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ICARDA
and CIMMYT Harnessing the Power of Partnership in Wheat Improvement |
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An Integrated Approach to Saving Wheat from Sunn Pest
A relative of the common stinkbug, Sunn pest sucks its nourishment from leaves, stems, and grains. A heavy attack can cause stems to break or empty "whiteheads" to form instead of healthy grain. Even if yield losses are low, the enzymes injected by the insect make wheat grain unsuitable for making bread. In a crop that yields 2 tons per hectare, grain quality can be damaged by only two insects per square meter. If only as little as 2% of the grain is affected, a whole consignment of wheat might be rejected from milling grade. Researchers from ICARDA, the University of Vermont, national research programs, and universities are developing a comprehensive integrated pest management (IPM) program that uses parasitoids, fungi, predators, cultural methods, and other strategies to reduce the impact of Sunn pest regionwide.
One control strategy uses fungi that infect Sunn pests, so the first step was to find and isolate the potentially useful pathogen. Researchers concentrated their search for infected Sunn pest specimens under fallen leaves in foothills close to harvested cereal fields where the Sunn pest spends the winter. They collected several hundred strains of fungi in Kazakhstan, Kyrgyzstan, Syria, Turkey, and Uzbekistan (in Syria they were assisted by the University of Aleppo, and in Turkey by the University of Cukorova and the Plant Protection Research Institute of Adana). This effort yielded the world's largest collection of fungi isolated specifically from infected Sunn pest. It was essential, however, to determine whether these microorganisms could really perform the required task --killing the adult Sunn pest. Pathogenicity trials at ICARDA laid all fears to rest. Some of the fungal isolates were so pathogenic that they killed all of the treated insects in less than a week. Researchers learned that the spores of some fungi lodge between the protective plates of the insect, then penetrate and develop within the insect, blocking vital life support systems. The next task is to select isolates likely to be of most use in the wide range of environments present in Central and West Asia. The isolates collected in hot dry conditions may not do so well in cold conditions elsewhere in the region. Isolates deemed useful for wide application will undergo further testing in the laboratory and in the field. If CWANA countries are to meet their food needs in the decades to come, it is important that the present insecticide-based strategies are replaced with multi-dimensional IPM approaches. Apart from being expensive and potentially damaging to the environment and consumers, insecticides can lose their effectiveness unlike the insect-killing fungi. |
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