Putting off pests
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CTA. 1997. Putting off pests. Spore 72. CTA, Wageningen, The Netherlands.
Permanent link to this item: http://hdl.handle.net/10568/48916
Internet URL: http://spore.cta.int/images/stories/pdf/old/spore72.pdf
Stemborers can cause immense damage to maize and sorghum: in some cases losses as high as 80% have been recorded, especially with one particularly damaging species, Chilo partellus. Stemborers are difficult to control by chemical means because of...
Stemborers can cause immense damage to maize and sorghum: in some cases losses as high as 80% have been recorded, especially with one particularly damaging species, Chilo partellus. Stemborers are difficult to control by chemical means because of their habit of burrowing inside the plants. Scientists at the Institute for Arable Crops Research (IACR-Rothamsted), UK, the International Centre for Insect Physiology and Ecology (ICIPE), Kenya and the Kenyan Agricultural Research Institute (KARI), have made some interesting discoveries during their search for an effective means of biological control to the stemborer problem. Together, these organizations started by selecting grasses, which are more attractive to the stemborers than the cereal crops they attack, to act as 'trap' crops around the perimeter of crop fields. However, they also found that some plants acted as 'repellent' crops and drove the insects away. One of these, molasses grass (Melinis minutiflora), when grown in every third row of crop, proved particularly effective in driving the stemborers away from maize and sorghum and into the trap crops planted around the edge of the field. The molasses grass was found to have the additional benefit of exuding a chemical which attracted parasitic wasps of stemborer, which were deceived into thinking that there were higher numbers of stemborers present in the cereal crop. The wasps proceeded to kill the stemborers that were in the crop before flying on to adjacent fields and attacking the stemborers present there. The trap crops, which were of napier grass or sudan grass planted round the edges of the fields, also had additional benefits. Both grasses are not only good for stabilizing soil but are also good forage crops that can be cut-and-carried for zero-grazed cattle. Napier grass is also able to survive during periods of drought, and can act as a wind-break and prevent wind-lodging, which is common when the stems of maize and sorghum have been damaged by stemborers. ICIPE PO Box 30772 Nairobi KENYA IACR-Rothamsted Harpenden Hertfordshire AL5 2JQ UK