by Hinal Karva
Our campus is a beautiful home to many insects, birds, and snakes. Well, it’s also the home for the small family of giant snails. First, I found a snail on the grass and in a short while four more around it. They seemed cute, big and active snails of our gardens, but this is what I learned about them. This particular species is considered by IUCN as one of the 100 world’s worst invasive species. A native of East Africa, Achatina fulica, is considered to be the largest land snail in the world. The snail is hermaphrodite and can lay up to 100-500 eggs at a time.
Such invasive species don’t just affect the ecology and environment but also the economy of the local community. Let’s first discuss the case of snail infestation in Kerala, which was recorded from 1955 and is believed to have entered the state via the trade route. Since then, they are considered a nuisance as they are found close to houses and also competing with other indigenous species of snails. The Kerala forest research institute (KFRI) is been studying this pest for decades. The problem here is that we can’t use any pesticides as it contaminates the water body (hazardous to aquatic life) and also human health. There are also several cases of contracted meningitis through contact with this snail. The KFRI has come up with a solution where they use vegetable waste to attract the snails and then apply a tobacco and copper sulphate mixture to kill the snails. They also started awareness programmes for snail eradication drives and prediction models to make people prepared for the infestation.
The Kodagu district of Karnataka faces a similar problem from the snail, mainly by affecting the agricultural land (coffee estates) through damaging the coffee plants. The Coffee Board of India has been trying different bait traps to kill the snail population. They initially started using methomyl, a broad-spectrum insecticide, but it used to pollute soil and they eventually stopped using it. Now they have come up with a new bait that includes rice bran, jaggery, castor oil and thiodicarb (a less harmful insecticide). The problem of infestation was so bad that they killed about 30 tonnes of snails in 2015, 24 tonnes in 2017 and by 2018 it has reduced to 8 tonnes. They also started paying people from 4 to 8 Rs per kg of dead snails. They burry all the dead snails in a deep pit and apply salt on the top so there are less chances of disease spread.
In today’s fast-moving world, unknowingly we may carry such unwanted organisms from their native places to a foreign land, where they may become a pest. As you can see, just like the efforts for saving any endangered species, eradicating any invasive species also takes a lot of hard work, time and money.
1)Kodagu coffee planters take on giant snail invasion (August 2019) by Arathi Menon, MONGBAY INDIA
2) Giant snails make rapid inroads into India (Jan 2014) by Elizabeth Soumya
3)Rekha Sarma R, Munsi M, Neelavara Ananthram A (2015) Effect of climate change on Invasion Risk of Giant African Snail (Achatina fulica Ferussac,1821: Achatinidae) in India. PLoS ONE10(11): e0143724