Vegetable Crop Insect Scouting

David Owens, Extension Entomologist,

Cucumber beetles continue to be very active. In a late May planting at Carvel, beetle populations exceeded 2-5 per plant and they defoliated a couple of scattered plants. Fields that are flowering and have bees on them should be able to withstand larger populations, and Purdue recommends a threshold of 5 per plant. Be sure to check on these fields in July for new beetle emergence. Fields where a treatment is warranted can be treated with a neonicotinoid through the drip unless there are bees on the field or if you will have bees foraging in the field within 2 weeks. Our best foliar treatment for fields with or near bee-placement is acetamiprid or premix products containing acetamiprid.

Two spotted spider mites are also beginning to move into fields. So far, we have only seen very low, isolated numbers, but if a field has a large number or widespread mite populations, it may have come from a greenhouse infestation. Mite populations are also building up in pokeweeds. Over the last several years, the best active ingredient in our spray trials has been abamectin. However, abamectin is also pretty hard on bees, read the label carefully before using it. You can view 2018, 2019, and 2020 miticide trial data at our website: and read more on spider mite management in various crops using the link in the soybean insect scouting paragraph.

Snap Bean
Scout now for leafhopper; thresholds are 100 adults and nymphs per 20 sweeps. If a spray is warranted, there are a variety of active ingredients to choose from, including pyrethroid, carbamate, OP, neonic 4A and 4D materials. Bean leaf beetle are also active, treat when defoliation reaches 20%. BLB feeding injury can look like someone took a hole punch to the leaves.

Sweet Corn
Moth counts continue to increase. We are forecast for a brief cooldown this weekend and then another brief cooldown mid-week. This is important because we advise spray thresholds be tightened by 1 day when temperatures are above 80 degrees.

We have begun vial testing for pyrethroid resistance. This week, 7 out of 40 treated moths survived for 18% survivorship. This is a little bit lower than where last year started. However, this WILL change, and vial testing will continue through August/early September.

Traps in our moth trapping network are checked Mondays and Thursdays by Richard Monaco. Within 24 hours, data should be uploaded to the UD Pest Management Insect Trapping website. Thursday trap counts are similar, perhaps slightly less than last week and are as follows:

Trap Location BLT – CEW Pheromone CEW
3 nights total catch
Dover 0 25
Harrington 1 8
Milford 2 36
Rising Sun 0 3
Wyoming 0 19
Bridgeville 0 9
Concord 1 21
Georgetown 0 4
Greenwood 0 15
Laurel 1 24
Seaford 0
Lewes 0 48