Economic thresholds generally do not exist for plant pathogens and nematodes in Idaho field and row crops.  The following table instead lists pesticide application timing recommendations for disease and nematode management.

Onions

Pathogen		Pesticide	Timing
	Botrytis leaf blight (Botrytis squamosa)	Protective fungicides	Apply protective fungicides when conditions are favorable for disease development (cool temperatures between 55° and 75°F and long periods of leaf wetness).
	Downy mildew (Peronospora destructor)	Protective fungicides	Apply protective fungicides when conditions are favorable for disease development (cool temperatures between 55° and 75°F and humid weather).
	Purple blotch (Alternaria porri)	Protective fungicides	Apply protective fungicides when disease occurs to prevent further spread.

References:  Pacific Northwest Disease Control Handbook, 2000.

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