MiteSim — a simulation model of the Banks grass mite (Acari: Tetranychidae) and the predatory mite, Neoseiulus fallacis (Acari: Phytoseiidae) on maize: model development and validation

A simulation model (MiteSim) of the mite predator/prey system consisting of Banks grass mite (BGM), Oligonychus pratensis (Banks), and the predatory mite (NEO), Neoseiulus fallacis (Garman), was developed and validated. This model included the effects of temperature, humidity and predation and was coupled to a comprehensive plant-microenvironment model (Cupid). Leaf temperatures, stomatal and boundary layer resistances, and canopy air temperature and humidity are calculated by Cupid. A submodel (POPVPD) uses this information from Cupid to calculate leaf surface humidity. Mite developmental rates and fecundity are each calculated as a function of both leaf surface temperature and humidity in MiteSim. NEO consumption rates are calculated as a function of temperature and prey density. The model predicted the predator/prey population dynamics well for a laboratory microcosm. However, MiteSim consistently overestimated the number of spider mites in field situations, especially toward the end of the simulations. These results suggest that substantial mortality factors occur in the field that are not accounted for from laboratory data.