A VIRUS that can be used to manageHelicoverpa armigera, the insect whosecaterpillars or larvae have long ravagedcrops, has been developed by entomologists at the Crop Protection Divisionof the International Crops ResearchInstitute for the Semi-Arid Tropics(ICRISAT), Andhra Pradesh.
Helicoverpa has for long causeddamage to chickpea, the most important post-monsoon crop in AndhraPradesh. The farmers feel that this pesthas affected yields.
ICRISAT scientists conducting theexperiment tried four different treatments on plots of high-yielding varietiesof chi@kpea. One plot was treated with aneem-based botanical insecticide, thesecond with nuclear polyhedrosis virus(NPV); a chemical insecticide was triedon the third plot and the fourth was leftwithout any treatment at all. Pheromonetraps were used to monitor pest incidence, and bird perches provided toencourage such predatory birds as thedrongo or'king crow'.
The NPV particles are ingested bylarvae as they voraciously feed onsprayed leaves. Infected larvae becomesluggish, stop feeding, and eventuallydie. They are often found hanging headdownwards from chickpea plants. Thecadavers are full of brown liquid whichcontains the virus particles. If deadlarvae are crushed and mixed withwater, the resulting mixture can be usedas a cheap insecticide. The virus isinactivated by sunlight, so the mulchshould be mixed with stabilisers, andsprayed on to the plants after sunset toensure its-effectiveness.
The experiments showed that spraying with NPV is not only economical,but is also an environmentally sound strategy.