CHENNAI: Year after year, local bodies across the State deploy men and machinery to remove water hyacinth and desilt lakes, canals and rivers. But, such efforts are only temporary, doing little to eradicate the highly-invasive plant species.
Water hyacinths reproduce primarily through runners or stolons which in turn form daughter plants with seeds of their own. They also reproduce through seeds, which are known to be viable for almost 30 years.
“We drag them to the sides of rivers or canals to ensure a smooth flow of water,” said an official involved in the de-silting process. That, however, is far from enough. When Express visited desilting sites across the city, canal and river banks were found scattered with uprooted hyacinth, which, once the monsoon sets in, would find its way back into the water along with thousands of viable seeds.
As a comprehensive mechanical removal of these plants is futile, other countries that face the menace use herbicides such as glyphosate, which, researchers say, was found to have the least effect on other life forms. But, herbicides are permitted only for use on land in India, and cannot be used directly on water. To address the issue, R M Kathiresan, Head of the department of Agronomy, Annamalai University, has found in his research that a combination of insects and plants inimical to the water hyacinths can suppress the alarming rate of growth that this plant is capable of. “Weevil beetles and ‘Karpuravalli’ leaf powder are a toxic combination for hyacinths. If the Karpuravalli leaf powder is sprayed on the leaves after the beetles weaken the waxy cuticle coating, the hyacinths will die,” he said.
“This, despite being a complicated process, can effectively and comprehensively destroy hyacinth infestation in water bodies without killing other life forms,” he claimed. In addition to hampering flow of water, water hyacinth infestations suck the oxygen out of the water body. This kills other life forms and lowers the quality of water. In effect, water hyacinths are at once the cause and effect of poor water quality.