Vegetable Crop Insect Scouting

David Owens, Extension Entomologist,

As a reminder, sweet corn trapping information can be found here: Threshold information can be found here: We are currently catching low numbers in some of the blacklight traps.

Cucumber beetles seem to have not yet arrived on melons. Be scouting carefully and vigilantly. With the cool weather, melon plants are small and growing slowly. When the first cucumber beetles find a suitable host plant (and melons are the most abundant cucurbit), they begin producing an aggregation pheromone that draws in more male and female beetles. They will feed ravenously and mate. This activity can occur very quickly, and in a short period of time, beetles can do quite a bit of damage to small transplants. Any neonic in the drip will probably give about 2-3 weeks of residual control. Be sure to follow label guidance on amount of product per 100 ft of drip. If you go by the plastic footprint (so many beds x bed width = area x rate) you will significantly under treat.

Last year, beetles were first observed in Laurel May 14. At Carvel, large numbers were observed on May 20 in melons on the south side of a woodline. On the north side of the woodline, melons of the same age were infested June 6. Bottom line, scout often, especially when the weather warms up, be prepared to treat, and call me before you kill all the beetles! I need a couple thousand for 2020 bioassays.

While checking fields for cucumber beetles, be on the lookout for aphids as well. Large numbers of aphids can result in leaf curling, and aphids can transmit viruses to melons. Another common sign of aphid presence is that of ants on the plants. Aphids excrete honeydew which the ants collect. In turn, ants will often protect aphids from parasitic wasps. Last year, large numbers of melon aphids colonized my transplants beginning in the greenhouse and then more severely once the plants were put out to harden off. Transplant treatment with a neonic will effectively eliminate the aphids. There are special instructions for treating transplants on the labels. Over application may result in phytotoxicity. Overhead watering may be necessary to wash material into the plug, but not so much that it leaches out. Residual efficacy of such a treatment is less than 14 days.

Beware of potential seedcorn maggot damage to direct seeded crops given the relatively cool soil, as well as cabbage maggot in Brassicas. Unfortunately, the best time to treat if adult activity is present is as a preventative treatment.