Oviposition and feeding on red pine by jack pine budworm at a previously unrecorded scale

The jack pine budworm Choristoneura pinus pinus is a defoliator distributed throughout the range of jack pine Pinus banksiana in North America. Jack pine budworm feeds primarily on jack pine. More than 2400 hectares of defoliation of red pine Pinus resinosa were noted during an outbreak of C. pinus pinus from 2004–2008 in Minnesota and Wisconsin, U.S.A. Defoliation of red pine across thousands of hectares, detectable during aerial surveys, is a significant deviation from historical records. Fifty-six study plots were established across 15 counties of Minnesota and Wisconsin to quantify densities and impacts of jack pine budworm in locations showing defoliation of both red pine and jack pine. Populatsions of jack pine budworm on red pine behaved similarly to those on jack pine, consuming pollen cones and vegetative shoots. The mean number of egg masses per branch and per site was greater on red pine than on jack pine at study sites in Minnesota and Wisconsin, respectively. It is not known what led to the outbreak of jack pine budworm on red pine, nor is it clear whether landscape-scale defoliation of this magnitude represents an isolated incident or a shift in relative host use. Hypotheses regarding the mechanisms behind this alternative host use by jack pine budworm are discussed.