Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu
Delaware does not have the acres of peppers we once had but it is still an important crop. The following are several disease control suggestions from Andy Wyenandt from Rutgers University that are timely.
Bacterial leaf spot
Bacterial leaf spot has been found. Symptoms of bacterial spot on pepper leaves include small, brown water-soaked lesions that turn brown and necrotic in the centers. Spots may coalesce and form large blighted areas on leaves and premature defoliation can occur. On fruit, brown lesions can form which have a roughened, cracked, wart-like appearance. High temperatures, high relative humidity and rainfall favor bacterial spot development. Losses from bacterial spot can be reduced somewhat by maintaining high levels of fertility, which will stimulate new growth. Applying a fixed copper (M1) at labeled rates plus maneb (M3) at 1.5 lbs 75DF/A or 8.0 to 10.0 oz Tanos (famaxodone + cymoxanil, 11 + 27) may help suppress spread. For more information on control of bacterial leaf spot of pepper please see the Delaware Commercial Vegetable Production Recommendations.
Phytophthora Blight on Pepper
For control of the crown rot phase of blight, broadcast prior to planting or in a 12 to 16-inch band over the row before or after transplanting:
1.0 pt Ridomil Gold 4E/A,
or
1.0 qt Ultra Flourish 2E/A (mefenoxam, 4),
or
MetaStar (metalaxyl, 4) at 4.0 to 8.0 pt 2E/A.
Make two additional post planting directed applications with 1 pint Ridomil Gold 4E or 1 qt Ultra Flourish 2E per acre to 6 to 10 inches of soil on either side of the plants at 30-day intervals. Use the formula “Calibration for Changing from Broadcast to Band Application” on page E6 in the Pest Management Section of the Delaware Commercial Vegetable Production Recommendations to determine amount of Ridomil Gold needed per acre when band applications are made. When using polyethylene mulch, apply Ridomil Gold 4E at the above rates and timing by injection through the trickle irrigation system. Dilute Ridomil Gold 4E prior to injecting to prevent damage to injector pump.
Anthracnose on Pepper
Symptoms of fruit infection include sunken, circular spots which develop blackish-tan to orange concentric rings as lesions develop. Lesions on stems and leaves appear as grayish brown spots with dark margins and can easily be overlooked. Control of anthracnose begins with scouting on a regular basis and applying preventative fungicide applications before symptoms appear, especially in fields or areas of your farm where you have had anthracnose problems in the past. Beginning at flowering and as small fruit begin to set, alternate maneb (M3) at 1.5 to 3 lb/A 75DF with one of the following FRAC code 11 fungicides:
azoxystrobin (Quadris at 6.0 to 15.5 fl oz 2.08F/A),
or
Flint (trifloxystrobin) 50WDG at 3.0 to 4.0 oz/A,
or
Cabrio (pyraclostrobin) 20EG at 8.0 to 12.0 oz/A,
or
Tanos (famaxodone + cymoxanil, 11 + 27) at 8 to 10 50WDG/A.
After harvesting, pepper fields should be disked and plowed under thoroughly to bury crop debris.
Anthracnose on pepper fruit