David Owens, Extension Entomologist, owensd@udel.edu
Last week’s guess the pest was a bit tricky, as there are a couple of things that can cause wilted leaves. Whenever a whorl is dead but the lower leaves appear healthy, it indicates the growing point has been killed under ground. In this particular case, there is also a strip of yellow on one side of the lower leaf blade. Digging this plant up revealed a small hole near the base, most likely caused by wireworm, and both symptoms are characteristic of wireworm injury. Seed treatments generally do a good job even at low rates, although there is a rate response. In previous years we have seen only a small difference between Poncho 250 and P500. UMD entomologist Dr. Kelly Hamby estimates that the cost of going to a 1250 rate was greater than the inclusion of bifenthrin in the furrow while still providing excellent control. So where should such a heavy hand be applied? Sample fields either in the fall or spring for wireworm and white grub by digging 8”x8”x6” holes or by baiting a field with a dough ball in spring.