Conservation biological control of Colorado potato beetles in the eastern United States

In order to improve conservation biological control efforts, it is key to measure the ecosystem services that natural enemies provide in prey suppression. Such knowledge may then be used to evaluate the impact of individual predator species and subsequently manipulate the habitat to improve the efficacy and abundance of the most important predators in an assemblage. In this study we manipulated the habitat in an agroecosystem and measured the impact on predator-prey interactions. We collected foliar predators from field plots with different mulch treatments and assayed them for DNA of the target prey, Leptinotarsa decemlineata (Say), using species specific primers. Predator species abundance and diversity were not influenced by habitat manipulation, while prey density was highest in plots without mulch. Gut-content analysis revealed that the highest incidence of predators positive for L. decemlineata DNA was in plots without mulch, where target prey abundance was highest. Therefore, the lower prey abundance in mulched plots did not seem to be due to predation. The most abundant species in the predator assemblage was Coleomegilla maculata, which had the lowest proportion of L. decemlineata in the gut. Podisus maculiventris, Perillus bioculatus, and Lebia grandis were less abundant but had a higher incidence of target prey DNA in the gut. DNA detectability half-lives were used to adjust for inter-specific variation in DNA digestive rates for four predator species. Using this information to adjust actual number of positives for prey DNA, we compared proportions positive for L. decemlienata and found that P. maculiventris is the most effective predator species in the complex.