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Wasp release to tackle cassava killer

The Anagyrus Lopezi wasp - a tiny but highly effective cassava mealybug parasitoid native to South America
(Georg Goergen/IITA)

A group of international scientists is unleashing a swarm of wasps to thwart a pest decimating one of Thailand’s largest food exports.

The 17 July ceremonial launch of 250,000 wasps into Khon Kaen, a province in northeastern Thailand, is an attack on the region’s recently-identified cassava mealybug problem.

The bugs, a recognized enemy of cassava crops in South America and Africa from three decades ago, have arrived in Asia.

Scientists confirmed the spread of the cassava mealybug to about 200,000 hectares of farmland in eastern and northeastern Thailand in late 2009, then set their targeted attack on the bugs in motion, said Amporn Winotai, an entomologist with Thailand’s Ministry of Agriculture. She projects the mealybugs will be under control in six months.

Thailand, the third largest producer of cassava globally, accounts for 60 percent of the world’s cassava exports. The starchy root is mostly grown and consumed in tropical and subtropical regions and serves as a primary source of carbohydrates in diets around the world. Also widely known as yucca, the crop can thrive in poor conditions and is drought-resistant.

The infestation is devastating the country’s cassava industry, said Rod Lefroy, a researcher with Center for Tropical Agriculture (CIAT), an organization that facilitated the wasp solution. CIAT estimates cassava generates more than US$1.5 billion annually in Thailand.

“Most of the five million households growing cassava in the Mekong region are smallholder farmers who rely on the crop for their livelihoods,” Lefroy said. “Quite a few farmers lost 100 percent of their crop last year.”

A harmless (to humans) game of cat-and-mouse

The wasps, scientifically known as Anagyrus lopezi, will be released in pairs. The female wasps use the mealybug as a host for laying their eggs; the larvae then feed off the mealybugs, effectively killing the pests.

The wasps are only 2mm in length and locals need not worry about being stung. After careful testing in controlled situations, researchers are confident the wasps will not cause any problems.

While this is the first sign of the cassava mealybug in Asia, the threat is spreading around the region, Lefroy said.

Travel plans for a small set of wasps to reach Cambodia by the end of the rains in October are in the works, he said.

“It’s going to be an international game of cat-and-mouse,” said Tony Bellotti, a CIAT entomologist who has spent 35 years investigating threats to the root. “As the cassava mealybug finds its way to new countries and regions, we can send wasps.”


This article was produced by IRIN News while it was part of the United Nations Office for the Coordination of Humanitarian Affairs. Please send queries on copyright or liability to the UN. For more information:

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