Can drones and spatial analyses be used to improve biological control of the mile-minute weed in landscape?

The mile-a-minute weed, Persicaria perfoliata, is a fast-growing invasive weed widely dispersed in the northeastern and mid-Atlantic United States. Rhinoncomimus latipes (Coleoptera: Curculionidae), the mile-a-minute weevil, is the major biological control agent used against P. perfoliata. Rhinoncomimus latipes shows a strong host preference and survivorship on P. perfoliata over other related Polygonaceae species. The current visit-and-hand release approach limits the control of P. perfoliata in heterogenous landscapes and hard-to-access areas. The aim of this study was to determine the potential of drone technology and spatial distribution pattern of P. perfoliata patches in landscapes to improve the biological control of this invasive weed. We used landscape metrics at the class level to describe the spatial pattern of P. perfoliata patches based on aerial imagery obtained with drones. The boundary of the patches was detected by drone images, taken at ≤15 m above the ground with a resolution of ≥0.35 cm/pixel, and confirmed by a ground truth survey. The digitized patch polygons were converted to raster and input into Fragstats software to calculate landscape metrics. The results showed that P. perfoliata had a high degree of patchiness in landscapes including hard-to-access areas, making the current hand-release method more challenging. This study demonstrated that drones and spatial analyses could be used for precision biological control of P. perfoliata.