Abstract: The grape berry moth and European grapevine moth are the key pests of viticulture inEurope. The control commonly relies on insecticide treatments, at least outside of areas, wheremating disruption is applied. Using the simulation model “Twickler” the effectiveness ofinsecticide treatments should be enhanced by combining data from weather stations with datafrom population dynamics of earlier years that end up in forecasts concerning importantbiological stages of the grape moths. The “Twickler” model was tested using datasets ofpopulation dynamics from several Franconian vineyards (Germany). The model simulates thepopulation development of E. ambiguella and L. botrana and predicts the start of flightoccurrence, beginning of oviposition and first larvae-hatching. These modelled informationcoincided well with corresponding data monitored in the vineyards. Twickler predicts thebeginning of egg deposition and larvae hatching earlier than found in reality, indicating somedeviance with respect to the underlying biology of the moths. Nevertheless it is seen as anadvantage especially for extension services, since there would be enough time to releasewarnings to vine-farmers. This enables the farmer to apply insecticides at the right time andachieve a maximum efficacy and thus protect natural resources. Yet there are some technicalproblems that need to be solved, hence further investigations are suggested to confirm theseresults.