Host-Plant Selection Behavior of , a Biocontrol Agent of the Invasive Common Ragweed .

Understanding the host-selection behavior of herbivorous insects is important to clarify their efficacy and safety as biocontrol agents. To explore the host-plant selection of the beetle , a natural enemy of the alien invasive common ragweed (), we conducted a series of outdoor choice experiments in cages in 2010 and in open fields in 2010 and 2011 to determine the preference of for and three non-target plant species: sunflower (), cocklebur (), and giant ragweed (). In the outdoor cage experiment, no eggs were found on sunflowers, and adults rapidly moved from sunflowers to the other three plant species. Instead, adults preferred to lay eggs on , followed by and , although very few eggs were observed on . Observing the host-plant selection of in an open sunflower field, we found that adults always chose for feeding and egg laying. Although several adults (<0.02 adults/plant) stayed on , no feeding or oviposition were observed, and adults quickly transferred to . In 2010 and 2011, 3 egg masses (96 eggs) were observed on sunflowers, but they failed to hatch or develop into adults. In addition, some adults crossed the barrier formed by to feed and oviposit on planted in the periphery, and persisted in patches of different densities. Additionally, only 10% of adults chose to feed and oviposit on the barrier. These findings suggest that poses no threat to the biosafety of and and exhibits a robust dispersal capacity to find and feed on . However, has the potential to be an alternative host plant for .