The Effect of Sticky Bands on Cankerworm Abundance and Defoliation in Urban Trees

Abstract

Defoliation by insects can reduce tree growth, increase mortality, and increase herbivory of neighboring plants. In North Carolina, U.S., fall cankerworms (Alsophila pometaria) and spring cankerworms (Paleacrita vernata) are important early-season defoliators and have become more common in recent years. Female fall and spring cankerworm adults are wingless and climb tree trunks to mate and deposit egg masses. Therefore, sticky bands made by wrapping paper bands around trees and covering them with Tangle- Foot™ can intercept female moths as they climb, preventing oviposition and reducing subsequent larval abundance and defoliation. The authors hypothesize that sticky bands reduce cankerworm larvae and defoliation in the canopy when compared to unbanded trees. To test this hypothesis, cankerworm abundance and defoliation were measured on willow oaks with zero, one, and two bands. It was found that trees with two bands captured an average of 38.69% more moths than single banded trees. As a consequence, two-band trees had the least larvae in the canopy. It was found that larval abundance, sampled early in the season with trays of soapy water, was correlated with canopy defoliation at the end of the season. However, tree bands did not affect total canopy defoliation. Although many cities use sticky bands as part of cankerworm management, the authors did not find evidence for their efficacy when defoliation is low.