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Vegetable Report: August 17-23, 2013

The crops are growing well and the current levels of aster yellows remains minor, ranging from trace to <1% of plants showing aster yellows symptoms. The Aster leafhopper numbers trapped continue to be low this week also, but numbers appear to be creeping up. There is a sudden resurgence of aphid numbers in insect net sweeps and also yellow cards. The increase may be related to maturity and harvesting of canol and wheat, forcing the aphids to find other hosts.
Insect Net Sweeps ALH on Yellow cards (3X5")
ALH per 100 sweeps
Aug 20
Trapped in 1 week
 Aug 14-20
ALH per sq inch in 1 week
Grower 1, Field 1 1 0.07
Grower 1, Field 2 0.5 0.03
Grower 2, Field 1 18 11 0.73
Grower 2, Field 2 0 2 0.13
Grower 3, Field 1 28
Grower 3, Field 2 88
To date (Aug 21) no late blight has been found in Manitoba on tomatoes or potatoes. Even so, tomato producers using conventional production systems should continue to spray protectant fungicides. Organic producers should continue to apply aproved organic late blight control measures such as the use of copper based foliar sprays. If you have any suspicious tomato or potato plants please send them for identification to the MAFRI Crop Diagnostic Lab at the University of Manitoba Fort Garry Campus (545 University Crescent, Winnipeg, MB). There is a $10 fee charged to non-commercial gardeners for the diagnosis of a sample submitted to the lab.
Field tomatoes will soon be red and ready for market. If you see 4-spotted sap bugs (bear bugs) around any crop, it may be nature's way of indicating that some fruit or plant is rotting in the vicinity. Check for maturing tomatoes touching the ground and rotting within the canopy.
Flea Beetles on Crucifer Vegetables:
Due to heat and the maturity of canola, significant numbers of flea beetles are moving on to other crucifer vegetables. Their movement could impact cabbage, cauliflower, bok-choy and other crucifer vegetables. Some of the pesticide options are: Endosulfan, Thiodan, Thionex, Matador, Pounce, Ripcord, Sevin (various formulations). Please read pesticide product label before use and keep in mind the pre-harvest interval.  

Flea beetles on cauliflower

Flea beetles on volunteer canola (weed)

Most cucurbits appear healthy, with very little powdery mildew. There are a couple of sites however, with powdery mildew.
Edible Beans:
Common blight, a bacterial disease, was noted during early August in some snap beans. This bacterial disease is favoured by high humidity within the canopy and is spread by wind and rain. Foliar copper sprays are an approved control measure. These products have a 1 day PHI which must be respected. The efficacy of using copper products for control of common blight this late in the year has not been very good. Copper sprays work best when applied preventively over the field. If a producer can minimize moving through the plant canopy when it is wet (rainfall, irrigation, and/or dews), this will reduce the spread of common blight.
Sclerotinia (white mould) was also found in snap beans last week both as stem and pod rot. Preventative control measures for Sclerotinia prior to planting include the biological product Contans WG. In field control measures include the foliar application of Allegro and Serenade Max fungicides.
Bulb Onions:
Producers are planning to begin wind rowing onion fields this week. Drying of the onion tops - either in field or using hot air storage, is essential for good quality. A properly dried (cured) onion is less prone to having incidences of disease.
With the overall warmer weather of August, peppers have begun to mature quickly now. The mature peppers observed were sweet banana peppers and green bell peppers. Producers have had to pick fields multiple times in a week to stay ahead of the peppers becoming over ripe and unmarketable. Longer season peppers observed last week such as red bell varieties, are close to maturity.
As yet, there is no confirmed late blight in Manitoba. To check late blight risk to potato and tomato in your area please check: Manitoba Potato Weather Network
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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