Inadvertently introduced in the northeastern United States in the 1930s, mile-a-minute weed is a highly aggressive invasive plant that is replacing native species in many areas of the Nation. While a biocontrol agent has been identified, finding and reaching dense patches of mile-a-minute weeds has been a problem for land managers. The solution may be drones carrying environmentally friendly pods packed with tiny weevils.

A tiny weevil (Rhinoncomimus latipes) is a specialist biocontrol agent of mile-a-minute weed, a highly invasive annual plant in the United States. Currently this weevil is released by hand where the presence of the weed is readily detected, which is not practical for large infestations and hard-to-reach areas. West Virginia University researchers and a Northern Research Station scientist developed a spatially targeted biocontrol strategy using an unmanned aerial system, or drone, to detect mile-a-minute weed patches and release the weevil. The team determined the detectability of mile-a-minute weed patches by flying a rotary-wing drone at 15 different altitudes and taking aerial images using natural-color and near infrared sensors. A followup ground survey confirmed of the accuracy of aerial images in locating mile-a-minute weed. The team addressed the second problem, weevil delivery, by developing a new insect-release system that uses 3-D printing to create biodegradable polyvinyl alcohol pods. Results showed that mile-a-minute weed patches were readily detectable on the aerial images at an altitude of approximately 25 meters, and more than 98 percent of weevils successfully escaped from the pods within 24 hours after aerial release. Researchers delivered an aerial detection and deployment method that is reliable and environmentally friendly.