Multiannual infestation patterns of grapevine canopy inhabiting Scaphoideus titanus Ball leafhoppers


Abstract: This paper summarizes the procedures for designing, parametrizing and validating amodel representing five years infestation patterns of Scaphoideus titanus populations ingrapevine plant canopies, on the basis of temperature influences. The development of S. titanuscomprises nymphs, adults, diapausing eggs and post diapausing eggs. The basic elements of themodel are temperature-dependent i) stochastic development of the four “life stages”, ii)developmental and senescence rates, and stage-specific survivorships, and iii) reproduction. Thephenology model is based on a time-varying delay with attrition and operates on a time steplength of 1 hour. It is initialized by proportional entries of hatching eggs resulting from a Weibullfrequency distribution. Temperature effects on the survivorship of non-diapausing life stages aremodelled via attrition and on fecundity rates via input into the diapausing egg stage. Diapausingeggs, however, do not suffer from adverse temperature conditions. If the temperature is between0°C and the lower developmental threshold all life stages except the diapausing eggs suffer froman additional temperature dependent mortality. The model is validated with observations madeduring five years in a Southern Switzerland (located at Contone) vineyard. The model predictionsare in agreement with the observations. The successfully validated model will be inserted into anAdaptive Management system aiming at rationalizing pest management and learning how thepest population system works.

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