Title: Predicting defoliation by the gypsy moth using egg mass counts and a helper variable

Author: Montgomery, Michael E.

Year: 1991

Publication: In: Gottschalk, Kurt W.; Twery, Mark J.; Smith, Shirley I., eds. Proceedings, U.S. Department of Agriculture interagency gypsy moth research review 1990; East Windsor, CT. Gen. Tech. Rep. NE-146. Radnor, PA: U.S. Department of Agriculture, Forest Service, Northeastern Forest Experiment Station: 144.

Abstract: Traditionally, counts of egg masses have been used to predict defoliation by the gypsy moth. Regardless of the method and precision used to obtain the counts, estimates of egg mass density alone often do not provide satisfactory predictions of defoliation. Although defoliation levels greater than 50% are seldom observed if egg mass densities are less than 600 per hectare (250/acre), data from Melrose Highlands and the Intensive Plot System (IPS), as well as recent data from New Jersey and Pennsylvania, reveal that egg mass densities above this "threshold" result in damaging defoliation in less than 50% of the observations.