Diversionary tactics save crops from pests in developing countries‏

Research published today (8 January) by scientists funded by theBiotechnology and Biological Sciences Research Council (BBSRC) reveals theeffectiveness of using 'push-pull' agricultural techniques in developingcountries to save crops from insect damage. Scientists at BBSRC-sponsoredRothamsted Research, working with researchers principally from icipe inKenya, have found that the approach produces real and tangible benefits forsubsistence farmers and, if adopted widely in African countries, could havea huge impact in reducing crops lost to pest infestation. The researchersalso show that the 'push-pull' approach has intriguing potential forreducing animal infections, and potentially even to control human disease.

'Push-pull' entails mixing, into a field of crops, plants that repel insectpests (the 'push') and planting, around a crop, diversionary trap plantsthat attract the pests (the 'pull'). In the Rothamsted studies, the 'push'plant, desmodium, was also found to give extremely effective control of theparasitic African Witchweed.

The research paper, published online in a special edition of the journalPhilosophical Transactions of the Royal Society B, shows that using the'push-pull' approach to manage pest problems offers real benefits in areaswhere economic and ecological factors provide disincentives to employpesticides and fertilizers. In areas of Kenya, Tanzania and Uganda where theapproach has been adopted, the profit a farmer can produce per hectare hasincreased by between three and four times the amount generated by standardpractices. Currently, around 10,000 subsistence households in East Africahave adopted the approach, but the potential impact if the practice were tospread more widely is enormous.

'Push-pull' farming harnesses the power of semiochemicals (behaviourcontrolling chemicals). Scientists can exploit the properties of certainplants releasing semiochemicals that either attract or repel devastatinginsect pests. Up until now, the 'push' and 'pull' plants have been harvestedand used as cattle feed, but new research in Kenya has shown thattraditional food crops, such as beans, can be planted amongst the 'push'plants to provide additional food for the farmer's family.

Professor John Pickett, a leading researcher at Rothamsted Research on'push-pull' approaches, said: "For the first time, we have been able to showthe real and tangible benefits that using push-pull farming brings tosubsistence communities in Africa. Many farmers in developing countries donot have the resources or predictable rainfall needed to invest infertilizers and pesticides. By exploiting 'push' and 'pull' crops, ourresearch has shown that communities can significantly increase the benefitvalue of the crop their land can produce. At the moment, an impressivenumber of East African farmers have adopted the technique, but the overallproportion is still small. If more subsistence farmers used 'push-pull'approaches, there could be massive improvements in the amount of food theycould grow.

"Western farmers could also benefit from adopting the practice. Most areasof farming are under pressure to reduce the amount of pesticide they use andplanting complimentary 'push-pull' crops could be an effective way of doingthis."

Professor Nigel Brown, BBSRC Director of Science and Technology, commented:"This project is an excellent example of the benefits of applying BBSRCscience to issues facing farmers in the developing world."

There are also other potential uses for 'push-pull' approaches. TheRothamsted scientists and other international groups are developingtechniques that could help control further pests and diseases. Prof Pickettexplains: "New studies have shown that the principles of 'pushing' an insectaway from its target and 'pulling' it towards a diversion works effectivelyto control insect-spread cattle diseases and sleeping sickness, a humandisease spread by the tsetse fly."

The Rothamsted Research group, together with their colleagues at icipe,Kenya, will soon begin work on new BBSRC-funded research aimed at harnessingthe weed-controlling properties of the 'push' plant, but in a less labourintensive way.