Effects of landscape structure on abundance of cereal leaf beetle Oulema melanopus and its parasitoid, Tetrastichus julis

The abundance and percentage parasitism of cereal leaf beetle was assessed in 35 wheat fields (14 spring wheat and 21 winter wheat fields) in southern Alberta during June 15 to 30, 2014. Fields were located within a wide range of agricultural landscapes ranging from simple to highly complex. Landscapes were characterized based on the percentage of the non-crop area (including pasture, native and cultivated grassland, and riparian vegetation) and percentage of cultivated area in proximity with the wheat fields sampled.  Preliminary results from 13 fields suggest that the parasitoid positively responds to landscape complexity (semi-natural habitat).  Higher proportion of semi-natural habitats in the landscape increased the percentage parasitism by T. julis, whereas, incidence of crop land decreased it. The response of the cereal leaf beetle to the landscape was inconsistent, and was not strongly affected by the area of wheat fields in the landscape. By contrast, the proportion of barley fields in particular, and cropland in general, had positive effects on beetle abundance.

Key words: landscape complexity, Semi-natural habitats, spring wheat, winter wheat