Mechanical exclusion and biological control of the brown marmorated stink bug (Halyomorpha halys) in organic agriculture

The brown marmorated stink bug (Halyomorpha halys) is an invasive insect pest that originated from Southeast Asia and was first identified in the United States in Allentown, Pennsylvania. After its introduction, H. halys has spread to 40 states in the U.S., where it causes damage to agricultural and ornamental plants. H. halys also causes a public nuisance by invading buildings for over-wintering sites and by producing a foul-smelling odor when disturbed. H. halys has been recorded feeding on approximately 300 host plants and damages crops by sucking out the plant juices, causing abscission of the crop or feeding wounds that can reduce marketability of crops. Currently, there are no OMRI approved pesticides that provide reliable control for organic farming, so I am investigating other methods for use on  organic farms. In one part of this study, sentinel H. halys eggs and the eggs of native stink bugs were placed in a pepper field and later analyzed for the rate of attack by native predators and parasitoids. The other portion of the study investigated the use of different sizes of netting to cover crops, excluding stink bugs from the crops and allowing the entry of beneficial insects. Exclusionary netting treatments included no net, a 0.42 cm net, a 0.32 cm net and a fine mesh secured over 2 m by 2 m frames. Results of the sentinel egg  study showed that 79% of the H. halys eggs either hatched or showed no evidence of predator or parasitoid attack. Fourteen percent of the H. halys eggs showed evidence of parasitism attack, but the parasitoids did not emerge. In contrast, 62% of the brown stink bug (Euschistus servus) eggs displayed parasitism attempts with a 47% success rate. Results of the exclusion trials revealed that the number of predators within the screens and sunscald damage to the crops both decreased with smaller screen sizes. The incidence of piercing-sucking damage to peppers was highest in uncaged plots and under the 0.32 cm mesh screens. Importantly, the amount of marketable crop within the plots decreased with the screen size due to reduced plant productivity under the netting. However, H. halys levels were quite low in this study. These results suggest that, for now, parasitoids provide lower rates of attack and success with  H. halys eggs. The screen trials demonstrate that finer nets exclude beneficial insects and possibly provide a significant amount of shade that may decrease the amount of fruit produced by the plants. However, they do effectively exclude stink bugs and could provide farmers with an effective level of control in areas or years with high H. halys densities.