Charting impacts from invasive insects pushed to new limits
Precise mapping of invasive spongy moth defoliation yields rich insight into the effectiveness of costly treatments and the vulnerability of eastern forests.
Non-native invasive insects have beleaguered eastern forests for decades and the spongy moth (Lymantria dispar dispar) has been one of the most troublesome. For half a century, the standard approach to mapping spongy moth defoliation was through costly aerial surveys. In recent years, a collaboration between Southern Research Station scientists and federal and state agencies has demonstrated the utility and effectiveness of remote sensing to help with this effort. In both 2021 and 2022 researchers mapped spongy moth defoliation at 10-meter resolution across several states. Where persistent clouds limited the use of this precise imagery, more frequent (but coarser spatial resolution) products provided reliable information. In Pennsylvania, precise mapping showed where defoliation had not occurred within large defoliation zones, and this showed the effectiveness of costly insecticide spraying programs on state lands. While spraying is not formally reported for private lands, this effort also revealed where some unreported spraying occurred. In addition, state agencies can use detailed maps of where defoliation occurred and its severity to anticipate where to conduct winter egg mass surveys and where to spray next spring more efficiently. Improved documentation of repeat defoliations over years can inform potential cumulative impacts and tree mortality.
