Effects of monitoring position and time of day on pollen beetle numbers in crops of oilseed rape

Abstract: This study investigates the relationship between pollen beetle (Meligethes aeneus Fab.) immigration into an oilseed rape field, the position of the monitoring sample and weather conditions. The knowledge generated will compliment other studies that aim to refine monitoring systems for pollen beetle risk assessment. Better monitoring methods will provide farmers with a more targeted approach to applying insecticides. This may result in fewer applications which would have both economic and environmental benefits. The study was carried out in a winter oilseed rape field on Rothamsted Farm (UK) over five days in mid April 2011, towards the end of the immigration phase of pollen beetles into crops. Beetle population monitoring (a 30 m transect walk over which 10 plants were assessed) was completed every hour on each of the four sides of the field.The transect position (side of the field) had a significant effect on the mean number of pollen beetles per plant which varied over time. Although temperature varied over the study period, it did not affect the number of pollen beetles per plant. When the data from transects were clustered into five groups according to the distance from the crop edge, the abundance of pollen beetle depended on the distance from the crop edge. These preliminary data will help to improve recommendations for best monitoring practice but additional replicated studies are needed before firm conclusions may be drawn from this work.