Aerial release of Galerucella calmariensis using drone for the biological control of purple loosestrife

Purple loosestrife (Lythrum salicaria) is an invasive plant to the United States which outcompetes native wetland plants. Galerucella spp. (Coleoptera: Chrysomelidae) are widely used for augmentative biological control of purple loosestrife. However, the release of Galerucella beetles is challenging in hard-to-access areas where many purple loosestrife patches are found. The objective of this study was to test the possibility of aerial releases of G. calmariensis using drones. G. calmariensis adults were loaded to a releasing container (a.k.a. bug pod) which was then dropped from the drone at two flight heights: 15 m and 30 m above the ground. After the aerial release, the beetle were checked for the damage on their body parts, and a comparative laboratory study was conducted to evaluate their feeding ability and mortality for seven days (i.e., two aerial-release groups). The mortality and feeding ability was compared with those of the control group (i.e., beetles that were not released aerially). No significant difference (P > 0.05) was found in the body damage among the three groups. In addition, no significant (P > 0.05) difference was found in survivorships and feeding ability of G. calmariensis among the three groups. This study demonstrated that drones could be used for the aerial release of G. calmariensis for the biological control of purple loosestrife, specifically for spatially targeted releases in hard-to-access areas.