A frog species endemic to the Western Ghats has been identified as cardamom-friendly, killing moths that are known to destroy cardamom’s pseudo-stem, a major menace faced by farmers.
The bush frog, or Raorchestes ponmudi eats up the shoot borer Conogethes punctiferalis that enters through immature panicles and attacks the shoots and stems, thus destroying cardamom plants, often in a large-scale. The bush frog is widely found in the Ponmudi area of the Western Ghats and is familiar to cardamom planters.
Unlike other frog species, the bush frog’s life cycle is entirely different, and water sources are not primarily needed for the growth of its eggs.
Effect of pesticides
A.K. Vijayan, scientist and former head of crop protection, Indian Cardamom Research Institute, told The Hindu on Tuesday that the bush frog is, however, quite absent in cardamom plantations where highly toxic pesticides are sprayed.
An adult moth lays about 20 to 35 eggs on cardamom leaf margins, leaf axils, panicles and racemes. The eggs hatch within five to six days. Emerging larvae bore into tender panicles, unopened leaves or immature capsules. At a later stage, the larvae bore into the shoots and feed on the central core of the pseudo-stem, resulting in decaying. The caterpillars of this insect bore and feed on flower buds, flowers and capsules. The pest attacks are particularly high from June to September, points out Dr. Vijayan.
Studies have found that each larva feeds about 25 to 27 capsules to attain maturity. Its life cycle is completed within 38-45 days. The adult moth is orange/yellow in colour and is 22-24 mm long with a number of black dots on its wings.
The bush frog is also common in the CHR (Cardamom Hill Reserve) areas of Udumbanchola and Peerumade in Idukki district. Farmers in these regions have reported its presence on cardamom plants, where the species are often spotted at night when it comes out for feeding on the moths. However, aggressive pesticide application is a threat to the bush frog, said Dr. Vijayan.
