Bean Plants Call Predator Wasps to Combat Caterpillar Pests

A research team from the University of Washington (UW) has successfully uncovered a unique defence mechanism in common bean plants that allows them to summon a ‘squad’ of predatory wasps to protect themselves from caterpillar attacks. In a study published in the journal Science Advances, scientists identified a receptor protein known as the inceptin receptor (INR) as the key component of this natural alarm system.

The mechanism is activated when caterpillars consume bean leaves. The caterpillar’s digestive process breaks down plant proteins into chemical fragments called inceptin. These fragments then mix with the caterpillar’s saliva and remain on the leaves. The INR protein in the plant recognises these chemical traces as an attack signal, which subsequently triggers the release of chemical gases into the air.

The released chemical gases contain homoterpene compounds, which serve as a navigational guide for predatory wasps of the species Polybia sp. and Mischocyttarus sp. These wasps arrive to hunt the caterpillars feeding on the plant, thereby creating an effective biological pest control system.

Field tests conducted in Oaxaca, Mexico, demonstrated that plants with normal INR proteins are far more resilient compared to mutant plants with damaged INR genes. Plants that failed to release chemical signals were unable to activate either their internal or external immune systems, making them more vulnerable to destruction by armyworm pests.

These findings offer new hope for the sustainable agriculture sector in reducing dependency on chemical pesticides. Utilising this natural defence system, particularly through traditional intercropping methods such as planting beans alongside maize and squash, is expected to protect agricultural ecosystems in a more environmentally friendly manner.