Evaluation of Worm-Bed Leachate as an Antifungal Agent against Pathogenic Fungus, Colletotrichum gloeosporioides

Abstract

ABSTRACT Worm-bed leachate is a nutrient-rich by-product of composting organic wastes with earthworms. Worm-bed leachate was stored and characterized while its possible antifungal activity towards the pathogenic fungus Colletotrichum gloeosporioides (Penz.) Penz. and Sacc. was investigated in vitro. The pH decreased from 9.6 at the onset of the storage to 8.9 after 28 days, while the total N and C nearly halved. The surfactin concentration in the worm-bed leachate reached 10.8 μg L−1 at day 10, while that of iturin A and iturin A homologues increased towards the end of the storage. Sterilized worm-bed leachate had little effect on the growth of C. gloeosporioides, but unsterilized worm-bed leachate inhibited growth 100%. It was found that unsterilized worm-bed leachate inhibited growth of C. gloeosporioides, but sterilizing the worm-bed leachate strongly reduced the inhibitory effect indicating that the microorganisms in the worm-bed leachate out-competed the fungus for nutrients or were antagonistic towards it.