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Sci Tech
Bio-control agents for managing cotton pest
By Our Agriculture Correspondent
Helicoverpa armigera larva affected by nuclear Polyhedrosis virus.
BIO-CONTROL agents have proven to be effective tools in managing the devastating insect pests of cotton, and these simple and cost-effective biological organisms can be integrated with other environmentally benign strategies to make cotton cultivation more rewarding for the farmers," says Prof. S. Jayaraj, an international expert on Integrated Pest Management, who is now with the Entomology Research Institute, Loyola College, Chennai. Helicoverpa armigera, the cotton bollworm is the most dreaded among the pests, and it can be economically and effectively managed.
It can be done by using a host of bio-control agents and other eco-friendly approaches, according to Prof. Jayaraj. "Nuclear polyhedrosis virus (NPV) is one of the bio-control agents that works with stunning effect in managing the boll worms.
The viral suspension at 500 larval equivalent per hectare should be sprayed on the crop in the seventh and twelfth week after sowing. The sprayings should be taken up only in the evening hours," he explains.
The larval suspension should be mixed with ten per cent cottonseed kernel extract, ten per cent crude sugar solution and 0.1 per cent each of Tinopal and Teepol.
Then the whole mixture is to be diluted just enough to meet the needs of ultra-low volume spray. "This combination can ensure an effective control of Helicoverpa larvae. There are simple and standardized techniques for producing NPV at local levels, which can be taken up well-trained rural educated youths," explains Prof. Jayaraj.In addition to the spraying with NPV, cotton farmers should also strive to conserve the population of natural predators and parasites in the eco-system.
Inundative release of egg parasite, Trichogramma sp at 6.25 cubic centimeter per hectare at 15 days interval three times from the 45th day of sowing will prove beneficial.
The egg-larval parasite, Chilonus blacksbumii and the predator Chrysoperla should be released at the rate of 1,00,000 per hectare in the 13th and 14th week after sowing for effective management of the pest.
The biological control measures can be made to work more effectively by integrating them ideally with cultural practices as well. Synchronized sowing of cotton preferably with short duration varieties in each cotton ecosystem is one important aspect.
Care should be taken to avoid continuous cropping of cotton during winter and summer seasons in the same area as well as ratooning.
Mono cropping should be avoided.
Inter-cropping and border cropping with less preferred crops such as greengram, blackgram, soyabean, castor and sorghum will help reduce the pest infestation. Removal and destruction of affected bolls, and other crop residues can help in avoiding the carry over of the pest to the next season. "
Above all a sound crop nutrition and judicious water management to prevent excessive vegetative growth should be adopted for the successful implementation of integrated pest management strategies," points out Prof. Jayaraj.
The eco-friendly "green cotton" production technologies will go a long way in protecting the interests of the growers as well as the health of the environment, according to him.
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