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[NAIROBI] A farming technology that uses intercropping to repel insect pests from food crops has been given a new lease of life by a programme to expand its uptake.

The 'push–pull' strategy intercrops cereals with a repellent plant bordered by an attractive trap plant. For example, maize can be intercropped with desmodium, which repels ('pushes') pests such as the maize stem borer away from the crop, and bordered by Napier grass, which lures ('pulls') stem borers so they lay their eggs in the grass instead of the maize.

Napier grass also produces a gummy substance that traps freshly hatched stem borers so only a few survive to adulthood.

Since its development in 1997, the technique has helped nearly 40,000 farmers in East Africa. Maize yields have increased by up to 3.5 tonnes per hectare, bringing 300,000 people out of hunger and poverty, according to the International Centre of Insect Physiology and Ecology.

The centre has now launched a project to disseminate the technique more widely and to find new push and pull plants with drought and temperature tolerance.

The Adaptation and Dissemination of Push–Pull Technology (ADOPT) initiative, launched last month (30 March), will benefit a further 50,000 farmers living in dry areas vulnerable to climate change in Ethiopia, Kenya and Tanzania. ADOPT has received €2.9 million (US$4.2 million) from the European Union.

"Push-pull is a modern conservation agriculture technology that does not require the use of insecticides or pesticides," Zeyaur Khan, the project's principal investigator, told SciDev.Net. "We hope to have about one million households benefiting from the technology by 2020."

Khan and colleagues developed the low-cost technology in collaboration with Rothamsted Research, United Kingdom, and various national programmes in East Africa.

Kenyan farmer Remjus Bwana said the technology has made his farm more productive. "After adopting this technology, I have seen a remarkable improvement," he said.

However, both desmodium and Napier grass struggle in dry conditions.

"We have started doing new research that will enable us get new species of trap and repellent plants that can withstand high temperature and drought conditions in arid and semi-arid areas of Africa. We are collecting desmodium seeds and grasses from different parts of Africa to see which ones are more resilient," said Khan.

But Ken Giller, a plant scientist at Wageningen University, the Netherlands, said that claims about the push–pull system are overstated. "I do not think that they have yet seen sustained adoption — just farmers experimenting with the technology," he told SciDev.Net.

"Climate change in East Africa is indicating a wetter climate, rather than drier," Giller said. He added said that rigorous adoption studies should be carried out before promoting such technologies.