CRI听力:Organic Pesticides

Ants are highly effective hunters and have a voracious appetite for insect prey. That's why scientists in the southern Indian state of Kerala are using them instead of pesticides to control pests on cashew plantations.

The Kerala state government says chemical pesticides are to blame for scores of human deaths and hundreds of children born with deformities.

The aerial spraying of the chemical pesticide Endosulfan has been used by farmers in Kasargode District for more than 20 years. Endosulfan, which causes nerve damage, is already banned in 80 countries, while others have announced phase-outs over the next few years.

Dr. K. M. Sreekumar of Padannakkad Agriculture University says using natural predators like ants can be a very effective alternative.

"All the bio-control techniques are alternates for pesticides-very good alternatives for the pesticides because they, these ants will be searching for the pest. Because they have to feed, so they will be searching for the pest always, and eat away the pest."

The ants feast on all kinds of bugs, insects and pests. During the university's three-year study, scientists hope the ants will target the tea mosquito, the most destructive pest affecting the cashew crops.

The mosquito sucks the sap from tender shoots of cashew nuts and fruit crops, reducing output by almost 50 percent.

One of the first farmers to use red ants is cashew farmer Nellikal Vasavan.

"My method is simple. I pluck the leaves containing ant colonies and carry them to other trees. Similarly, by tying a long rope from an ant-infested tree to another one, I make use of dried fish to attract ants by the smell."

Vasavan says the cashew trees with colonies of ants are healthier than other trees. By moving the ants to other trees, the natural predators, who also consume mosquito larva, have kept the pest population under control.

While using ants for pest control is cheaper than using pesticides, more eco-friendly and harmless to humans, scientists say it has limitations. There are no techniques for cultivating red ants in large numbers if the method is to be applied on a larger scale.

More importantly, Professor Oommen.V. Oommen, a scientist at the University of Kerala, says there is no established way to control ants during harvest time if their numbers grow significantly.

"So, it can be used as a biological control, and it can be used successfully. The only thing is, when the population of weaver ants grows beyond a certain number, it can be a little bit of a nuisance that the farmers have to put up with, or the farmers have to find or devise how to harvest their crops when the weaver ant colonies are beyond a certain number."

Farmers in other parts of Asia used ants for pest management in ancient times.

Now scientists hope that the red ants, or weaver ants, will help remedy the situation for future generations.

For CRI, I am Li Dong.