Assessment of phytotoxic spent broth and spores of Alternaria alternata (LC#508) as a formulation with enhanced mycoherbicidal activity to control lantana camara

Abstract

Enhanced social concern towards the ill effects of synthetic agrochemicals, their residual toxicity and resistance development in the target pests created a necessity of exploration of alternatives. Fungal biocontrol agents have been used as herbicides over two decades and research continues to enhance their efficacy comparable to synthetic herbicides. Combinations of synthetic herbicides with the fungal biocontrol agents was an approach adopted to enhance mycoherbicidal activity but had limited acceptance due to negative effects of their synthetic components. Hence a necessity for development of the formulations having least toxicity or being benign to non-target organisms was felt. The present study brings forth a new dimension of holistic and ecofriendly bioherbicidal formulations comprising of crude phytotoxins and spores of Alternaria alternata LC# 508 which enhances outstandingly its mycoher-bicidal potential. Spent broth of Alternaria alternata (LC#508) exhibited toxic activity to its spores (autotoxicity) at a concentration of 50μg/ml which was used for developing five formulations FN1 to FN5. Formulations No. 5 was the best of all the formulations when evaluated by pot trails compared to control and other formulations. Disease onset and mortality was observed in 3.5 days and 5 days respectively in case of formulation No 5(50 μg of crude spent broth + 1× 106 spores/ml) when compared to spore spray alone. Thus the formulation of crude spent broth and fungal spores could be developed as a cost effective and efficacious bioherbicide formulation when compared to the spores alone.