Simulation of Interactions and Management of Parasitoids in a Multiple Host System

Abstract

Parasitoids are always of major concern in integrated pest management (IPM) programs. However, their use as a control option is handicapped by our lack of understanding of their total life support systems. Because of this, pest managers have, in most cases, only been able to work “around” natural enemies in space and time as opposed to explicitly manipulating their numbers. Manipulation or management of parasitoids is difficult particularly for polyphagous species and for those species whose hosts exhibit a large amount of phenotypic variability. The objectives of this study were to determine the potential effects that phenotypic variability and system complexity can have on parasitism and to suggest ways in which these factors could be used in IPM programs using parasitoids. Data were collected from a natural system composed of the eastern tent caterpillar (ETC), fall webworm (FWW), and a parasitoid ( Hyposoter fugitivus fugitivus (Say)) common to both defoliators. Interactions between the ETC, FWW, and H. f. fugitivus were examined using a simulation model describing the population dynamics of each species. The model was validated using field data including: temporal occurrence, larval population maturity, survival patterns, yearly population trends, and trends in parasitization rates. Sensitivity analyses demonstrated how site-specific conditions, regional host crop and non-host crop mixes, and host population variability could be used in the development and implementation of management programs for parasitoids and pests.