Vegetable Crop Insect Scouting

David Owens, Extension Entomologist,

Sweet Corn
Trap results continue to be inconsistent throughout the state. Georgetown has been experiencing very low to relatively low moth activity while many other sites have normal or above average moth activity. It takes eggs 3 days to hatch when the high temperatures are below 82 to 85 degrees. Sweet corn at first silk through the first week of silking may need to be on a 2-day spray schedule if local traps are indicating very high moth activity. Traps placed by your sweet corn will give you the best indicator of moth pressure, I have seen traps placed less than a quarter mile from each other indicate radically different activity, so only use the below to get an idea of trends.

Thursday Trap results are as follows:

Trap Location BLT – CEW Pheromone CEW
3 nights total catch
Dover 3 149
Harrington 3 55
Milford 6 157
Rising Sun 3 58
Wyoming 3 59
Bridgeville 1 60
Concord 3 136
Georgetown 44
Greenwood 3  
Laurel 3 131
Seaford 2 54
Lewes 6 81
Millsboro 3 2

Spider mites have dropped off in the fields we have been looking at. The biggest threat to cucurbits now might be aphids and squash bug on late summer squash and pumpkins. In high numbers they can cause leaf curling and distorted or slowed growth, spread viruses and coat developing fruit in honeydew which leads to unsightly sooty mold growth. While the weather has not been conducive to mites, it has been conducive to aphids. Be sure to carefully scout fields that have been treated with pyrethroids. Pyrethroids generally keep natural enemy activity low, unless you are in my melon field where I have sprayed 4 times and still have ladybugs. On the other hand, pyrethroids are very useful against squash bugs. Treat when you have 1 hatching egg mass per plant. If you have to treat for squash bug, you may need to come in with a follow up spray about a week later to clean up any other egg masses that hatched after the first application. Other materials that will get both squash bug and aphids are Assail and Sivanto. Also check your late cucurbits for cucumber beetles. Second generation beetles have begun emerging from the soil and will sometimes congregate on the last remaining cucurbit growth heading into winter.