Multiannual infestation patterns of grapevine plant canopy inhabiting Scaphoideus titanus Ball leafhoppers

This paper summarizes the procedures for designing, parametrizing and validating a model representing five years infestation patterns of Scaphoideus titanus populations in grapevine plant canopies, on the basis of temperature influences. The development of S. titanus comprises nymphs, adults, diapausing eggs and post diapausing eggs. The basic elements of the model are temperaturedependent i) stochastic development of the four “life stages”, ii) developmental and senescence rates, and stage-specific survivorships, and iii) reproduction. The phenology model is based on a timevarying delay with attrition and operates on a time step length of 1 hour. It is initialized by proportional entries of hatching eggs resulting from a Weibull frequency distribution. Temperature effects on the survivorship of non-diapausing life stages are modelled via attrition and on fecundity rates via input into the diapausing egg stage. Diapausing eggs, however, do not suffer from adverse temperature conditions. If the temperature is between 0°C and the lower developmental threshold all life stages except the diapausing eggs suffer from an additional temperature dependent mortality. The model is validated with observations made during five years in a Southern Switzerland (located at Contone) vineyard. The model predictions are in agreement with the observations. The successfully validated model will be inserted into an Adaptive Management system aiming at rationalizing pest management and learning how the pest population system works