Aerial Detection of Seed-Bearing Female Ailanthus altissima: A Cost-Effective Method to Map an Invasive Tree in Forested Landscapes

Abstract

We present an aerial mapping method to efficiently and effectively identify seed clusters of the invasive tree, Ailanthus altissima (Mill.) Swingle across deciduous forest landscapes in the eastern United States. We found that the ideal time to conduct aerial digital surveys is early to middle winter, when Ailanthus seed clusters persist and there is no interfering leaf cover. Because of the color, quantity, and seedpod arrangement, female seed-bearing Ailanthus trees are very conspicuous from the air. With use of digital sketchmapping technology from helicopters, seed-bearing Ailanthus trees were mapped at a rate of 2,000–4,000 acres/hour (809–1,618 ha/hour). We estimated mapping costs at approximately $0.40/acre ($1.00/ha). We were able to relocate, within 100–200 ft, 88–95% of the aerially mapped seed-bearing Ailanthus trees using handheld consumer-grade global positioning systems (GPS) units. This provided enough accuracy to locate seed-bearing Ailanthus for single-stem injection herbicide treatments. To apply these methods to map seed-bearing Ailanthus, land management agencies that already use digital mapping technology (equipment and software) for surveys of insect and disease outbreaks will have minimal costs beyond helicopter time.