Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu
Melons
Continue to scout all melons for aphids, cucumber beetles, and spider mites. The threshold for mites is 20-30% infested crowns with 1-2 mites per leaf. With the recent warm weather, cucumber beetle activity has increased this past week. Since beetles can continue to re-infest fields as well as hide under the plastic, be sure to check carefully for beetles as well as their feeding damage. Multiple applications are often needed to achieve effective control.
Peppers
Be sure to sample for corn borers and watch carefully for egg masses. Before fruit is present these young corn borer larvae can infest stems and petioles. As soon as the first flowers can be found, be sure to consider a corn borer treatment. Depending on local corn borer trap catches, sprays should be applied on a 7 to 10-day schedule once pepper fruit is ¼ – ½ inch in diameter. Be sure to check local moth catches in your area by calling the Crop Pest Hotline (302-831-8851) or visiting our website at http://agdev.anr.udel.edu/trap/trap.php .
Potatoes
Continue to scout fields for Colorado potato beetle (CPB) and leafhoppers. A treatment should be considered for adults when you find 25
beetles per 50 plants and defoliation has reached the 10% level. Once larvae are detected, the threshold is 4 small larvae per plant or 1.5 large larvae per plant. As a general guideline, controls should be applied for leafhoppers if you find ½ to one adult per sweep and/or one nymph per every 10 leaves.
Snap Beans
Continue to sample all seedling stage fields for leafhopper and thrips activity. The thrips threshold is 5-6 per leaflet and the leafhopper threshold is 5 per sweep. If both insects are present, the threshold for each should be reduced by 1/3.
Sweet Corn
Continue to sample seedling stage fields for cutworms and flea beetles. You should also sample any early planted whorl stage corn for corn borers and corn earworms. A treatment should be applied if 15% of the plants are infested with larvae.