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Vegetable Report: August 10-16, 2013

The crops are growing well and the incidence of aster yellows is very minor. The Aster leafhopper numbers trapped continue to be low this week also.
Insect Net Sweeps ALH On Yellow Cards (3x5")
ALH per 100 sweeps
Aug 13
Trapped in 1 week
(Aug 7-13)
ALH per Sq Inch in 1 week
(Aug 7-13)
Grower 1, Field 1 0 1 0.1
Grower 1, Field 2 6 16 1.1
Grower 2, Field 1 0 1 0.1
Grower 2, Field 2 2 3 0.2
Grower 2, Field 3 2 3 0.2
Grower 3, Field 1 1
Grower 3, Field 2 4
To date (Aug 16) no late blight has been found in Manitoba on tomatoes or potatoes. If you see symptoms resembling late blight, please contact us and we can arrange for confirmation of the disease.
Early blight is showing up in some early maturing varieties. The disease is favoured by warm and moist conditions within the canopy. Disease most often appears first on the lower and older leaves.

Tomato with Early Blight
Edible beans:
Due to frequent rains in the last few days, the micro-climate within the heavily grown crop of edible beans is showing infection by Sclerotinia (white mould). Good air movement through wide spacing is the solution but this needs to be done during planting. Chemical options are also helpful. It is important to keep in mind the pre-harvest interval before applying the products.
Product Preharvest Interval (PHI)
Boscalid-Lance 21 days
Fluazinam - Allegro 30 days
Iprodione - Rovral WDG Apply at 25 - 75% bloom
Thiophanate-methyl - Senator 70 WP 14 days
Dicloran - Botran 75 WP 2 days
Coniothyrium minitans - Contans WG 0 days  Bio-control fungal spore suspension must be applied 3 months prior to anticipated disease occurrence
Bacillus subtilis - Serenade ASO 0 days  Organic acceptable

Weed Control:

Glyphosate (Round-Up) and Horticulture Vinegar were tested in a vegetable field in Portage on 4 inch and bigger plants. Unreplicated testing showed that just one application of Round-Up Weather Max (540g a.i.) at 1/2 L/acre rate was sufficient to control weeds for about 4 weeks. The Round-Up treatment was slow to show effect on the plants. The Horticulture Vinegar rapidly desiccated the foliage, but the plants showed regrowth again. A second application was needed to control the regrowth; suggesting that the roots of larger plants may remain unaffected. Trials with replication may need to determine effective timing and weed stage for good weed control. Preliminary observations suggest that Horticulture Vinegar could be useful in organic production fields, when weeds are small and repeated applications may be needed for season long management of weeds.

 Vinegar vs Round-Up test plot

No control - Vinegar - Roundup test plot


In general the cabbage crop is looking good. However, rains in the previous two weeks have favoured development of sclerotinia disease in a few crops, including cabbage. Rotation with non-host crops, like cereals for 2-3 years could help reduce the disease levels. Serenade Max and Contans (Bio-fungicide) are registered on cabbage and a number of other crops. Please consult pesticide labels before use.

Sclerotinia headrot of cabbage


As yet there are no confirmed late blight cases in Manitoba. There are however some late blight look-a-likes. Within the lower moist canopy many spots of Botrytis infections can be seen. Please check the link for photos comparing Botrytis vs Late blight leaf spots. http://mbpotatoes.ca/index.cfm

There are a few wilting plants in the field and close examination has shown blackleg infection on the stems. Blackleg disease on potatoes is favoured by wet conditions, and is caused by soft rot bacteria. The bacteria often cause soft rotting of tubers in storage.


Wilting caused by blackleg on potato stem


Blackleg symptom on potato stem 


Compiled by:
Dr. Vikram Bisht, Horticulture Crops Plant Pathologist
Manitoba Agriculture, Food and Rural Initiatives
Phone: (204) 745-0260
Fax: (204) 745-5690
Tom Gonsalves, Vegetable Crops Specialist
Manitoba Agriculture, Food and Rural Initiatives
Phone: (204) 750-1630
Fax: (204) 745-5690

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