Snails fast becoming a threat

Giant African snails are invading agriculture land and homes in several localities of Kerala, posing a serious problem.

A native of East Africa, the land snail (Achatina fulica) is a pest that attacks nearly 500 plant species, including those bearing fruits and vegetables and even rubber and coffee.

Attacks by the species have been reported from Thiruvananthapuram and Kozhikode cities, Konni in Pathanamthitta district and Palakkad. It multiplies in large numbers during the rainy season and destroys vegetables, papaya, banana and other crops. In some parts of Kollam district, it has invaded coconut trees and local people are planning a drive against them. In Konni, people have destroyed thousands of snails through application of common salt.

Many people have reacted to the pest with revulsion as it enters the kitchens and other parts of their homes, especially at night. They even feed on the walls of homes as they require calcium, which is found in concrete and lime, for development of their shells.

They, however, cannot stand heat and sunlight. It is easily killed by spraying of salt or copper sulphate. But control is difficult once it multiplies into large populations under congenial climate.

How the snail arrived in Kerala is a matter of conjecture. It was reportedly introduced in the then Calcutta as back as in 1847. Proliferation of the species has since been reported from Karnataka, Orissa and Bihar. The snail would have reached Kerala years ago, but may have found an environment suitable for its gregarious multiplication only now.

It is possible that the multiplication of the snails is another symptom of serious disturbance to Kerala's environment. Farmers from some parts of the State have reported seeing unfamiliar insects. They say that the insects had arrived from Tamil Nadu with chicken droppings brought for use as fertilizer. It can also be the result of environmental changes that favour their multiplication.

Many molluscs and insects had been destroyed in the past because of intense use of pesticides in farms and paddy fields. It is possible that it also led to decline in numbers of their predators. Thus, devoid of competitors and predators, the African snail could have found an opportunity to multiply. And a worrisome factor is that it is not just the snails that are spreading in Kerala now. The list includes influenza viruses, mosquitoes and mites.