The temporal and spatial ecology of Brassicogethes (Meligethes) aeneus

Pollen beetles (Brassicogethes (Meligethes) aeneus) are a common and pernicious pest of oilseed rape. This study investigated the migration ecology of B. aeneus using suction-trap data from the longest-running terrestrial insect dataset in the world alongside field-collected data from a five-year sampling campaign. In addition, next-generation sequencing techniques and flight-mills were used to investigate the flight behaviour and migratory potential of B. aeneus. Populations have increased in abundance by ~162% in the UK since the 1980s alongside, but not correlated with, an increase in oilseed rape. The abundance of spring migrants in spring is related to the abundance of beetles caught in suction-traps the previous summer, suggesting that it may be possible to forecast the scale of the spring migration into crops. The number of B. aeneus in daily suction-trap samples is influenced by a small range of environmental variables, time of year and the number of beetles trapped in the previous summer. A selection of statistical approaches (GAM, zero-inflated GLM, random forest and an artificial neural network) were used to investigate daily suction-trap samples, however, none were able to predict the eruptive dynamics that quickly lead to very high counts. The spatial ecology of B. aeneus showed a strong positive relationship between suction-trap and field-caught data and suction-trap data showed spatial synchrony of migrating beetles up to ~150 km. However, no spatial synchrony was found in the field-caught data indicating that at the farm scale the beetle may be locally irruptive, and infestations of the crop are difficult to predict. Studies on the dispersal ability of B. aeneus in the UK proved inconclusive, but indicated that there is a single, homogeneous, UK population with a proportion migrating long distances within the UK. In addition, studies on adult B. aeneus emergence in the field and collated life cycle parameters for B. aeneus are presented as appendices. Together, these findings demonstrate the potential to use suction-traps to forecast the timing and abundance of B. aeneus spring migration and provide growers with timely warnings for crop inspections and control.