Magazine article Science News

Fighting Bugs to Save Cassava

Magazine article Science News

Fighting Bugs to Save Cassava

Article excerpt

"The enemy of my enemy is my friend."

South American farmers are making this Arab proverg a strategy in their fight against insect pests ravaging their cassava crops. Mustering an arsenal of natural enemies, farmers are deploying predatory wasps, a lethal virus, and cannibalistic mites against cassava pests, says Anthony Bellotti, an entomologist at the International Center for Tropical Agriculture in Cali, Colombia (CIAT). The starchy roots of the cassava plant feed 500 million people in South America, Africa, and Asia.

Initial results of an ongoing, four-year field project in southern Brazil and Colombia have shown the potential of biological pest control to reduce the amount of chemical insecticides used and to increase yields at the same time, Bellotti announced at a press conference held last week in Washingtonmm, D.C. The briefing was arranged by the Consultative Group on International Agricultural Research, an intergovernmental umbrella organization for 18 agricultural research centers around the world, including CIAT.

Cassava plants are under constant attack from the cassava hornworm and the green spider mite. Both insects defoliate thousands of hectares of cassava fields, killing the plants and reducing yields.

The hornworm "is a voracious feeding machine" that grows up to 5 inches long. "One hornworm consumes about 1,100 square centimeters of cassava leaves" before spinning its cocoon and later hatching as an adult moth, states Bellotti.

Farmers are fighting the hornworms with a predatory wasp that stings and paralyzes the caterpillar, then chops it up and carries the slices home to feed its young. …

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