Development of Behavior-semiochemical-based IPM Approach for Invasive Kudzu Bug, Megacopta cribraria (F.) (Hemiptera: Plataspidae)
Type of DegreePhD Dissertation
Entomology and Plant Pathology
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The kudzu bug, Megacopta cribraria (F.), is newly detected invasive pest insect native to Asia. Since the first detection in 2009, it has spread rapidly throughout the southeastern U.S. It has become a key pest of legume crops, particularly soybeans (Glycine max L.), and a threat to the international trade of agricultural produces. However, chemical insecticides are currently the only tool to control M. cribraria. The searching for alternative IPM approaches to control M. cribraria based on manipulating behavior and programs exploring semiochemicals against M. cribraria are needed, both for the preservation of the environment and from an economic point of view. In this study, we first investigated the effect of plant growth stage on the attraction of adult M. cribraria to soybeans, and whether the attraction was plant constitutive volatiles. Greenhouse assays examined behavioral orientation preference of adults when given choices of four growth stages of whole soybean plants (V2, R1, R3, and R5). Significantly more adults landed on the early reproductive stage R1, followed by R3, compared with V2 and R5 stages. Laboratory olfactometer assays elucidated that plant constitutive volatiles were the cues used by adult M. cribraria in locating and selecting the preferred growth stage. Females were significantly more olfactory sensitive than males. Electroantennogram (EAG) results indicated strong antennal responses to constitutive volatiles emitted by the whole soybean plant, though the antennal olfactory responses were not statistically different among volatiles of different growth stages. Then, two greenhouse choice assays were conducted to evaluate the foraging orientation preference of M. cribraria adults to six legume species and to plant growth stages (V2, V4, R1 and R5) of each plant species. The R1stage was the most attractive in soybean and lima bean (Phaseolus lunatus (L.), whereas the preferred stage varied for the other legumes. iii Given their respective attractive growth stages, adults significantly preferred lima bean over soybean and kidney bean (Phaseolus vulgaris (L.), but showed little interest in other legume species. Two greenhouse no-choice assays assessed the suitability of the six legumes for adult fecundity and nymph development. Though oviposition occurred to females caged with every legume species and no significant differences in the number of eggs among the species, females showed ovipositional preference to soybean, lima bean and mung bean plants. The hatch rates of eggs laid by adults fed on soybean, lima bean and mung bean were significantly higher than other legumes. Nymphs completed development only on soybean, lima bean, and mung bean, but the survivorships were significantly greater on soybean and mung bean than on lima bean. Lastly, electrophysiological and behavioral responses of adult M. cribraria to plant volatile compounds from kudzu (Pueratia montana (Loureiro) Merrill var. lobate (Willdenow)) and soybean, were examined to identify plant semiochemicals used in host location and attraction of M. cribraria. Analysis of the headspace volatiles of the kudzu and soybean plants by gas chromatography-electroantennographic detection (GC-EAD) with female M. cribraria revealed six compounds that elicited antennal response. The host volatile compounds were identified using gas chromatography-mass spectrometry (GC-MS). EAG from female M. cribraria were recorded in response to 15 compounds. Among them, 1-octen-3-ol, nonanal, ocimene and benzaldehyde, eliciting the strongest EAG responses were selected to evaluate the dose-dependent EAG responses and behavioral responses to M. cribraria. The host plant chemicals, 1-octen-3-ol and benzaldehyde were significantly more attractive to M. cribraria at higher doses in EAG and olfactometer bioassays, indicating a dose-dependent effect. Our results provide an insight into M. cribraria chemical and behavioral ecology and is of great significance for optimal iv timing of field scouting and treatment, and the development of semiochemical-based management of M. cribraria.