Striking back at Striga
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CTA. 1995. Striking back at Striga. Spore 60. CTA, Wageningen, The Netherlands.
Permanent link to this item: http://hdl.handle.net/10568/47195
Africa has 75 million hectares of land that can grow cereals, but two-thirds of it is now infested with Striga hermonthica. Other species of striga parasitise leguminous crops like cowpeas. Striga can cause crop losses as high as 85%. To turn the...
Africa has 75 million hectares of land that can grow cereals, but two-thirds of it is now infested with Striga hermonthica. Other species of striga parasitise leguminous crops like cowpeas. Striga can cause crop losses as high as 85%. To turn the tide against this serious pest, scientists at the International Institute of Tropical Agriculture (IITA), in Nigeria, at other research centres in Africa and at advanced laboratories overseas are collaborating in an integrated approach. A study will be conducted and assessment made of varieties of crop that are tolerant to striga; fungal or bacterial seed dressings that will destroy striga seedlings; cultural techniques such as crop rotations using 'trap' crops; removal of striga plants before they seed; the use of crop seeds that do not carry striga seeds and of transplants rather than seed. At IITA researchers are looking for resistance in sorghum and maize. Good levels of resistance are already available in sorghum, whilst in maize a wild relative, Zea diploperennis, is showing good tolerance. This is being crossed with modern cultivars of maize in the hope that the resistance will be transferred. Some promising crosses are being studied. Biological control agents, fungi and bacteria have been isolated but scientists need to make certain that they are specific to striga. As farmers cannot afford spraying equipment, researchers want to develop easy ways to apply the pathogens. These might included seed dressings or covering fields with crop mulches. Striga seed is so small that it looks like dust and is difficult for farmers to see. It can attach itself to crop seeds, so that when farmers save seed from an infected field they could contaminate a clean field in the next season. Emphasis on the use of clean seed will be part of the integrated package, as will techniques to try to stop any striga plants from reaching the seeding stage. Transplanting sorghum seedlings into badly infested fields instead of sowing seed helps to reduce parasitism by about two-thirds. One way of preventing striga from seeding is to rotate cereal crops with 'trap' plants. The 'trap' plants are able to stimulate the striga seedlings to germinate but the seedlings cannot attach to the plants, so they wither and die. Cotton, soybeans, dolichos (lablab), bambara groundnuts and various fodder plants are some of the plants that are known to stimulate striga in this way. Some of these trap' plants are leguminous, so their inclusion in a rotation will also improve soil fertility and provide high protein pulses for home consumption. Other plants that can stimulate the parasite are still being sought. 'Crop rotation' says Dr. Daniel Berner of IITA, 'augmented by other control methods, will be the key in long-term control.' International Institute of Tropical Agriculture P M B 5320 Ibadan NIGERIA