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.

Potatoes

Pathogen		Pesticide	Timing
	Early blight (Alternaria solani)	Protective fungicides	In areas of Idaho where early blight is NOT a perennial problem, apply protectant fungicides when blight lesions occur above the lower third of the plant canopy. In areas of Idaho where early blight IS a perennial problem, apply protectant fungicides at 10- to 12-day intervals from mid-July until mid-August
	Late blight (Phytophthora infestans)	Protective fungicides	Apply protective fungicides every 7 days starting at 6 inches of shoot growth.  If weather, such as rain, favors late blight infection, apply at 5- to 7-day intervals.
	Leak (Pythium debaryanum and P. ultimum)	Protective fungicides (Ridomil Gold Bravo, Ridomil Gold MZ or Ridomil Gold Copper)	Apply protective fungicides (Ridomil Gold Bravo, Ridomil Gold MZ or Ridomil Gold Copper) when plants are flowering.
	Pink rot (Phytophthora erythroseptica)	Protective fungicides (Ridomil Gold Bravo, Ridomil Gold MZ or Ridomil Gold Copper)	Apply protective fungicides (Ridomil Gold Bravo, Ridomil Gold MZ or Ridomil Gold Copper) when plants are flowering.
	Powdery Mildew (Erysiphe polygoni)	Sulfur fungicides	Begin applying sulfur fungicides when mildew if first observed. If necessary, repeat application to maintain 10% or lower leaf area diseased through the growing season.

References:  Pacific Northwest Disease Control Handbook, 2000.

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