Abstract: proPlant expert is a computer-based consultation system on crop protection. Since many years the concept meets the requirements of farmers and consultants in both Germany and Europe. Meanwhile about one third of the users are from outside Germany. From March till June 2010 users carried out about 60,000 consultations with the proPlant expert online services. Altogether about 310,000 web pages were called. This high degree of utilisation shows that the unbiased and independent services proPlant GmbH offers also abroad together with local partners are appreciated by the users.proPlant expert helps farmers and advisers to reduce the input of plant protection products to a minimum while giving them economic returns as good or even better than high-input routine sprays. The system offers assistance to users in making decisions on a range of major crops and problems: Fungicide and growth regulator application in cereals, insecticide, fungicide and growth regulator application in rapeseed as well as fungicide treatment in potatoes and sugar beet.For crop protection in winter oilseed rape proPlant expert covers cabbage stem flea beetle (Psylliodes chrysocephala) in autumn and rape stem weevil (Ceutorhynchus napi), cabbage stem weevil (Ceutorhynchus pallidactylus), pollen beetle (Meligethes aeneus), cabbage seed weevil (Ceutorhynchus assimilis) and brassica pod midge (Dasineura brassicae) in spring. Regarding fungal diseases and growth regulators proPlant expert includes consultation on Phoma leaf spot (Phoma lingam) and growth regulator use in autumn and on growth regulator use in spring.Meteorological data including a three-day-forecast, provided by meteorological services, build up the base for proPlant expert. The system analyses these weather data regarding immigration conditions, egg-laying periods and larval development of rapeseed pests, the infection probabilities of Phoma leaf spot since crop emergence in autumn and if the weather is suitable for growth regulator application in early spring.The analyses are presented in online warning services including among others daily updated maps about relevant phenological dates of rapeseed pests, e.g. begin of egg deposition of stem weevils or good weather conditions for immigration of pollen beetles into the fields. This places farmers and advisers in a position to assess the current situation in one or several regions. Together with crop data (e.g. variety, growth stage, infestation levels/yellow trap catches) the system is futhermore able to developa field-specific recommendation on the application of a specific chemical, if necessary. By this fewer treatments are generally needed against spring pests than with a threshold-based control strategy.