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

The brown marmorated stink bug (BMSB) is an invasive insect that damages around 300 types of plants and crops. Because organic farmers are limited in what products and practices they can utilize against the BMSB, research is needed to provide more options. This study surveys for native natural enemies of BMSB and native stink bug eggs and tests the effectiveness of exclusionary netting and biological control options. The exclusionary component investigated the effectiveness of screens with different mesh sizes placed over crops to exclude BMSB while possibly allowing the entry of natural predators and ample sunlight. Yellow sticky cards detected the presence of natural predators within plots and harvests of the plots measured the marketability and levels of damage on the crop. For natural enemy surveys, BMSB and native sentinel egg masses were placed in a pepper field then collected after a few days and subsequently analyzed to evaluate the rates of parasitism, predation, and hatching of the eggs. Lastly, the entomopathogenic fungus, Beauveria bassiana, was sprayed into field cages and its effectiveness on BMSB nymphs placed inside the cages was evaluated. Results from the screen trials indicate that finer mesh screens produce less fruit but of more marketable quality than larger mesh screens or uncovered plots. Certain natural predators (e.g. Syrphidae) were found in lower numbers inside finer mesh plots. For the natural enemy surveys, parasitism was observed at a moderate level but with almost no successful emergence and predation was almost nonexistent. Because a large portion of BMSBs were not recovered from the B. bassiana cages, the fungus’s effectiveness could not be accurately determined. This study concludes that there are tradeoffs between yield and marketability when utilizing fine screens to protect crops and native enemies do not seem to significantly or sustainably control the BMSB at this time.