Virus Transmission in Gypsy Moths is not a Simple Mass Action Process

Abstract

We used the nuclear polyhedrosis virus (LdNPV) of the gypsy moth, Lymantria dispar (Lepidoptera: Lymantriidae), to test one of the basic assumptions of most models of disease dynamics, that the rate of horizontal transmission is directly proportional to the product of the densities of healthy larvae and virus. To do this we made measurements of virus transmission, using small—scale experiments in bags on red oak (Quercus rubra) foliage and field data on naturally occurring populations from a previous study. We observed a decline in the transmission constant as the densities of both healthy larvae and pathogen increased, indicating that the rate of disease transmission is not directly proportional to the product of these variables.