Alternative Strategies for Managing Megacopta cribraria (Fabricius) (Hemiptera: Plataspidae) in Soybean

Abstract

Megacopta cribraria (F.) (Hemiptera: Plataspidae) commonly known as kudzu bug was introduced from Asia into Georgia, United States in 2009. Its distribution since then has expanded to 12 other states from Arkansas to Washington D.C. Megacopta cribraria is a pest of soybean (Glycine max) Merrill, the second most planted field crop in the United States with an estimated annual market value of about $39 billion. Nymphs and adults of M. cribraria aggregate in large numbers on tender stems or leaves of soybean where they suck sap, resulting in significant yield loss, up to 60%. As the threat posed by this invasive insect pest increases, no effective control strategies other than chemical insecticides are currently available to help soybean farmers. This increased use of chemical insecticides is not sustainable and could result in the development of pesticide resistance. To find alternative control strategies, this study explored the prospects of trap cropping and use of semiochemical attractants for management of M. cribraria. The specific objectives were to: 1) evaluate host plant preference and identify attractive trap crops for M. cribraria; 2) identify plant-based semiochemical attractants for M. cribraria; and 3) identify semiochemical attractants for the egg parasitoid, Paratelenomus saccharalis (Hymenoptera: Platygastridae) (Dodd). In a multiple-choice screen house preference test, M. cribraria showed differential attraction to phenological stages of legume cultivars tested. Soybean, Glycine max (L.) Merr, speckled bean, Phaseolus lunatus L., and lima bean, Phaseolus limensis L., which were identified in screen house tests as attractive to M. cribraria at different phenological stages were further evaluated in the field as potential trap crops at two planting dates; two weeks before main crop (May 24) and same time as main crop (June 7). Soybean trap crop planted on either dates was the most effective at intercepting M. cribraria. The role of volatile organic compounds (VOCs) in host location by M. cribraria as well as the response of its egg parasitoid, P. saccharalis to host-associated odors was investigated. Female M. cribraria did not respond significantly to headspace volatiles of host plants in olfactometer studies. Also, in follow up multiple-choice cage experiment and olfactometer bioassays conducted in the dark, M. cribraria did not make a choice among the plant treatments tested. This implies that host location or preference by M. cribraria is either not mediated by olfactory cues or probably mediated by multiple modalities including visual and olfactory cues. In contrast, female P. saccharalis (egg parasitoid) showed significant attraction to host-associated odors in Y-tube olfactometer studies including damaged soybean, damaged soybean plus M. cribraria eggs and M. cribraria eggs only, suggesting that host location by the egg parasitoid is mediated by odor cues from soybean and M. cribraria eggs. A new egg parasitoid was recovered from parasitized M. cribraria eggs collected on soybean in Auburn, AL during summer 2016. Parasitization rate ranged from 82 - 100%. The identity of this new egg parasitoid is currently unknown and voucher specimens have been sent to the Smithsonian Institute, Washington D.C. for accurate identification. It is hoped that results from this research will enhance the economic viability of soybean and legume crop production by developing ecological-based management tools for managing M. cribraria in soybean.