Occurrence of insecticide resistant pollen beetles ( Meligethes aeneus F.) in Danish oilseed rape ( Brassica napus L.) crops

The pollen beetle is the most important pest in Danish oilseed rape crops and it is essential that farmers are able to control this pest, especially in years when the economic damage threshold will be exceeded. About seven years ago, Danish oilseed rape growers began reporting that the pyrethroids seemed to be losing effectiveness towards pollen beetles. In 2001 18 populations collected from winter and spring oilseed rape fields were tested and very high level of insecticide resistance was found. In 2003 100 populations of pollen beetles were tested, using a FAO dip‐test, for resistance to fenitrothion, lambda‐cyhalothrin and tau‐fluvalinate. It can be concluded that many Danish populations of pollen beetles are resistant to the pyrethroid lambda‐cyhalothrin and to a lesser extent to the pyrethroid tau‐fluvalinate. No resistance to the organophosphate fenitrothion was found.