Vegetable Crop Insect Management

Joanne Whalen, Extension IPM Specialist;

Brown Marmorated Stink Bug
Although populations were lower the previous two springs due to colder overwintering conditions, it appears that populations could be higher this season. Although trap catches in Delaware are not as high as they were during outbreak years, this year we are seeing a more consistent number in our light traps and pheromone traps located on small vegetable farms compared to 2014 and 2015. A new guidance document titled Integrated Pest Management for Brown Marmorated Stink Bug in Vegetable Crops authored by the BMSB SCRI CAP Vegetable Crop Commodity Team, has been posted to the website. It provides a summary of what researchers have learned so far and management recommendations using an integrated approach.

Although populations of cucumber beetles vary from field to field, higher populations are present in fields with a history of problems. Fresh market cucumbers are susceptible to bacterial wilt that is vectored by the beetles, so treatments should be applied before beetles feed extensively on cotyledons and the first true leaves. Although pickling cucumbers have a tolerance to wilt, a treatment may still be needed for machine-harvested pickling cucumbers when 5% of plants are infested with beetles and/or plants are showing fresh feeding injury. A treatment should be applied for aphids if 10 to 20 percent of the plants are infested with aphids with 5 or more aphids per leaf.

Continue to scout all melons for aphids, cucumber beetles, and spider mites. When fields are blooming, be sure to consider pollinators when making an insecticide application as well as read all labels for pollinator protection statements and restrictions. This past week, we started to see an increase in spider mite populations in the earliest planted fields. The threshold for mites is 20-30% infested crowns with 1-2 mites per leaf. Acramite, Agri-Mek, Oberon, Portal and Zeal are miticides labeled on melons for mite control. Be sure to read all labels carefully for rates and restrictions since some are restricted to only one application as well as ground application only.

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 .

Continue to scout fields for Colorado potato beetle (CPB) and leafhoppers. Adult CPB as well as the small and large larvae can now be found. 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 one third. As a general guideline, once corn borer catches reach 2 per night, fresh market and processing snap beans in the bud to pin stages should be sprayed for corn borer. Sprays will be needed at the bud and pin stages on processing beans. After the pin spray on processing beans, the spray schedule will be determined by a combination of moth catches for corn borer and corn earworm and field scouting.

Sweet Corn
Continue to sample seedling stage fields for cutworms and flea beetles. You should also sample whorl through pre-tassel stage corn for corn borers and corn earworms. A treatment should be applied if 15% of the plants are infested with larvae. The first silk sprays will be needed for corn earworm as soon as ear shanks are visible. Be sure to check both black light and pheromone trap catches since the spray schedules can quickly change. Trap catches are generally updated on Tuesday and Friday mornings on our website. You can also call the Crop Pest Hotline for the most recent trap catches: (302) 831-8851