The Battle of the Bug

India loses about Rs. 5,000 crores worth of agricultural products every year due to ravages of insects and pests. The loss is about 18 per cent of our total food production, while India's food deficit even during the worst years is around 10 per cent.

India loses about Rs. 5,000 crores worth of agricultural products every year due to ravages of insects and pests. The loss is about 18 per cent of our total food production, while India's food deficit even during the worst years is around 10 per cent. According to WHO estimates, every two acres a farmer cultivates, he grows one to feed insects and pests.

Because of the impending catastrophe, there is keen awareness in research circles now to develop new control methods and improve upon those that are already existing.

Biological control, that is the regulation of plant and animal numbers with the help of natural enemies, is the most potent and widespread pest-control method.

 A number of viruses have been tested for their potential to kill pests. The unit of Invertebrate Virology at Oxford University and Centre for Overseas Pest Research have begun a joint project on a virus which attacks a universal and devastating pest, the army worm moth. Oxford University is also working on viruses which could be useful in controlling pests in sugarcane and pineapple crops. The Unit has identified a virus which attacks the pine saw-fly with 80 per cent success.

The Small Scale Industry Laboratory at Poona has prepared a wettable powder after blending spores and B.thuringiensis toxins. About 150 species of leaf-eating caterpillars of lepidopteron insects infesting cotton, wheat, sugarcane and groundnut crops, are affected by the spray of the powder and die a violent death. Scientists at Bhaba Atomic Research Centre are busy isolating certain viruses and bacteria with high specificity and selectivity to the pest attacking economically important crops like cotton, castor and groundnut.

The successful field trials for the biological control of Lantana weed with the help of a bug, Teleonemia scrupulous, recently won great applause in academic circles. The-Indian Council of Agricultural Research made a cash award of Rs. 15,000 on the single-handed work of C. Lohumi, a primary school teacher of Nainital. The bug saps Lantana leaves and ultimately destroys the entire bush.

Vector Control Research Centre (VCRC), one of the research units under the Indian Council of Medical Research, is now engaged in mass-rearing of a bug that saps blood from mosquito larvae and kills them. VRC scientists have also identified a fungus in paddy fields that also kills the larvae of malaria mosquito. Attempts are being made to grow the fungus on a large scale so that it can help in malaria eradication.

The traditional and the well known predator of the malaria mosquito is a lavivorous fish Gambusia affinis. The eight cm. long fish has a voracious appetite for mosquito larvae. Two-year long experiments conducted with Gambusia showed spectacular results. Immediately after the fish were released in about 3,800 wells and other stagnant waters of Hyderabad city the larvae count dropped and after six months only 18 pupae were found in the water. Another fish, Poecilia reticulata which is commonly known as guppy is also adapted for mosquito control in polluted waters of India, Burma and Thailand.

Chrysanthemum, a popular flowering plant of winter, is used to extract insecticidal pyrethrum. The dried powder of this flower has been used to kill insects since ancient times. It is harmless to mammals and useful against flies, wasps, mosquito and cattle lice. However, pyrethroids break down in sunlight making them impractical for agricultural use. But the new British product NRDC-143 is stable in sunlight for upto five days.

Nicotine extracted from tobacco is also quite effective against insects and pests. Nicotine is usually sold in the form of 40 per cent solution of nicotine sulphate. The stink of the garlic oil can also put an end to house-hold insects, plant pests and mosquitoes. Field trials for mosquito control with garlic oil have been successfully conducted in the Bombay suburbs of Andheri and Chembur by scientists working at the Bhaba Atomic Research Centre.

Sex attractants or pheromones are the glamour tools in pest management programmes. These subsequent affect the mating behavior of insects. Traps with sex ???attractants are used to attract insects which are subsequently destroyed. When sprayed into the air, the attractants draw large amounts of males throwing them into complete confusion and making it almost impossible to identify a female and male. The next generation of insects is thus greatly reduced.

A variation of this method developed from the pioneering work of Dr. E. F. Knipling is to sterilize millions of male insects by gamma radiation and release them into the air. In a generation or two, the insect population is greatly reduced. A great success of the sterilization method has been the campaign against screwworm affecting cattle and sheep, by the release of a large number of male adult flies sterilized by gamma radiation. Since 1939, DDT is being used against insects carrying malaria, typhus and yellow fever. Since then a number of other chemical pesticides have, been synthesized and the market is now flooded with new pesticidal chemicals and their formulations.

Pesticides are quick in action. Swarms of insects can be sprayed and killed in flight, protecting entire crops. Whole cities can be sprayed to control insect-borne diseases. Due to these factors the demand has increased at a rate of 20-25 per cent per year. But it is now well-known that indiscriminate use of chemical pesticides has been chiefly responsible for the deterioration of the environment and caused irrepairable damage to the soil, fish, wildlife and man. Beneficial species are destroyed while new varieties of harmful species have thrived with even greater resistance. About 50 mosquito species are reported to have developed resistance after continuous spray of insecticides.

But in the context of the global shortage of food and the recurrence of diseases, the war against insects and pests has to be intensified. The farmers and public health authorities need to adopt an integrated approach to pest management, utilizing a variety of control technologies in an economically and ecologically sound fashion. An integrated approach must include the use of chemicals that interfere specifically with the biochemical systems of the pest but do not harm the environment; the use of biological control agents and natural products; breeding of pest-resistant crops and the introduction of genetically modified pests into natural populations; adjusting planting time and use of a combination of seeds, each resistant to different pests; and finally improved formulations and application methods of pesticidal chemicals.