Root, bulb, leafy and brassica vegetable pest report – 24 July 2012

The threshold for third generation emergence of onion maggot flies should be reached in Windsor in 5-6 days. Degree day accumulations indicate peak of third generation cabbage maggot in the Windsor area. The threshold for emergence of second generation carrot rust fly has been reached in all areas, except Wellington (likely in 2-3 days).

DOWNCAST, which helps predict downy mildew outbreaks in onions in the Holland Marsh, indicated that the risk of downy mildew on onions is moderate (depends on canopy size of crop). Risk may increase if temperatures cool and leaves remain wet for long periods. DOWNCAST is not available in other areas of Ontario, thus protective fungicides should be applied during cool, humid conditions. Currently, onion downy mildew has not been reported in Ontario.

Here are the degree days accumulated from April 1st until July 24th, 2012.

(These values are provided as guidelines only. Local environments, soil type, field history, etc. may influence activity of these pests.)

*Data provided by Muck Crops Research Station, University of Guelph.

Degree day model information for pests