Tamil Nadu Agricultural University (TNAU) has been awarded a patent on Nano herbicide by the Controller of Patents, Patent Office, Government of India.

The patent titled ‘Nano Emulsion Based Botanical Herbicide and Preparation Method Thereof’ was the outcome of research work carried out at the Centre for Agricultural Nanotechnology for the development of a novel form of herbicide using naturally-produced allelopathic chemicals derived from Eucalyptus citriodora.

According to the inventors N. Swathika, K. S. Subramanian and S. Marimuthu, eucalyptus plants produce volatile metabolites that inhibit the neighbouring plants in the natural ecosystem. The fallen leaves surrounding the trees release a wide array of terpenoids especially eucalyptol and citronellal. Since these compounds are highly volatile in nature, efforts were undertaken to develop nano-system to encapsulate them in a micelle with a guar gum as a biopolymer.

The product was developed using two-step process involving high pressure homogenisation and ultra sonication. This bio-nano-herbicide has both pre-emergence and post-emergence herbicidal action against a notorious grassy weed Echinochloa crusgalli.

There was a pre-emergence control of weed seeds at 1000 ppm (parts per million) while highest post-emergence toxicity was observed at 1% spray of nano-emulsion, the researchers explained.