Predicting Gypsy Moth Population Size in Porcupine Mountains Wilderness State Park using a Satellite Disturbance Index

The pattern of gypsy moth defoliation in the Apostle Islands suggests that moths arrived first to the most isolated islands, not those that are nearest the mainland or the most visited by tourists. Gypsy moths are primarily wind-dispersed, so at least some of the moths may have been blown across Lake Superior. The Porcupine Mountains, about 55 km away, are a potential source for these moths. We used a satellite image-based disturbance index to map the extent of defoliation in and around Porcupine Mountains Wilderness State Park. Using these data and moth trap data provided by the Slow the Spread program, we estimated the moth population to include 310 million male moths. While this does not prove definitively that moths were blown across the lake, it does suggest that the Porcupine Mountains are a likely and convenient source for windborne invading moths. Future research, focusing on wind patterns, may provide additional insight