A dynamic model for the development of the European red mite Panonychus ulmi (Koch) populations is presented and validated with four independent field data sets. It has the following characteristics:
1. Mite development, survival and reproduction are mainly driven by the daily temperature extremes and precipitation, modified by the food supply and nitrogen status of the host.
2. The population cohorts pass through egg, juvenile and adult life stages. Their development and aging occur above the stagespecific temperature thresholds and are modelled with the distributed delay method to account for the observed variance around the mean transit (development) time.
3. The link between the grapevine (Vitis vinifera L.) host plant and the European red mite population is modelled via the metabolic pool approach. The bitrophic relationship between the host and the herbivore has a quantitative and a qualitative component: the plant supplies food (dry matter) to the feeding mite stages, which conversely reduce the photosynthetically active leaf area. The qualitative aspect concerns the effect of the nitrogen concentration of the vine leaves on oviposition and development of the spider mites. The energy flow within and between trophic levels is expressed in dry mass equivalents [g].
4. The negative impact of rainfall is a significant component of the model. Precipitation affects oviposition and survival of the mites.
For the validation with four data sets all parameter values were kept constant except for fecundity which presumably varies among mite strains in different vineyards. The model successfully simulated the mite dynamics of different locations and years.