Cause Erysiphe pisi (= Alphitomorpha pisi = Ischnochaeta pisi; anamorph Oidium arachidis), a fungus that can be seedborne but usually survives as conidia on living plants. Normally the disease does not cause serious losses if peas are planted in spring or an early-maturing cultivar is planted. When peas are recropped on the same ground, the fall planting sometimes develops problems.
Symptoms The first symptom is powdery white mycelium and spores on leaf and stem surfaces. On some cultivars, affected areas may die. All cultivars are dwarfed if infested early. Affected pods of some cultivars, including Oregon Sugar Pod, develop small brown to black necrotic spots.
- Plant early-maturing cultivars.
- Many resistant cultivars are available.
- Plant early in the growing season.
- Rotate plantings at least 1 year.
- Bicarbonates are registered to control powdery mildew. Thorough coverage is essential.
- Kaligreen at 2.5 to 3 lb/A on 7- to 10-day intervals. May be applied up to the day before harvest. 4-hr reentry. O
- MilStop (85% potassium bicarbonate) at 2 to 5 lb/A. 1-hr reentry.
- Cinnacure at 0.25 to 1 gal/A on 7- to 1-day intervals. 4-hr reentry.
- Copper products are not effective as stand-alone materials. Care must be taken to avoid build-up in the soil.
- Champ WG at 1.58 lb/A on 7-day intervals. 48-hr reentry. H O
- Cueva at 0.5 to 2 gal/100 gal water on 7- to 10-day intervals. May be applied on the day of harvest. 4-hr reentry. O
- Cuprofix Ultra 40D at 1 to 2 lb/A on 7- day intervals. 48-hr reentry.
- Kocide 2000 at 1 to 2.25 lb/A or Kocide 3000 at 0.5 to 1.25 lb/A on 7-day intervals. 48-hr reentry.
- Nu Cop 50 WP at 1.5 lb/A on weekly intervals. Do not apply within 1 day of harvest. 48-hr reentry. O
- Endura (Group 7) at 8 to 11 oz/A on 5- to 14-day intervals. Do not feed treated pea commodities to livestock. Preharvest interval is 21 days for dried peas and 7 days for succulent peas. 12-hr reentry.
- Milstop (85% potassium bicarbonate) at 1 Tbsp/gal water on 7- to 14-day intervals. May be applied on the day of harvest. 1-hr reentry. H O
- OSO 5% SC (Group 19) at 3.75 to 13 fl oz/A on 7- to 14-day intervals. Can be applied the day of harvest. 4-hr reentry.
- Sulfur formulations are registered. Sulfur is fungitoxic in its vapor phase and, therefore, is effective only when air temperatures promote volatilization. Sulfur volatilizes above 65°F but becomes phytotoxic above 95°F. Using it above 85°F is not recommended. Although sulfur reduces sporulation of established infections, it is primarily a protectant and must be applied before infection. Begin applying when weather conditions are appropriate and continue at weekly intervals.
- Bonide Sulfur Plant Fungicide RTU is available for home gardens. H O
- Microthiol Disperss at 7 lb/A on 14-day intervals. 24-hr reentry. O
- Sulfur 6L (52% sulfur) at 3 to 7 pints/A. 24-hr reentry.
- Trilogy at 0.5% to 1%. Do not use above 90°F or when plants are under heat or moisture stress. Do not use when foliage is wet as good coverage is essential. Poor control as a stand-alone product. 4-hr reentry. O
Biological control Efficacy unknown in the Pacific Northwest.
- Double Nickel LC at 0.5 to 6 quarts/A on 3- to 10-day intervals. Can be applied the day of harvest. 4-hr reentry. O
- Regalia at 1 to 4 quarts/A plus another fungicide on 7- to 10-day intervals. Preharvest interval is 0 days. 4-hr reentry. O
- Sonata at 2 to 4 quarts/A on 7- to 14-day intervals. Can be applied up to and on the day of harvest. 4-hr reentry. O