Another possibility is an indirect effect: The insecticide just kills the aphids, after which their enemies leave the field for a lack of prey. Final result: In this scenario, the aphid population can also recover better after their return because the natural enemies are missing.
Greater biodiversity in organic crop fields
In conventional fields that have not been sprayed with insecticides, the pest control through natural enemies seems to work better thanks to the higher biodiversity in these fields. The biodiversity is far greater still in fields under organic management, as reported in PLoS ONE by the Wrzburg scientists.
The researchers found five times as many plant species and 20 times more types of pollinating insects in the 15 organic crop fields included in the study than they did in conventional fields. Furthermore, they detected three times as many natural enemies of aphids and five times fewer aphids in the organic fields than in the conventional fields.
|Contact: Dr. Jochen Krauss|