 5.20 f
Allan 6.70 cde 6.50 cde 5.00 f 5.60 ef
Eston 6.90 cd 7.20 c 7.40 bc 7.50 bc
Potting mix 8.40 ab 8.40 ab 8.40 ab 8.90 a
                Mean 7.3 7.1 6.7 6.8

* values followed by the same letter within the table were not significantly different using the Student’s t test at p<0.10.

In the University soil, treatment with Apron Maxx and Trilex significantly increased seedling number compared with the untreated seed.  The Apron Maxx treatment was the only treatment where the seedling numbers in the University soil were not significantly lower than in the potting mix.  When seed was treated with Maxim, seedling number in the Eston soil was not significantly different than in the potting mix, but seedling numbers were not significantly higher than for untreated seed.  This indicates that the seed treatments have differing efficacies, depending on the soil type. This is consistent with the interaction observed between seed treatment and soil sterilization (Table 9).

Seedling numbers were consistently higher in sterilized versus non-sterilized soils for all three field soils but there was no effect of sterilizing the potting mix ((Table 8). There were significantly more seedlings produced in the non-sterilized Eston soil compared with the other two non-sterilized field soils, suggesting the Eston soil has fewer or less virulent pathogens present that are controlled by sterilization, as there were no differences in seedling establishment when all the soils were sterilized.

Table 8. The interaction of soil type and soil sterilization on establishment of cumin seeds four weeks after planting in the greenhouse.

Soil type

No. of seedlings emerged (out of 10 planted)

Non- Sterilized soil

Sterilized soil

University

  3.85 c*

8.60 a

Allan

3.65 c

8.25 a

Eston

5.60 b

8.90 a

Potting  mix

8.40 a

8.65 a

* values followed by the same letter within the table were not significantly different using the Student’s t test at p<0.05.

In the non-sterilized soil, treatment with Apron Maxx increased seedling establishment relative to untreated seed and the other two fungicide treatments (Table 9). Apron Maxx has shown efficacy in increasing seedling establishment in previous trials, and would therefore be the seed treatment most likely to be effective in the field. However the efficacy would depend on which pathogens were present in the field soil.  Apron Maxx contains two fungicides that are effective against a broad spectrum of pathogens such as Pythium and Phytophthora species and Fusarium and Rhizoctonia species. In the sterilized soil, treatment with Trilex increased establishment, but the other two fungicides did not affect establishment in comparison with the untreated seed.  Trilex appeared to have some growth promoting activity unrelated to pathogen control as positive responses to this treatment were only seen in the sterilized soil. Trilex was not effective in non-sterilized soil, suggesting that this treatment may not be effective against the pathogens causing seedling blight in cumin in the field.

Table 9. The interaction of seed treatment and soil sterilization on establishment of treated cumin seeds four weeks after planting in the greenhouse.

Seed treatment

No. of seedlings emerged (out of 10 planted)

Non- Sterilized soil

Sterilized soil

Apron Maxx

  6.45 c*

8.25 b

Trilex

5.05 d

9.25 a

Maxim

4.65 d

8.65 ab

Control

5.35 d

8.25 b

* values followed by the same letter within the table were not significantly different using the Student’s t test at p<0.05.

Conclusions:

Seedling emergence and establishment were affected by the type of soil they were grown in, and when the soil was sterilized seedling emergence generally increased. Seed treatments did not affect initial seedling emergence but after four weeks Apron Maxx treatment had an effect in one of the soils. This indicated that different soils contained different pathogens that responded differently to the seed treatments
.
Overall conclusions for efficacy of seed treatments on cumin stand establishment in the greenhouse:

Every soil type is likely to have a specific microflora of pathogens that respond differently to available seed treatments. Thus no single treatment will be effective in all soils. The problem of seedling emergence and stand establishment of cumin is complex and requires more research into understanding the factors responsible for the poor stands observed under Saskatchewan conditions.


4. Efficacy and Crop Tolerance Trials for Azoxystrobin for Control of Blossom Blight in Coriander (Coriandrum sativum)

Corriander blossom blightBlossom blight appears to be a common problem in coriander. The causal organism for blossom blight of coriander appears to vary from region to region. In Saskatchewan, Duczek (2002) isolated a range of potentially pathogenic fungi from affected plants, but identifiedAureobasidium sp. as the primary pathogen in a series of controlled environment trials.

