Insect Mortality Caused by Baculovirus: a Model of Second-Order Phase Transitions

Abstract

Baculoviruses, especially prevalent in Lepidoptera, have attracted the most attention as biological insect control agents. Infection with baculoviruses is usually fatal and therefore can affect host population density, especially if virus transmission increases with host density. Lepidoptera larvae show a strong dose-dependent response to pathogens such as baculoviruses, so their response to various pathogen exposures was studied in the present work. Models of virus exposure to insect hosts are usually judged by whether or not they generate cyclical population dynamics of multiple host generations. However, the existing theoretical models based on systems of differential equations are of little use for practical application due to the large number of variables and free parameters. In this regard, the possibility of using a mathematical model for describing the epizootic Malacosoma neustria L. and Lymantria dispar L. under the influence of nuclear polyhedrosis virus is considered. To assess the sensitivity of insects to the effects of baculoviruses, laboratory experiments were carried out on the mortality of caterpillars under various infectious loads. In this paper, we consider the possibility of constructing a model for the lifetime of insects after exposure to baculoviruses as an analogue of a second-order phase transition in physical systems and give estimates of the model parameters for two insect species at different titers of baculoviruses and at different ages of caterpillars. The dependence of the parameters of the proposed model on nuclear polyhedrosis virus strains is shown. The importance of the applied parameters for the organization of forest protection measures is substantiated.