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Thailand using wasps to combat cassava predator

Thailand using wasps to combat cassava predator

Agricultural scientists unleashed insect against insect Saturday in a bid to save northeast Thailand's cassava plants from an infestation that could cut harvest from the billion dollar industry in half.
The team released 10,000 wasps in Khon Kaen province to prey on mealybugs, said Rod Lefroy, a researcher for the Consultative Group on International Agricultural Research. If the trial goes well, another 250,000 eventually will be set loose.
Cultivated by 5 million Southeast Asian farmers, cassava is used in biofuel and livestock feed, and its starch is extracted for use in food. Thai exports of the crop account for more than 60 percent of global totals and generate about $1.5 billion for local farmers annually, the group and its research partners said.
The crop, originally brought from South America by Portuguese traders centuries ago, thrived before the mealybug infestation, which has spread to 200,000 hectares (494,000 acres) in Thailand's north and northeast and could cut yields by up to 50 percent, leading to millions in lost revenue, they wrote in a statement.
The mealybug, Phenacoccus manihoti, sucks the sap of cassava until it is dry and shrivels up.
CGIAR, whose regional headquarters is in neighboring Laos, initiated the Anagyurs lopezi wasp project after Thai farmers noticed bugs clinging to withered cassava plants in large numbers last year, when crop production decreased by 20 percent to 30 percent, Lefroy said.
"Although they are very small, they tend to amass in quite large numbers on the underside of leaves," said Lefroy, who is working with the Colombia-based International Center for Tropical Agriculture, the Benin-based International Institute of Tropical Agriculture and Thailand's Agriculture Ministry.
"They're very white and look like they're covered in a silky fur," he said.
After confirming the identity of the invasive bug, the team in Thailand imported the biocontrol wasps from Benin in Africa, and began a massive breeding and testing program to prepare for Saturday's release. In the 1980s, wasps were successfully used in Africa to eradicate mealybugs preying on cassava.
The female wasps, only 2 millimeters (0.08 inches) long, inject their eggs into the mealybugs and feed on them, gradually reducing their population.
Lefroy said it is increasingly a regional problem and until recently Asia was largely exempt from the mealybug problem.
"We really need to move into a phase where we admit the honeymoon is over," he said.