Identifying weather‐related covariates controlling grape berry moth dynamics *

The use of plant protection products requires precise forecasting of the susceptible larval stages of the grape berry moths Lobesia botrana and Eupoecilia ambiguella as these dynamics vary with the weather pattern of a particular year. The objective of this research has been to partition the relative influence of specific climatic factors on the dynamics of these insects. Data taken from 7 years of continuous monitoring of the flight occurrence of male adults, and of the following development stages (i.e. eggs and larvae), was analysed by a generalized Leslie process. The model type reduces the population to three probabilities: development, survival and fertility. Each probability can be modelled as a function of the associated weather factors, while the functional relationships and the model parameters are established. The analysis started with the simplest approach and, in a step‐by‐step procedure, model complexity was added until a sufficient fit to the overall data set was achieved. Within the magnitude of the model, development rates were controlled solely by temperature, but the duration of single stages (i.e. survival) was found to be affected by a combination of temperature and relative humidity. The model represents a combination of mechanisms within a season with empirical components.