Innovative approach to manage water hyacinth

The aquatic weed, water hyacinth, is ranked among the top ten weeds worldwide and is one of the most successful colonisers in the plant kingdom.

A native of Brazil, the weed has spread to other parts of the world, through initial intentional introductions for its aesthetic values in Africa, Southern Asia and the U.S.

Manual removal is laborious and expensive. Though herbicides are effective, none of them has been registered in India for use on water bodies restricting their application for the management of this weed.

Sponsored research

Research sponsored by Ministry of Water Resources, Government of India, at Annamalai University has shown that herbicides like 2, 4-D, glyphosate and paraquat are effective in controlling the weed.

However, herbicide use in water system impairs the water quality in terms of dissolved oxygen, electrical conductivity etc. Among the herbicides tried, glyphosate was observed to be safer comparatively.

Besides causing mortality of fishes, the water treated with all these herbicides caused histological damages in fish organs like gills, liver, kidney and brain.

However, water treated with these herbicides proved safe for irrigation to crops like rice and cotton. The Department of Agronomy, Annamalai University through a National Agricultural Technology project sponsored by Indian Council of Agricultural Research, brought out an innovative approach of managing the weed with the application of dried leaf powder of a medicinal plant called Coleus amboinius/aromaticus (Karpooravalli or Omavalli in Tamil).

Dried leaf powder of karpooravalli at rate of 20g/l of water makes water hyacinth dead within 5h of treatment and through electrolyte leakage, water hyacinth biomass gets reduced drastically in 3 days.

Large scale cultivation

However, this karpooravalli needs to be cultivated on a large scale to make available the required quantity of leaf powder. Utilising this weed , through composting and incorporation at 6.25 t/ha favoured rice yields.

(Dr. R.M. Kathiresan, Prof and Head, Department of Agronomy, , Annamalai University, Annamalai Nagar, Tamil Nadu, India – 608 002, email: rm.kathiresan@sify.com, mobile: 9655188233.)