Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu
Brown marmorated stink bug populations were a big concern early this spring (and also all of last year) as their numbers were found to be pretty high in and around fruit orchards and a few vegetable fields. These were the BMSB that had overwintered that were coming out of their hibernation mode and moving out for something to eat. Their populations grew a bit more in May, but then seemed to hold steady, except for some scattered hot spots throughout the Mid-Atlantic where their numbers and damage were much greater. For the most part, growers were ready for the onslaught and did a good job of limiting the bug’s damage, but at the cost of a heavy spray schedule and the loss of many of their IPM programs. The adult BMSB population has declined over the last few weeks in many areas of the Mid-Atlantic. I am guessing that some of the overwintering adults are dying off and that soon the nymphs will start to be seen in greater numbers than before. This is just what I see happening in some pepper fields. Where before we were finding few adults or egg masses, we now are finding 4-6 nymphs/plant (Photo 1). The nymphs are feeding on both large and very small fruit causing damage that looks much like what the adults would do to peppers (Photo 2). BMSB eggs were looked for earlier in the season and not found to any great extent, but the eggs of any stink bug are very difficult to find. That is why there still are no good thresholds for green and brown stink bugs in many vegetable crops—they are just too difficult to monitor accurately. These medium-size nymphs we are now seeing are easy to spot as they tend to be on the top or edge of the pepper plants in the morning and even during early afternoons. Growers should be looking for the nymphs now in all their vegetables, but especially in peppers and sweet corn even if they have not seen many BMSB adults before this time. These medium to small nymphs while not particularly easy to kill are much easier to control than large nymphs or the adults and this would be the time to control them.
Photo 1. Brown marmorated stink bug nymph
Photo 2. BMSB feeding damage on small and medium size pepper fruit