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Ministry of Agriculture, Food and Rural Affairs

ONION Pest Activity in Ontario

The periods of pest activity illustrated below are general guidelines based upon both Ontario field experience and pest biology research. The actual period of activity for any given pest will vary significantly from year to year, depending on over-wintering conditions; seasonal temperature accumulation; relative humidity; rainfall; prevailing wind patterns; and other environmental factors.

Click on pest name for more info.

Onion Pest Activity Onion Smut Botrytis Leaf Blight Pink Root Downy Mildew Purple Blotch White Rot Slippery Skin, Sour Skin and Soft Rots Neck Rot Iris Yellow Spot Virus Bulb and Stem Nematode Onion Maggot Onion Thrips Leek Moth Cutworms Wireworms Leafminers
Blue Bar Off-peak Pest Activity. The pest may or may not be present at the times indicated. Scouting and other integrated pest management activities performed during the off-peak periods may effectively help to identify and manage pest problems as they begin to develop.
Red Bar Peak Pest Activity. All IPM strategies (scouting, trapping, preventative measures, etc...) should be implemented well in advance of the expected peak activity period. Scouting activities are often intensified during the expected peak periods.