Bioassay models with natural mortality and random effects

In fitting dose-response models to entomological data it is often necessary to take account of natural mortality and/or overdispersion. The standard approach to handle natural mortality is to use Abbott¿s formula. Standard overdispersion models include beta-binomial models, logistic-normal, and discrete mixtures. Here we consider combining these two aspects with extensions that allow for the modelling of the natural mortality and overdispersion. Two models are developed: one including a random effect in the linear predictor and other including a random effect in the natural mortality. We consider the application of these models to data from an experiment on the use of a virus (PhopGV) for the biological control of worm larvae (Phthorimaea operculella) in potatoes. Using the models with random effects, we obtained a better fit than that provided by the standard model. non-peer-reviewed