Degree days for root, bulb and leafy vegetable pests – 4 July 2012

Thresholds for second generation emergence of onion maggot flies have been reached in the London area and is expected to be reached in Thedford, Delhi and Bradford/Holland Marsh over the next 2-4 days. Peak of second generation of cabbage maggot flies has been reached in London area. If resident populations are present, second generation of carrot rust fly adults should start emerging in the Windsor area.

Stemphylium leaf blight and purple blotch has been seen on onion in the Holland Marsh. These diseases are often found on leaves damaged by other diseases, insects or environmental stresses. Onion thrips counts are also increasing in the Holland Marsh. Keep an eye on aster leafhoppers. Over the past couple weeks, infectivity has been high in Michigan (ranging from 5.2—12.9%).

Here are the degree days accumulated from April 1st until July 4th, 2012.

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

Degree day model information for pests