The double-edged sword of biological control: The bean plataspid (Megacopta cribraria) and its predators in cotton and soybeans

The bean plataspid, Megacopta cribraria (Hemiptera: Plataspidae) was discovered in the United States in 2009 in northeast Georgia and has become a significant pest, invading seven states since its arrival. Bean plataspids consume a wide array of plants, most notably soybean and kudzu and present a major problem for the soybean growing regions of the United States. In addition to being a pest in soybean, they are also a beneficial insect in the context of an invasive weed, kudzu. They have a large impact on stands of kudzu and may be a very important biological control agent for kudzu. This further complicates the status of the bean plataspid. This complication however does not lessen the need to investigate biological control of the bean plataspid. Their predators are poorly understood and in need of investigation. As field observation of predation is difficult, molecular gut content analysis offers an alternative to traditional approaches. Consequently, species-specific 16S molecular markers were designed and used to discern the gut contents of potential predators of the bean plataspid. Various predators were collected throughout the summer in cotton and soybean in southeastern Georgia, and predation frequency was examined relative to prey availability. Predation rates were not affected by prey availability. Our results showed that the bean plataspid was consumed primarily by the predators Geocoris spp, Orius insidiosus, Coleomegilla maculata and several spider groups. These data suggest generalist predators could provide valuable biological control of bean plataspids, but additional research examining the spatio-temporal nature of predator-prey interactions is required to understand the structure of such food webs relative to pest management.