Colourful snails attack cardamom plants

KOCHI: Snails refuse to leave Kerala undisturbed. After the Giant African snails, it is now the turn of Indrella ampulla, a mollusc variety with attractive colours, endemic to the Western Ghats.

The snails have destroyed a large number of cardamom plants in a standalone plantation at Rajakkad, Idukki. The molluscs were found feeding on the flowers and young berries of cardamom plants, leading to considerable economic loss. They were also found to be nocturnal feeders.

Pesticide and fungicide applications and saline spray proved ineffective in controlling the snail population. They first appeared in the plantation of K.C. Chellappan some two months ago. “The snails destroyed the flowers and young berries of cardamom plants in around 15 acres,” said Mr. Chellappan.

“The infestation was controlled to some extent by engaging six workers for a week for manually collecting the snails from plants. The workers collected around 500 kg of snails. Stray animals could be seen on the plants even after the exercise,” he said.

According to T.V. Sajeev, an entomologist at the Kerala Forest Research Institute, Thrissur, what took place in Rajakkad was a unique case of an endemic animal assuming the status of a pest. The mollusc was never considered a pest before. “But the trail of destruction it has left in the plantation warrants its cataloguing as a pest,” he said.

The infestation has thrown up an exceptional challenge as one has to control the population of a species which is found exclusively in the Western Ghats. “Bio-control methods cannot be recommended as it may lead to the destruction of its natural population outside the plantation,” Dr. Sajeev said.

When pesticides were applied, the snail went back into its shell to guard itself from the chemicals. On application of saline water, the snail was found producing a froth through which it moved, thus nullifying the effect of salinity, he said.

The possibility of controlling the infestation using urea spray was being explored, said K. Parameswaran Nair, a marketing official of an agricultural products company in Idukki. “The saline spray cannot be engaged as it would damage the plants,” he said.

“It would be ideal to continue the manual destruction of the snail. The question of engaging any other control measure can be considered at a stage when there is a flare up of its population,” Dr. Sajeev said.

Source: The Hindu, 29-11-2010