Current control of kudzu bugs is dependent on effective coverage and penetration of the canopy with broad-spectrum chemical pesticides, resulting in loss of beneficial insects and pollinators and increasing the risk for mid- to late-season infestations by other devastating pests. A potentially more effective and environmentally safe alternative for the control of kudzu bug would be the use of gene silencing insecticidal technology by RNA interference (RNAi), which has revolutionized pest control in agriculture. The goal of this project is to develop RNAi as a biopesticide to control kudzu bug in transgenic soybean. We plan to develop bioassay methods for kudzu bugs to use in screening of candidate genes for RNAi identified from sequencing the gut transcriptome of the kudzu bug. Once identified, specific genes will be targeted through development of transgenic soybean lines.
The develop of kudzu bugs (Megacopta cribraria) is likely impacted by two important biotic factors. The first is what host plant they develop on, and the second is the presence of a known beneficial, symbiotic bacteria. In the case of Megacopta, the two primary host plants in the United States appear to be kudzu and soybeans. The ability for the Megacopta to utilize different host plants is thought to depend on the presence and genotype of the bacterial symbiont stored in the gut of the insect (Fukatsu & Hosokawa, 2002; Hosokawa et al., 2007). The obligate symbiont present in the Megacopta gut is known to be a bacterium called Ishikawaella capsulata (Fukatsu & Hosokawa, 2002). The transfer of bacteria from one generation to the next is accomplished through the use of a protein capsule manufactured by the mother, loaded with symbiont, and deposited with the egg mass.This novel mode of transmission allows for convenient study of the development and fitness of M. cribraria with and without the symbiont. We are testing how host plants and symbionts interact to impact the development and survival of the kudzu bug. Much of this work is being carried out in field experiments sponsored by the Doraville Unity Garden in Doraville, Georgia.
During the spring and summer of 2012, we will rear M. cribraria from egg to adult emergence, and measure the timing and rate of development, body size at each life stage, and mortality.The experimental design contains four treatments consisting of two host plants, and the presence and absence of the symbiont There is a secondary question that is of agricultural importance, namely the impact of M. cribraria on the growth of soybeans. A subset of the soy will be grown without M. cribraria in order to measure the biomass of these plants over a season with and without this insect. This will provide an empirical estimate of the agricultural impact of this pest on the growth of soybean.
Since its discovery in October 2009 in northeast Georgia Megacopta cribraria, the kudzu bug, a new pest in North America with origins in Asia, has expanded its range from nine Georgia counties to counties in seven states across the southeastern U.S. in less than three years. This insect’s demonstrable ability to adapt across geography and ecology is due to a diverse genetic repertoire: (1) its intrinsic genetics, and (2) the presence of, and interaction with, endosymbiont genes. These endosymbionts are Ishikawaella capsulata (Fukatsu & Hosokawa, 2002) on which it apparently depends for survival and Wolbachia recently reported in North American collections (Jenkins and Eaton 2011). Mitochondrial DNA (mtDNA) collected and analyzed from random M. cribraria samples from across its range in the U.S. has to date indicated only one female line in North America designated GA1. At this stage it is important to know three things: country of origin, genetic diversity and change in genetic diversity over time. The overall purpose of this research therefore is threefold. First is to determine the country of origin. Second is to analyze the spatial and temporal genetic diversity as it disperses across new geographies in North America. Third is to monitor over time changes in maternal and nuclear genetic diversity for insights into population history and adaptive behavior that may be targeted for control.