Gut instinct

LAST TIME you noticed a grasshopper in your garden munching away the leaves, did you think of the massive damage it causes to agricultural crops across the world? But getting rid of the pest is not an option as it plays a positive role in recycling nutrients by decomposing plant matter.

Feeding habits of herbivorous pests like grasshoppers have always been a matter of concern as well as interest to scientists. Just by the choice of food, they can alter the plant community of a region. Knowledge about their feeding habits can be important for control efforts and restoration of damaged areas. The main problem with the current control methods is the damage done to non-target plant and insect species. ‘Accurately determining the feeding preferences of grasshoppers can help us understand the magnitude of plant damage, and consequently, whether or not control of grasshoppers is needed in a given area,’ says Alina Avanesyan, researcher at
University of Cincinnati, US.

Avanesyan’s process involves dissecting out the insect gut and isolating DNA from the gut tissue. This DNA is a combination of the DNA of the grasshopper and that of the plants it has consumed. The plant DNA is then enriched in this mixture by an inexpensive and routine technique – PCR (polymerase chain reaction).

The DNA?obtained acts?as a ‘bar code’ for individual plants and can accurately mark out the plant?consumed by the insect. The process is simple and takes less than three hours. It can be used for a variety of purposes, for example to determine how long food has been digested and to explore the sequence of multiple plant species consumed and feeding preferences.

Scientists can also use it to compare specific feeding patterns of different grasshopper species and uncover behaviours that might lead to intensive crop damage in certain areas.

Commenting on the study, Hari Chand Sharma, entomologist with the International Crops Research Institute for the Semi-Arid Tropics, Patancheru, Andhra Pradesh, says, ‘The findings will help us understand the diet of a range of different insect species, and this information could be used to design cropping systems and landscapes to minimise pest damage.’

By arrangement with Down to Earth magazine