Postdoctoral Associate University of Georgia Tifton, Georgia
The cereal leaf beetle Oulema melanopus L. (CLB, Coleoptera: Chrysomelidae) is an invasive pest attacking multiple cereal crops in North America. A specialist parasitoid, Tetrastichus julis (Hymenoptera: Eulophidae), was introduced from Europe as a classical biological control agent, and there is little knowledge on the impacts of predators on CLB. We assessed the role of landscape complexity on CLB abundance and its parasitism and predation in Alberta, Canada. Predation was assessed using sentinel CLB egg cards in 18 wheat fields (early season), and collecting predators in 26 fields and conducting molecular gut content analysis to detect CLB DNA (late season). In addition, we surveyed CLB abundance and parasitism in 54 fields (late season). Fields were located within a wide range of agricultural landscapes characterized by the percentage of the seminatural habitats and cultivated area in proximity to the fields sampled. CLB abundance decreased with higher crop diversity at the 0.5 km scale and increased with CLB host crops in the current and previous years at multiple scales. Egg predation increased with proportion of wooded areas and non-cereal crops at the 0.5 km scale. Although crop diversity showed a positive association with predator abundance, it showed a negative association with percentage of predators positive for CLB DNA. CLB parasitism increased with CLB abundance and in landscapes with increased canola and alfalfa during a year of low CLB abundance. Our study suggests that habitat management practices that optimize crop diversity and wooded areas have potential to enhance CLB control.
