Farmers who spray insecticides against aphids as a preventative measure only achieve a short-term effect with this method. In the long term, their fields will end up with even more aphids than untreated fields. This has been reported by researchers at the Biocenter of the University of Wrzburg in the scientific journal PLoS One.
What's the status of the biodiversity in differently managed triticale fields? This is what the biologists at the Department of Animal Ecology & Tropical Biology wanted to find out. Triticale is a cross between wheat and rye. The cultivation of this crop is on the rise across the globe, because it delivers good yields even in poor soil conditions.
When comparing conventionally managed crop fields, which were either sprayed with insecticides or were left untreated, Jochen Krauss, Iris Gallenberger and Ingolf Steffan-Dewenter made a discovery, which should catch the attention of every farmer: "According to our results, the preventative application of insecticides against aphids does not produce any advantages even though it consumes a lot of time and money," Jochen Krauss sums up.
The scientists studied five triticale fields that were sprayed with insecticides against aphids, comparing them to ten other fields without any such treatment. "To be sure, the application of the insecticide led to a short-term decrease of the pest density," says Krauss. "After four week's time, however, significantly more aphids could be found in these fields than in insecticide-free fields. This also astonished the farmers who made their fields available for our study."
More aphids as a result of a decrease in natural enemies
The scientists offer two possible explanations for this phenomenon. One possibility is: The insecticides indiscriminately kill off beneficial animals that feed on the aphids, such as ladybugs or the larvae of lacewings and hoverflies. Because their enemies are missing, the aphi
|Contact: Dr. Jochen Krauss|