REGIONAL CORRELATION OF GYPSY-MOTH (LEPIDOPTERA, LYMANTRIIDAE) DEFOLIATION WITH COUNTS OF EGG MASSES, PUPAE, AND MALE MOTHS

Three different gypsy moth, Lymantria dispar (L.), sampling techniques were compared for their spatial correlation with regional defoliation maps. Counts of gypsy moth pupae and egg masses under burlap bands, a nd counts of male moths in pheromone-baited traps were taken in a netw ork of 150 plots distributed irregularly throughout Massachusetts. The se counts were compared with aerial sketch maps of gypsy moth defoliat ion collected during the same period and digitized into cells (2 by 2 km) cells in a geographic information system. The spatial correlation between counts of the three gypsy moth life stages and defoliation was examined using indicator cross-correlograms. A cross-correlogram quan tifies the spatial covariation between two variables by plotting the c ross-correlation for a series of interpoint distances. Cross-correlogr ams indicated that there was substantial correlation between egg mass counts and subsequent defoliation. These correlations extended to 10 c ells (20 km) in some cases. Similar patterns were observed For counts of pupae. In contrast, there was little cross-correlation between defo liation and counts of male months. These results indicate that counts of egg masses (ol pupae) under burlap bands may be the most suitable v ariable to measure for predicting gypsy moth defoliation on a between male moth counts and regional defoliation is discussed.