Budbreak and leaf growth functions for modeling herbivory in some gypsy moth hosts.

Abstract

Functions are reported which predict percent budbreak and average leaf dry weight from elapsed degree-days (threshold = 4.4oC) for 6 important hosts of Lymantria dispar: Quercus alba, Q. rubra, Q. velutina, Fagus grandifolia, Acer rubrum and A. saccharum. Budbreak observations are also summarised for Betula lenta and B. alleghaniensis. Day 105 (Julian date) was the best single date to start counting degree-days to predict percent budbreak for all species, year, and study locations. Simultaneous solution of the red oak leaf growth function and published gypsy moth larval growth and consumption functions predicted that an average larva will consume c1115 mg dry leaf weight, and drop c156 mg. Apparent herbivory attributable to a single larva was calculated as 1381 mg dry weight, where an average mature red oak leaf weighed 448 mg.-Author