New pests threaten Sunderban mangrove vegetation

  • Joydeep Thakur, Hindustan Times, Kolkata
  • Updated: Aug 18, 2016 11:23 IST
Amata Passalis damages cow pea, mulberry, tumeric, fenugreek. (HT Photo)

The Royal Bengal Tiger’s habitat in the Sunderbans has come under a new threat. Insects that once used to invade agricultural lands and inflict heavy losses on farmers are now targeting mangroves in the world’s largest mangrove delta.

Scientists have identified at least 45 species of moth in the Sunderbans, at least 25 out of which are recognised as pests that attack different crops including vegetables, tea and cotton among others. Around 16 of these insects have been found in the Sunderbans for the first time.

The Sunderbans – a UNESCO World Heritage Site - located in the extreme south of West Bengal acts as a sponge against cyclones and storms that originate in the Bay of Bengal. It is regarded as the saviour of Kolkata as without these mangroves the city will have to bear the brunt of the storms. It is also home to the only mangrove tiger in the world.

Any threat on the mangrove vegetation would not only make Kolkata vulnerable but also pose a threat to the National animal – the tiger.

Spodoptera Litura damages tobacco, fenugreek, vegetables, tumeric, cotton, groundnut. (HT Photo)

“Some of these insects that are recognised as pests for crops have been found in the Sunderbans for the first time. Scientists are yet to find out whether they have already become mangrove-pests, or are yet to multiply to the extent when they could inflict economic loss. But the signs are alarming,” said Balaram Panja additional divisional forest officer of South 24 Parganas – the district that houses a major portion of the Sunderbans.

The discovery of these pests was made by a four-member team comprising scientists from the Zoological Survey of India and other academic institutions. It was led by Bulganin Mitra, senior scientist with the ZSI. The study was carried out between 2014 and 2016 and was recently published Journal of Entomology and Zoology Studies.

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Some of these insects such as the Oriental Leaf Worm Moth (Spodoptera litura) are considered as notorious pests as they attack a variety of plants including tobacco, cotton, a wide range of vegetables.

“The news is worrisome because controlling a pest in a small agricultural farmland using pesticides and insecticides is a different issue and tackling them in a mangrove sprawling over two countries and over thousands of square kilometers is an altogether ball game,” said Panja.

Experts also pointed out that moths comprise just a small portion of the insect world. There could be thousands of such insects and other animals which could be potential threats to the Sunderbans. There could be beetles, aphids, wasps among others which we still don’t know. Also the team of scientists had restricted their study mostly in the forest fringes. The core area is yet to be examined.

“There could be a host of reasons. Random use of pesticides in agriculture, global warming and climate change and humans coming in close contact with forests could force these insects spread out to newer areas,” said Pranabesh Sanyal former principal chief conservator of the state forest department.

A few years ago experts from a city-based NGO Nature Environment and Wildlife Society stumbled upon two species of beetles that had attacked some trees in the Sunderbans.

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