Root, bulb, leafy and brassica vegetable pest report – 21 August 2012

The threshold for third generation emergence of onion maggot flies has been reached in Delhi and Bradford/Holland Marsh and should be reached in 10-12 days in Wellington (previously reached in Windsor, London and Thedford). Over the past week, onion thrips counts have been increasing in some onion fields, as reported by the Muck Crops Research Station.  From earlier this week, DOWNCAST indicated that the risk of downy mildew on onions was moderate to high; however, it has dropped to moderate as the week progresse. No downy mildew cases have been reported. DOWNCAST is not available in other areas of Ontario, thus protective fungicides should be applied during cool, humid conditions.

As previously mentioned, the threshold for emergence of second generation carrot rust fly has been reached in all areas. Earlier this week, carrot rust fly activity was still high in some areas of the Holland Marsh, especially in more sheltered areas. Carrot rust fly activity has slowed down as the week progresses.

Degree day accumulations indicate peak of third generation cabbage maggot in Delhi, London and Thedford (in 4-5 days for Wellington).  Please let me know if you are seeing Swede Midge damage this season. Contact Marion Paibomesai at marion.paibomesai@ontario.ca, 519-826-4963.

Here are the degree days accumulated from April 1st until August 21st, 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