Oilseed rape crops are an important in southern Sweden because of the high intensity of wheat growing. Pollen beetles are the most important pest in oilseed rape and causes often economic losses. Therefore it?s of great importance that we can control the population density, e g by using insecticides if necessary, to avoid mayor yield losses. In year 2000 pollen beetles were numerous in the province of Östergötland. The farmers sprayed with insecticides several times, but with low effects on the beetles. Field trials and laboratory experiments showed that pollen beetles had developed resistance against pyrethroids.