Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu
Asparagus
If you are still cutting asparagus, continue to watch for asparagus beetle adults laying egg masses and feeding on spears. Feeding by beetles can disfigure spears and the presence of eggs on the spears can make them unmarketable. As a general guideline, a treatment is recommended if 2% of the spears are infested with eggs or if 5% of the plants are infested with adults. Once ferns are present, larvae can also defoliate plants. As a general guideline, a treatment may be needed if 50 % of the plants have larvae or you can find 10% defoliation.
Melons
Continue to scout all melons for aphids, cucumber beetles, and spider mites. The treatment threshold for aphids is 20% infested plants with at least 5 aphids per leaf. Be sure to also watch for beneficials. The threshold for mites is 20-30% infested crowns with 1-2 mites per leaf. We continue to see an increase in cucumber beetle activity. Since beetles can continue to re-infest fields, as well as hide under the plastic, multiple applications are often needed.
Peppers
The earliest planted fields should be sampled for thrips and corn borer egg masses. Corn borer moth catches remain low in light traps. Before fruit is present, young corn borer larvae can infest stems and petioles. Be sure to also 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
Fields should be scouted for Colorado potato beetle (CPB) and leafhoppers. Adult CPB as well as small larvae can now be found in fields not treated at planting. 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 on half 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 one third.
Sweet Corn
Continue to sample seedling stage fields for cutworms and flea beetles. You should also sample all whorl stage corn for corn borer and corn earworm larvae. We found our first corn earworm moths in the pheromone traps this past week. A whorl stage treatment should be applied if 15% of the plants are infested with corn borer or corn earworm.