Pyrethroid resistance in Finnish pollen beetle (Meligethes aeneus) populations - is it around the corner
2008
Tiilikainen, T.M. | Hokkanen, H.M.T.
The pollen beetle Meligethes aeneus F. is the most important pest of rapeseed [Brassica rapa subsp. oleifera (DC.) Metzg.] in Finland. After over 20 years of intensive rapeseed growing and annual spraying with pyrethroids, the probability of resistance development may be high. Population samples of the pollen beetle from four different regions representing a range of Finnish rapeseed growing practices were collected, and tested for pyrethroid resistance. Region 1 had a history of intensive rapeseed growing for about 30 years, in region 4 no rapeseed had ever been grown (reference region), and regions 2 and 3 represented differing intermediates in growing intensity (proportion of growing area allocated to rapeseed) and growing history. A standard dip test with lambda-cyhalothrin was used in a dilution series with ten different concentrations. Some of the dipped beetles were also weighed. Insecticide susceptibility in the populations collected from region one differed significantly from the others: 60% of those populations survived the standard dose. There was no difference in the median weight of surviving and dead individuals in the most resistant population, while in the most susceptible population the size of individual beetles significantly affected the probability of death by the insecticide treatment.
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