For the past few weeks, we have been finding a lot of adult brown stink bugs in wheat fields. Most have been found on the edges of fields, next to a tree-line. These are overwintered adults that came into wheat fields after overwintering in nearby weeds. A couple of weeks ago, we began finding a lot of immature stink bugs, nymphs, indicating that a large clutch of egg masses hatched a few weeks ago. We are now seeing 3rd and 4th instar (nearly fully grown) nymphs. This is the first new generation of the summer. Adults from these nymphs will migrate into new host crops, like corn.
We have also noticed that many of the stink bug egg masses are parasitized (see attached image). A natural enemy of brown stink bugs is a tiny parasitic wasp called Telenomus podisi. Females use their ovipositor to lay eggs inside of stink bug eggs, and when the larvae hatch, they eat the developing stink bug embryos. This year, we have found that a very high percentage of stink bug eggs are parasitized which means that hundreds of stink bugs will never hatch. In past years, we conducted stink bug egg parasitoid surveys in Virginia. Results indicated that nearly 50% of all brown stink bug eggs and almost 90% of brown stink bug egg masses were parasitized. We are fortunate that these little natural enemies are working to reduce numbers of this troublesome pest.

(author: Amanda Koppel, Graduate Student, Department of Entomology, Virginia Tech, Advisor, Ames Herbert)
Additional information: parasitoids-008-jpg