A Lethal Cocktail for the Chickpea Podborer

Dead crushed larvae of the podborer pest, well mixed with water and a stabilizer, yield a lethal cocktail used by Indian farmers to spray their chickpea fields.

A forty percent increase in chickpea yield was achieved by a group of farmers developing this new biological pesticide in collaboration with the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) based near Hyderabad.

The podborer, the caterpillar of the insect Helicoverpa Armigera, used to destroy over half the earlier harvests of chickpea, the most important post-monsoon crop in the Medak district of Andhra Pradesh.

The farmers contacted ICRISAT, a center supported by the Consultative Group on International Agricultural Research (CGIAR), through the Deccan Development Society, a local non-governmental organization. Ten on-farm trials of alternative podborer control methods were conducted by farmers in Kappadu village, together with ICRISAT scientists.

The trials involved a conventional chemical insecticide, a botanical insecticide derived from the domestic neem tree, and the nuclear polyhedrosis virus (NPV), a natural enemy of the podborer. The NPV particles are ingested by larvae as they voraciously feed on the sprayed chickpea leaves.

The dying larvae are full of brown liquid which contains the virus particles and are collected for the cocktail which should be sprayed at sunset because the virus is inactivated by sunlight.

Vitthal R. Bhagwat is leading a team of ICRISAT entomologists that developed an integrated pest management package consisting of an improved chickpea variety, the botanical insecticide, and the NPV cocktail.

"On-farm experiments have clearly shown the efficacy of this approach," says Bhagwat of the new, eco-friendly and low-cost technology readily adopted by the farmers who had been trained to monitor pheromone traps, count the larval population per plant, and determine the right stage to apply the NPV. They learned how to mix the cocktail and decided to apply three sprays at weekly intervals.

"We did not believe when we were told about it but now we can count on this cheap and effective package," says one of the Kappadu farmers, Narasa Reddy. "We observed that friendly birds only visit plots that were not sprayed with chemical or botanical insecticide, but they are intensely active on the plots sprayed with NPV where they feed on dead larvae that they can easily pick off the plants."

Bhagwat says ICRISAT will continue the on-farm research in the next season. More farmers need to be trained to prepare and use their own sprays as part of a user-friendly and environmentally benign technology.

International Crops Research Institute for the Semi-Arid Tropics (ICRISAT)