New technique to combat cashew tree pest

PUDUKOTTAI, MARCH 3 . The National Pulses Research Centre (NPRC) at Vamban has developed a viable and cost-effective technique to combat the menace of the stem-and-root borer, a pest that attacks the cashew trees.

A team of scientists led by G. Gajendran, Professor of Entomology, has developed the integrated management technique, under a three-year World Bank-sponsored National Agricultural Technology Project (NATP).

This technique could be adopted by cashew growers across the country, Dr. Gajendran told The Hindu .

He said that though many insects such as tea mosquito bug, thrips, blossom webber, leaf caterpillars and hairy caterpillars attacked the cashew tree, the stem-and-root borer posed the most serious threat. One of the major reasons for the low cashew production and productivity was inadequate management of the pest that would kill the tree if infestation was not identified early and curative methods were not followed.

The pest, belonging to the beetle group and having a pair of long antennae, would attack cashew trees that were 10-15 years old, and five to 10 per cent of the trees were damaged every year. The damage was moderate to high on the west coast, and low to moderate in the east coast, he said.

The technique comprised two components: phytosanitation and post-treatment prophylaxis. Under phytosanitation, dead trees or those that showed symptoms of infestation were uprooted. Prior to uprooting the trees, a process that could be easily accomplished during the post-rainy seasons, the pest should be removed by chiselling out the affected areas and hooking out the pest. In trees with initial and moderate stages of infestation, the pest should be removed carefully by chiselling out only the damaged portion without causing excessive damage to the bark.

In the post-treatment prophylaxis step, it was essential to treat the affected trees with initial- and moderate-level of infestation by stem swabbing and drenching with the insecticide, Chlorpyriphos, (10 ml a litre of water) after removing the pest. This technique would also help to maintain the optimum tree stand in the plantations, thus enhancing production.

Dr. Gajendran said the cashew growers normally diagnosed the problem only when it was in an advanced stage, during which any remedial measure would be of no use. Once phytosanitation and post-treatment prophylaxis were done, the chances of re-infestation would be minimal.