Pyrethroid resistance of insect pests of oilseed rape in Germany

Abstract: Many insect pests are present in oilseed rape for a long period of time and are therefore exposed to several insecticide applications even though the application is targeted against other pests. Intensive and virtually exclusive use of pyrethroids for pest management in oilseed rape resulted in a selection pressure and finally in resistant insect pest populations. Since 2005, resistance monitoring has been carried out at the Julius Kühn-Institut. More than 1,800 German pollen beetle populations were tested with lambda-cyhalothrin from 2005 to 2017. Also other insect pests of oilseed rape such as cabbage stem flea beetles, different weevil species and the brassica pod midge were tested within the monitoring scheme. The results showed that the percentage of highly resistant pollen beetles increased from 7% in 2005 to 94% in 2017. Etofenprox and tau-fluvalinate still provide some field efficacy but biotest sensitivity is decreasing. Resistance to pyrethroids was also found for the cabbage seed weevil, the cabbage stem flea beetle and the rape winter stem weevil.