INTERVIEW-Harness "natural enemies" to fight pests and protect crops - World Food Prize winner

by Alex Whiting | @AlexWhi | Thomson Reuters Foundation
Tuesday, 17 October 2017 15:12 GMT

A crop-eating armyworm is seen on a sorghum plant at a farm in Settlers, northern province of Limpopo, February 8,2017. REUTERS/Siphiwe Sibeko

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Researchers have trebled production of maize and sorghum without pesticides, herbicides or fertilisers

By Alex Whiting

ROME, Oct 17 (Thomson Reuters Foundation) - African farmers can lose up to half their harvest to pests, so storing their crops in chemically-treated storage sacks and metal silos can do a lot to boost a farmer's income, agriculture experts say.

Although these are important, the most effective way of protecting the harvest is to stop crops from being infested in the field - without using pesticides, says World Food Prize laureate Hans Herren.

"The way post harvest loss is being dealt with now is a very short term view," said Herren, who co-chaired a major World Bank and United Nations assessment of the state of agriculture involving more than 400 scientists, published in 2008.

"(If) what you put in your bags and silos has less infestation – maybe even none" then it doesn't need to be treated with insecticides, he said.

According to the U.N. Food and Agriculture Organization (FAO), post-harvest food losses in sub-Saharan Africa total $4 billion a year - enough to feed at least 48 million people.

About 20 percent of cereal harvests, 40 to 50 percent of tubers, fruits and vegetables, 27 percent of oilseeds, meat and milk, and 33 percent of fish, are lost, FAO says.

Pests quickly develop resistance to insecticides, and need increasingly powerful - and toxic - chemicals to kill them, Herren said. "So we get into this treadmill which has no end to it. That's not the way to do it."

Herren, a Swiss entomologist and farmer, and his research team have experimented with different farming methods and found they could treble the production of maize or sorghum without pesticides, herbicides or fertilisers.

The method has been tested in Malawi, Kenya, Zambia and Tanzania.

They plant the main crop with a legume, a plant which is rich in nitrogen that feeds the soil. The legume keeps away weeds, attracts insects which destroy pests, and can eventually be used to feed cattle or chickens.

Wild grasses are planted around the edge of the field, which attract pests like stem borers before they reach the maize or sorghum. After the insects have laid their eggs in the grass, it can be used to feed cattle.

"You slowly deplete the environment of pest insects, and natural enemies usually get the ones who get through the barriers and end up on the maize," he told the Thomson Reuters Foundation.

Herren also found that pests were more likely to attack new varieties of maize and sorghum than traditional ones, which have evolved mechanisms to protect themselves.

One such mechanism kicks in when an insect bites a plant, at which point the plant releases a chemical that attracts predators that kill the attacking insect, he said.

"All plants have evolved some system (of defence), you just have to look for it," Herren said.

The fields are also better able to cope with floods and drought, he said. "In drought, all our fields were green and all the (surrounding fields) were brown. It's striking," he said.

Herren won the World Food Prize in 1995 for developing a chemical-free biological control for cassava mealybug that was threatening crops in Africa, averting a potential famine.

He said a new integrated form of farming was needed to curb planet-warming greenhouse gas emissions produced by conventional farming. Agriculture contributes about 24 percent of global emissions, a figure rising every year, according to FAO.

"I don't see how we can survive unless we change this ... Time is running away. Just look around, we can see it," he said.

(Reporting by Alex Whiting @Alexwhi, Editing by Ros Russell.; Please credit the Thomson Reuters Foundation, the charitable arm of Thomson Reuters, that covers humanitarian news, climate change, resilience, women's rights, trafficking and property rights. Visit

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