Weed control

Exotic weeds from Central and South America that eat up and smother aquatic habitats in Assam, and how to combat them.

Assam is a blessed land—the rainfall is copious and the mighty Brahmaputra and many of its tributaries flow through the state. The occurrence of countless bheels in the flood plain habitat of these rivers has enabled the land to store water in ponds which have been home to numerous species of native fish since time immemorial. The people of this land, who like to catch as well as eat the protein-rich fish, harvest their fish resources throughout the year. Today, the people even search the mud floors of the water bodies with their hands for fish.


Rural people of Assam fishing in a local bheel

Domestic ducks in a water body, Assam

This happy situation began changing largely with the arrival of two exotic weeds: Ipomoea carnea from Central America and Eichhornia crassipes from Amazon basin, South America. These two species have smothered the aquatic habitats in the government lands (bheels along highways and tanks), destroying their capability to harbour fish, gradually converting the aquatic habitat into a xerophytic one. While E. crassipesis a floating plant which can be easily removed, I. carnea is a deep-rooted plant and is difficult to eradicate. Any remaining stem and seed that is in the soil rapidly re-infest the cleared areas. Therefore repeated clearing of the stems from the soil can help in successfully controlling this weed. India with its enormous human resources could and should control these two weeds. Hugely successful employment generation schemes of the government in rural areas should target restoration of water bodies by eradicating these weeds, that will help the rural poor in meeting their protein requirements, provide economic incentives through increased fish production, and help in water conservation. A water body without these weeds can be extremely valuable for fish production and can be used to maintain ducks as well—another protein source for the people.


A waterbody in Govt land (near the highway) in Assam covered by Eichornia crassipes and Ipomoea carnea

Gopal Deka, Forester Grade I of Jia Gabharu village (Sonitpur West Forest Division), is in charge of a pond that is 1.5 times the size of a basketball court. With the help of the villagers (110 families), he keeps the pond free of weeds. In June 2013, he and his colleagues bought fingerlings worth Rs13,000 from a private agency (sadly, the Fisheries Department in Assam is very inactive), released them in the pond and harvested them in mid-January 2014. Each family was given 2 kg of fish worth Rs400 on the day the fish were harvested; the remainder was sold for Rs75,000 and the money deposited in a bank account to be used for the welfare of the villagers.


The pond maintained by Gopal Deka and the villagers

It is because there are dedicated men like Gopal Deka, who work closely with WWF-India, that the fish-rearing programme has been a success. There is an urgent need to eradicate these two weeds from the aquatic habitats of Assam. This work can be started in the Sonitpur elephant-conflict area as a way of providing additional support to the people who suffer in the cropping season because of marauding elephants. WWF-India’s North Bank Landscape team should do a brief analysis in one of the worst affected villages to find out how much revenue they are losing, and how many wetlands in the village can be restored for revenue generation through aquaculture.

Acknowledgements: Special thanks are recorded to Madhavi Sethupathi (Orient Blackswan, Chennai) for reading through this short article and to Bivash Pandav and Pranav Trivedi for additional points.


This article was first published in the 2014 April edition of Saevus magazine.

About the Author /

Dr A.J.T. Johnsingh is one of India’s foremost field biologists and conservationists. He retired as Dean, Faculty of Wildlife Sciences, at theWildlife Institute of India in 2005. He lives in Bangalore and works for Nature Conservation Foundation as Eminent Wildlife Biologist and for WWF-India as Honorary Scientific Advisor.

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