Migration to and dispersal from oilseed rape by the pollen beetle, Meligethes aeneus , in relation to wind direction

1 Host-plant-odour-induced upwind anemotaxis is accepted as the main mechanism by which herbivorous insects find their host plant within an heterogenous environment, but field data supporting this hypothesis are scarce. 2 The flight directions of the pollen beetle Meligethes aeneus to and from a plot of winter oilseed rape and the direction of the wind were recorded concurrently. The beetles were sampled by eight double-sided window traps encircling the plot. Distal sides of the traps, relative to the plot, sampled the beetles as they flew towards the plot, whereas the proximal sides of the traps sampled them as they flew away from the plot. Paired data on daily catch of beetles in distal or proximal traps and the volume of air impacting each trap were compared. 3 Correlations between daily catch of M. aeneus into distal traps and trap wind volume were negative, indicating that flights by both overwintered- and new-generation insects towards the plot were upwind. 4 Correlations between daily catch of M. aeneus into proximal traps and trap wind volume varied with generation. Catch of overwintered-generation M. aeneus was negatively correlated with trap wind volume, indicating that flight was upwind. Proximal trap catch of the new-generation M. aeneus was weakly/modestly positively correlated with trap wind volume, indicating that flights were downwind or crosswind. 5 Understanding the effect of wind direction on flight of Mr. aeneus holds potential for improving the forecasting of their arrival and spatial distribution on the crop for integrated pest management.