Photo by Alexander Wild. http://www.alexanderwild.com

A new study published in the Journal of Economic Entomology shows that the presence of weaver ants on cashew trees is beneficial, as the ants are predators of many insect pests.

“Flushing terminals were significantly less damaged by the mosquito bug, the brown shoot borer, the apple-nut borer, and coreid bugs on trees with weaver ants compared with trees without the ants,” the authors wrote. “The damage caused by each of these pests was significantly lower on trees with weaver ants compared with trees without the ants, showing that the ants were able to keep these pest damages under the control threshold.”

Co-authors Renkang Peng and Keith Christian had previously shown that weaver ants, also known as green ants, could be used in mango orchards as biological control agents. In fact, they found that in some cases the ants were more effective than chemical pesticides.

In the case of cashews, the authors found that weaver ants can be used to control certain insect pests, but they are not effective against branch borers, stem-root borers, or thrips. They also advise growers to avoid useing insecticides such as Cypermethrin, Permethrin, Fenvalerate, Dimethoate, Carbaryl, Trichlorfon, Methidathion, Fenobucarb, and Fipronil because they can kill the beneficial ants.

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– Weaver Ant Role in Cashew Orchards in Vietnam