Bill Cissel, Extension Agent – Integrated Pest Management; bcissel@udel.edu
Congratulations Julie Knudson for correctly identifying the damage in the photo as soybean leafminer damage and for being selected to be entered into the end of season raffle for $100 not once but five times. Everyone else who guessed correctly will also have their name entered into the raffle. Click on the Guess the Pest logo to participate in this week’s Guess the Pest challenge!
Guess the Pest Week #17 Answer: Soybean Leafminer
By David Owens, Extension Entomologist, owensd@udel.edu
This week’s Guess the Pest is an interesting but rather unimportant member of the defoliating insect complex. The soybean leafminer (Odontota horni) adult is a beautiful red, flattened, rectangular beetle with red wings and prothorax and black head, antennae, legs, and a black stripe down the middle of the back. The black stripe doesn’t reach all the way to the end of the wings. Adults are active beginning around early to mid-June. They lay eggs on the underside of leaves, and the larvae immediately mine into the leaf. Larvae spend their entire lives between the upper and lower leaf surface, leaving a quarter sized brown blotch. When larvae complete development, they pupate in the mine. Immatures require 30 – 40 days to fully develop into adults. There is only one generation per year. Beetles will continue to lightly skeletonize leaves and over the course of their adult life might feed on the equivalent of one leaflet until they migrate out of fields to find overwintering shelter in late summer. Beetles and larvae are never present in any significant populations.
There are a couple of other beetle leafminers that you may see this summer. The most obvious and abundant is the locust leafminer, Odontota dorsalis. It pretty much stays confined to locust and can cause a large amount of locust defoliation by August. So, as you drive along the highway and notice trees with a brown cast to them, you may be seeing locust leafminer. Locust trees can handle the defoliation and leaf back out.