Saskatchewan Agriculture and Food Blossom Blight page

As the name implies, blossom blight typically attacks the flowers, although in severe cases leaves and stems adjacent to heavily infested flowers may also be damaged. Infected flowers fail to set seed resulting in substantial yield loss. The primary inoculum source for blossom blight is likely wind or water borne spores from infected crop residues from the previous season. Establishment and spread of blossom blight is promoted by rain and/or irrigation but in dense canopies dew may be sufficient to allow establishment and localized spread. Commercially available germplasm appears susceptible to blossom blight. Chemical control therefore represents the next line of defence. In preliminary trials conducted by Duczek (2002) and Waterer (2003) a range of foliar applied fungicides appeared to provide at least some protection against blossom blight of coriander and other spice crops. Azoxystrobin (PCP # 256153) applied at first flowering appeared to be one of the more promising products.

This trial is designed to provide crop tolerance and efficacy data in support of minor use registration for azoxystrobin for control of blossom blight in coriander. In addition to the treatments stipulated by the minor use testing program a range of other treatment combinations were evaluated.

 

Materials and Methods

The trial was conducted at the University of Saskatchewan, Horticulture Field Research Center in Saskatoon, SK. This site features a Sutherland series clay soil, (pH 8.0, EC< 1.0 dS, CEC 41 meq/100g, 4.4% organic matter, 65% clay, 25% silt, 10% sand). This site has been used in for varietal development and disease screening on a range of spice crops including coriander for the past three growing seasons. In both 2002 and 2003 blossom blight had been observed in coriander planted at this site.

The plot area was disked and harrowed prior to planting. The registered herbicide Treflan (trifluralin @ 1L ai/a) was applied prior to the field preparation step. No fertilizers were applied as soil tests indicated the plot area had adequate levels of all nutrients (110 kg N/ha, 175 kg P2O5/ha, >1000 kg K2O/ha). Coriander seed (cv. CDC Major) to plant this trial was obtained from Schweitzer’s Seed (Gary Schweitzer) of Eston SK. The supplier had not observed any problems with disease in the year the seed was produced. The plot was seeded on May 5 using a John Deere disk drill. The seed was planted to a depth of 4 cm with 20 cm between drill rows. The seeding rate was relatively high (25 kg/ha), as a complete/thick stand tends to promote development and spread of disease in caraway.

In the last week of June we implemented a supplemental irrigation program in an effort to promote both crop development and the onset of conditions conducive to disease. Each week the plot was irrigated for a minimum of 1 hour (1 cm water applied) utilizing a wheel-move type irrigation system. On June 30, the registered herbicide Afolan F (linuron @ 0.5 L ai/a) was applied to control emerged broadleaf weeds. The herbicide program provided a good level of weed control – and weed competition was not an issue in this trial.

In early July, individual treatment plots were created by tilling out 0.6 m strips in the main plot. Each individual treatment plot measured 10 m * 1.5 m. A randomized complete block design was utilized with four replicates.

 

Fungicide treatments

The treatments tested in this project were:

  • 1. Quadris (Syngenta) at 55, 109 or 280 g ai (azoxystrobin)/ha, single application, applied at early bloom.. This combination of rates and time of application reflects the protocol specified in the minor use testing program.
  • 2. Bravo (Syngenta) applied at 1250 g ai (chlorothalonil)/ha, single application, at early bloom – represents the treated check. This application rate was based on recommendations from the manufacturer for control of similar foliar disease problems in similar stature crops.
  • 3. Quadris applied at 250g ai/ha at two week intervals beginning at bloom
  • 4. Dithane (mancozeb, Rohm & Haas) applied at 1800g ai /ha beginning at bloom and repeated on Aug 17 + Bravo applied at 1250g ai/ha on Aug 1
  • 5. Headline (pyraclostrobin BASF Canada) applied at 100g ai /ha beginning at bloom and again two weeks later + Lance (boscalid, BASF Canada) applied at 300g ai/ha (Aug 17)
  • 6. Lance applied at 300 g a.i./ha at two week intervals beginning at bloom and running through Aug 17.
  • 7. Control – no chemical applied – represents the untreated check.

The spray program was initiated on July 26th at which time the crop was just beginning to come into bloom. The sprays were applied using a CO2 powered backback sprayer (276 kPa) utilizing cone-type nozzles. The fungicides were applied in the equivalent of 200 l water/ha.

 

Disease Evaluation

The first disease rating was conducted on August 6th , 11 days after the fungicide treatments were applied and 7 days after symptoms of disease were first observed. Disease incidence was assessed by examining 10 randomly chosen locations per plot for presence/absence (+/-) of blossom blight. The number of infected areas per plot was evaluated again on Aug 19 and 26. The final disease assessment was conducted on September 9. At that time, the % of each plot affected by blossom blight was evaluated.

