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Eco-friendly methods ward off black-headed caterpillar in coconut

By Our Agriculture Correspondent

BLACK-HEADED CATERPILLAR, Opisina arenosella, is a dreaded pest of coconut. The caterpillars of this serious pest feed on the green matter from the lower surface, and remain in galleries made of silken web and frass. The severity of the incidence of this pest can be noticed in summer (February to June), and the affected trees present a burnt-up-look. The pest population begins to decline with the onset of the monsoon.

"Biological suppression of the leaf eating caterpillars is the most effective way to manage this serious menace. The pest can be managed well by the release of parasites such as Elasmus nephantidis, Goniozus nephantidis, Brachymeria nosatoi and Xanthopimpla punctata in the infested coconut groves," says Dr. K. Subaharan, Scientist at the Central Plantation Crops Research Institute (CPCRI), Kasaragod, Kerala.

When the infestation is severe, the affected lower fronds should be cut and burnt. The under surface of the remaining leaves should be drenched thoroughly using a spray fluid of any eco-friendly, botanical insecticides. The natural enemies of the pest should then be released at least three weeks after the spraying, according to Dr. Subaharan.

The scientists at CPCRI have standardised the techniques for the mass culture of the larval and pre-pupal parasitoids. The larval parasitoid, Apanteles taragamae should be released from the 10th to 25th days of the adults' emergence, and a pair of newly emerged male and female should be released. The progeny of the parasitoids will be female biased. The parasitized larvae should be placed near the fresh leaflet before 12 hours for effective action and development.

The other parasitoid, Goniozus nephantidis, should be released between the 10th and 14th days after adult emergence. One or two mated females of 2 to 3 days old should be released. This parasitoid stings and paralyses the third instar of the host larvae, but the laying of eggs occurs from the fourth and later instars, according to the scientist.

The pre-pupal parasitoids, Elasmus nephantidis, should be released on the eleventh day of adult emergence. Two or three mated females (1 to 2 days old) should be released. This parasitoid is highly host specific and stage specific. The other pre-pupal parasitoid, Brachymeria nosatoi, should be released between the 12th and 20th days of adult emergence. A mixture of both female and male parasitoids numbering between 30 and 50 should be released for effective action.

Another of the pre-pupal parasitoid, Xanthopimpla punctata, is found to be effective in checking the population of the black-headed caterpillar. One or two of the mated females (4 to 5 days old) should be released on the 10th to 12th days of adult emergence to get the desired results, according to the scientist.

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