Based on grower accounts during our winter Extension meetings in various counties, brown marmorated stink bug (BMSB) problems have increased in many areas within the state. The mild winter also favored higher survival of BMSB, as well. So, home gardeners and crop producers alike should be on the watch for this invasive pest as the season progresses. BMSB can damage all of our fruit crops, many vegetables, as well as corn and soybeans. It also will attack many different types of ornamental and wild host plants in the landscape (Figure 1).
BMSB is considered a highly mobile pest, moving frequently from plant type to plant type across the landscape and farmscape. Its movement is influenced by plant stage, phenology, and seasonal progression. On the farm, it is attracted to many of its hosts as the seed heads or fruit structures begin to develop. On diverse farms, it can move to different crops almost on a weekly basis. Damaged caused by BMSB depends on the type of plant it feeds upon with its piercing-sucking mouthparts. Damage can range from shriveled and discolored seeds to discolored corky areas in the flesh of fruit (Figure 2).
There are several BMSB traps that are commercially available to monitor populations in the field. These include 4-foot black pyramid traps (Figure 3) and clear panel traps hung at the same 4-foot height. We are comparing those two trap types in Lexington and Princeton this year. These traps use aggregation pheromones to attract BMSB, but research has demonstrated that they often increased damage adjacent to these traps. It is best to place the traps just outside of the field, preferably along a tree line from which BMSB is likely to invade. Thresholds are still being develop based on numbers of trapped stink bugs, but ten BMSB per trap per week has been used as a threshold for control with apples when using the black pyramid trap.
BMSB is more difficult to control with insecticides than our other stink bug pests. Some of the pyrethroids, such as bifenthrin, fenpropathrin, and cyfluthrin, work well. Some of the neonicotinoids including dinotefuran, clothianadin, and thiamethoxam also work well. For homeowners, malathion is another alternative. Be sure to read the labels and only use insecticides appropriate to plants being treated.
In a home garden situation, fine netting can be used to keep BMSB from injuring produce. We have found that insect netting with holes at least 1/6 inch or smaller can be used to keep BMSB off plants. The netting needs to be in place before BMSB is attracted to the plants and should cover the plant entirely to the ground. The netting should be weighted down on the edges to prevent BMSB from crawling underneath.
There are a number of insects that feed on BMSB eggs including lady beetles, katydids, and damsel bugs. Some of our native tiny wasp parasitoids (Figure 4) also attack the eggs, but at very low levels. Recently a Chinese wasp, which can provide high levels of parasitism of BMSB eggs, was discovered in the states of Maryland and Washington. UK entomologists will be surveying for this beneficial natural enemy of BMSB this year and next in Kentucky.
By Ric Bessin, Extension Entomologist