A Sickening Solution to save cowpeas

i.new IITA. By making cowpea’s most damaging attacker sick with a virus, IITA scientists may be able to help African farmers harvest much more of this vital, protein-rich food.

Larvae of a moth called Maruca vitrata are eating up cowpea crops throughout Africa. They feed on buds, flowers, leaves, and pods—the older ones move the quickest, feeding continuously and severely damaging the plants. If some of the pests can be infected with a virus, they will reproduce less and live shorter lives. Lowering the population of Maruca in cowpea fields would also lower crop losses, which can reach 80%.

IITA researchers are studying one of Maruca’s natural diseases to find out whether it will work as an effective biological control against the most serious constraint on cowpea production in West Africa, where the crop is widely grown and eaten by millions of people.

“What we’re doing is working to reestablish the balance of nature—letting the natural enemies do the work of chemical insecticides,” said IITA insect pathologist, Dr. Andy Cherry.

Farmers who can afford them rely heavily on chemical insecticides to control Maruca. But these chemicals also kill Maruca’s natural enemies—its predators and parasites. Using a biological control instead, farmers could zero in on Maruca, lower the population of this pest in their fields, and avoid the threat of developing pests resistant to chemical insecticides or harming humans.

IITA scientists are now collecting Maruca larvae from fields in West Africa to find out whether the virus is naturally controlling the insect. Once they know how widely the virus occurs in nature, they can look into ways of redistributing it to areas where it’s less prevalent. With more of this virus and consequently fewer Maruca in the fields, Africans rather than larvae can eat more cowpea.

March 2003