The intensity of the crop rotation had less impact on aphid enemies than the complexity of the landscape. The natural enemies of aphids benefit probably more of environments with fewer annual disturbances where they find alternative food sources.
Researchers at SLU (Dept. of Ecology) and Lund University have investigated how the natural biological control of aphids in barley was affected by the intensity in crop rotation and the form of the landscape.
The researchers noted the most extensive natural biological control of aphids in barley fields in complex landscapes with a high proportion of pastures. This is environments in which the annual disturbances are fewer and where natural enemies of aphids are assumed to have more opportunities to find overwintering sites, alternative prey and plant-based foods such as nectar and pollen. In contrast, the crop rotation intensity had considerably less impact on the biological control of aphids than the landscape complexity.
Crop rotation intensity was estimated from the proportion of ley grown in the area. High proportion of perennial pasture was considered to be linked to more diverse crop rotations and lower intensity due to a smaller proportion of annual crops.