David Owens, Extension Entomologist; owensd@udel.edu
Watermelon
I found a couple of aphids on my greenhouse transplants and didn’t think too much of them. I set my transplant trays outside to harden off last week and came back to them this week only to find aphids had infested several trays, causing leaf cupping. In most cases, significant parasitoid pressure was present and most aphids were already transformed into parasitoid mummies. Pyrethroids will not affect green peach aphid or melon aphids, there are numerous other products that will do the job, including neonicotinoid insecticides that also pick up cucumber beetle. Cucumber beetles were observed feeding in a field that was transplanted last week. Transplants were treated prior to setting, and beetles were affected and dying. Residual activity generally lasts between 2 and 4 weeks. If chemigating insecticide through the drip tape, figure your rate based on field footprint, not plastic footprint. For example, if a product goes out at 10 ounces/acre and a field is 10 acres, then 100 ounces of product need to be delivered. If you base the rate on the amount of actual plastic (roughly 20-30% of the field area), you could be significantly undertreating! As plants are coming out of the greenhouse, be sure to also check for the presence of two spotted spider mites. On transplants, leaf stippling will be more evident than on older plants.
Sweet Corn
The 2019 insect trapping network has largely been deployed. Trap capture data will be uploaded to the webpage as in previous years, and most recent trapping data presented here when sweet corn is closer to tasseling. You can find trap catch data here: https://agdev.anr.udel.edu/trap/trap.php. We are picking up low numbers of corn earworm, most likely from overwintering pupae and at this point are more of a curiosity. Scout for black cutworm damaging seedlings (3% cut plants or 10% leaf feeding).