Biotech Updates

Effects of Fertilization Type on Abundance of Crop Pests Cannot be Oversimplified

November 20, 2009

Organic farming advocates have suggested that plants supplied with organic fertilizers are better defended against insect herbivores than those supplied with synthetic fertilizers. Researchers at the Imperial College London and the University of Reading in the UK led by Joanna Staley investigated the effects of organic and synthetic fertilizers on the abundance of herbivore species on two sets of cabbage plots for two seasons.

The team found that different insect pests showed different preferences. Brassica specialist Brevicoryne brassicae (cabbage aphid) was found to be more abundant on organically fertilized plants. The generalist Myzus persicae (green peach aphid), on the other hand, preferred plants treated with synthetic fertilizer. Glucosinolate concentrations were up to three times greater on plants grown in the organic treatments, while foliar nitrogen was maximized on plants under the higher of the synthetic fertilizer treatments.

The results showed that the effects of fertilization on the crop pest cannot be oversimplified. "The varying response of herbivore species to these strong differences in plant chemistry demonstrates that hypotheses on defense in organically grown crops have over-simplified the response of phytophagous insects," the researchers wrote in the paper published by the Proceedings of the Royal Society B.

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