Host-Plant Selection Behavior of Ophraella communa, a Biocontrol Agent of the Invasive Common Ragweed Ambrosia artemisiifolia

SIMPLE SUMMARY: Ophraella communa is an effective biocontrol agent against the invasive common ragweed Ambrosia artemisiifolia. However, whether some closely related non-target plants can become alternative host plant species of O. communa in China remains unclear. Although extensive host-plant selection tests have been used to ensure the host specificity of O. communa in other countries, some doubts remain. In this study, we conducted a series of choice experiments in outdoor cages and open fields to determine the preference of O. communa for A. artemisiifolia and three non-target plant species: sunflower (Helianthus annuus), cocklebur (Xanthium sibiricum), and giant ragweed (Ambrosia trifida). The results showed that this beetle poses no threat to the biosafety of H. anunuus or A. trifida and exhibits a robust dispersal capacity to find and feed on A. artemisiifolia. However, in the future, we should be aware that X. sibiricum has the potential to be an alternative host plant for O. communa. ABSTRACT: 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 Ophraella communa, a natural enemy of the alien invasive common ragweed (Ambrosia artemisiifolia), 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 O. communa for A. artemisiifolia and three non-target plant species: sunflower (Helianthus annuus), cocklebur (Xanthium sibiricum), and giant ragweed (Ambrosia trifida). In the outdoor cage experiment, no eggs were found on sunflowers, and O. communa adults rapidly moved from sunflowers to the other three plant species. Instead, adults preferred to lay eggs on A. artemisiifolia, followed by X. sibiricum and A. trifida, although very few eggs were observed on A. trifida. Observing the host-plant selection of O. communa in an open sunflower field, we found that O. communa adults always chose A. artemisiifolia for feeding and egg laying. Although several adults (<0.02 adults/plant) stayed on H. annuus, no feeding or oviposition were observed, and adults quickly transferred to A. artemisiifolia. 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 O. communa adults crossed the barrier formed by H. annuus to feed and oviposit on A. artemisiifolia planted in the periphery, and persisted in patches of different densities. Additionally, only 10% of O. communa adults chose to feed and oviposit on the X. sibiricum barrier. These findings suggest that O. communa poses no threat to the biosafety of H. anunuus and A. trifida and exhibits a robust dispersal capacity to find and feed on A. artemisiifolia. However, X. sibiricum has the potential to be an alternative host plant for O. communa.