 

Harvest

Each plot was individually harvested by direct combining on October 7. Recovery of the coriander fruit (seeds + associated ovary elements) was excellent. The fruit were dried at 30oC for 48 hours and then were run through a dockage tester (Carter and Day – Model # XT3) to remove debris and to segregate out the fruit that had failed to set seed. Yield of both empty and full fruit balls was determined for each plot. The 1000 seed (fruit) weight was determined for each treatment replicate.

 

Results

Weather Conditions and Crop Observation

Below normal temperatures delayed emergence of the coriander crop until the 2nd week of June (5 weeks after seeding). The cool conditions also resulted in a staggered emergence pattern – with plants continuing to emerge through early July. This resulted in non-uniformity of crop staging for the duration of the growing season. Replicates 2 and 4 were clearly more developmentally advanced than the other replicates. This contributed to the significant block effects seen in all statistical analyses.

By late June weather conditions were more favorable and the crop showed decent vegetative growth. However, the remainder of the 2004 cropping season was abnormally cool and cloudy and crop development was slow. The crop had begun to bolt by the 2nd week of July, with the first flowers opening a week later. By the 2nd week of August, the coriander plot was in full bloom and because of the cool, moist conditions it continued to bloom until early September. On August 19th the plots were hit by a light frost (-2C) but no crop damage was observed. A killing frost occurred in the last week of September.

No insect pests were observed. Sclerotinia and aster yellow diseases were observed at low levels late in the season – but these diseases were of limited severity relative to the blossom blight. There was some lodging, but this did not interfere with crop recovery at harvest.

Weather conditions at the time of spraying (July 26th – 7 am ) were calm and 15C. At 12:30 pm that day a brief rain shower occurred. There were also light showers on the 27th and 28th … but the total accumulated moisture was minimal (0.10 cm) and should have not compromised product efficacy.

 

Disease Development

The first signs of blossom blight were observed on July 29, with plants in one area of the plot showing the characteristics symptoms of browning of the developing flowers and associated leaves. This affected area slowly increased in size, eventually covering ca. 10 m2. Additional diseased areas appeared in the plots daily and these disease zones also increased in size.

August 6 – the disease was just getting established in the plots at this time. Disease distribution was non-uniform both within blocks and across treatments. There were no significant differences between disease incidence in the controls versus any of the spray treatments at this time.

August 19 – disease levels had increased relative to the previous sampling date, but the disease distribution continued to be non-uniform across both treatments and blocks. There were no significant differences between disease incidence in the controls versus any of the spray treatments at this time.

August 26 – averaged over the entire trial area, disease was found in over 75% of all sites examined. There were no significant differences between disease incidence in the controls versus any of the spray treatments at this time.

September 9 – the plots were rated as to the % of the total plot showing browning and blighting of flowers – no differences were observed between any of the fungicide treatments and the control. On average 36% of the plot area was affected by disease at this time.

Table 2.1. Means and analyses of variance for fungicide effects on coriander disease ratings at various points in the growing season.

Treatment Average number of infected spots
(out of 10)
% plot area infected
August 6 August 19 August 26 September 9
Quadris

55 g ai/ha

0.5 2 7 40

109 g ai/ha

0.25 1 8.2 35

280 g ai/ha

0.25 1.25 8 32
Bravo (1 applic) 0 0.25 7.8 40
Quadris (3 applic) 0.25 1.75 6.8 35
Dithane/Bravo/Dithane 0 2 7 29
Headline/Headline/Lance 23 0 5.5 29
Lance (3 applic) 0 1 8.8 22
Control 0 1.8 0.2 32
P values for Treatment 0.44 0.32 0.66 0.9

 

Yields

There were no significant treatment effects for any of the yield parameters measured. Block to block variability in yields was high … in part due to uneven crop development and in part due to the uneven distribution of disease within the plots. Many of the fruit balls failed to form seed, particularly in areas hardest hit by the blossom blight. Dockage rates exceeded 40% for all treatments.

There were no indications (visual or yields) of any of the fungicide treatments exerting phytotoxic effects on the crop.

 

Conclusion

None of the fungicide treatments tested resulted in disease levels that differed significantly from untreated check areas. Coriander is an indeterminate type plant with an extended bloom period. Based on the results form this single year of testing, it does not appear that a single application of a protectant type fungicide such as Quadris has much potential to protect the crop from blossom blight. Although multiple applications would likely be required – none of the treatment combinations tested in 2004 provided a significant degree of control of ths disease problem.

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