The Use of Multiple Unmanned Aircraft Systems as a Swarm to Release Sterile Mexican Fruit Fly (Diptera: Tephritidae) Into South Texas Citrus Groves.

Mexican fruit fly Anastrepha ludens (Loew) (Diptera: Tephritidae) is a key economic pest of citrus and represents a quarantine issue along the United States and Mexico Border. In order to respond to this threat, the United States Department of Agriculture produces approximately 175 million sterile Mexican fruit fly pupae per week and releases approximately 150 million adult flies per week via conventional fixed wing aircraft. Unmanned aircraft systems (UAS) offer a novel means of releasing sterile insects aerially, can be deployed on short notice in rapid response scenarios, require a small footprint to operate, and offer an alternative means to releasing sterile insects to traditional manned aircraft. UAS, however, are currently limited in two key areas, range and payload capacity. Swarm technology, flying multiple UAS at once, may increase the utility of UAS by distributing payloads and release patterns across multiple UAS. In order to test the viability of swarm technology in the release of sterile insects we conducted multiple mark release recapture experiments over south Texas citrus groves during 2017, 2018, and 2019. The results of this study demonstrate improved release rates from 89.9% (n = 5) of flies released with ca. 0.64% recapture during 2018, to 98.2% (n = 6) released with ca. 0.74% recapture during 2019. These results demonstrate that swarm technology is a viable technique for increasing aerial release capacity and flexibility of sterile insect technique (SIT) programs.