Correlation of counts of gypsy moths (Lepidoptera: Lymantriidae) in pheromone traps with landscape characteristics

The effect of landscape characteristics (elevation, slope, aspect, and vegetation) on counts of gypsy moths in pheromone traps was studied in a >5 million ha area in Virginia and West Virginia from 1988 to 1994. Habitat effects on population numbers depend on dominant ecological processes in the area: we define K-, r-, and c-effects as differences in carrying capacity, population growth rate, and colonization rate, respectively, that are associated with different landscape characteristics. To differentiate among these effects, we analyzed individually the following three zones at the expanding front of the gypsy moth population: infested (K-effects), transition (r-effects), and uninfested (c-effects), Among landscape characteristics, elevation was most highly correlated with moth counts, Moth counts increased with increasing elevation in the infested and transition zones (K- and r-effects) which may be associated with good habitats at high elevation. However, the highest average moth counts in the uninfested zone were found at low elevation. Possibly this was a c-effect which resulted from a greater colonization rate in the low-elevation areas where human population densities are greater and the probability of inadvertent transfer of egg masses on human Vehicles is increased, The effect of vegetation on moth counts was much less pronounced than the effect of elevation, Moth catches were higher in deciduous and mixed forests than in coniferous forests and nonforested areas. The effect of landscape characteristics on moth captures was stronger in the transition zone than in other zones.