Scientists at the US Agricultural Research Service have discovered a compound that may help to shed light on how plants respond to insect attacks - by analysing the saliva of grasshoppers.

The service worked with scientists from the Center for Medical, Agricultural and Veterinary Entomology (CMAVE), based in Florida, the Virginia Miliary Institute, and Pennsylvania State University to isolate compounds from oral secretion of Schistocerca americana grasshoppers which were fed on corn seedlings.

When plants are eaten by insects, they emit ‘volatile organic compounds’, or VOCs. These vary with the plant, and also with the insect species that is eating it.

The team found a previously unidentified class of compounds, called caeliferins, in the saliva on the grasshoppers, which could provide new biological tools and directions for exploring the physiological ecology of, and interactions between, insects and plants. The compounds may also influence the swarming behaviour of locusts.

The CMAVE scientists study elicitors of VOC releases to find ways to provoke defensive responses in crop plants under attack to help stay healthy and ‘vigorous’. The centre said that it is well known that insect chewing may induce release of plant VOCs that summon natural enemies of the attacking insects. But insects’ oral secretions may also provoke direct plant defences that impair the pests’ performance. l