Pg. 36-40 Biological Control of Litchi Fruit Diseases

Microbial epiphytes isolated from chemically sprayed and unsprayed litchi trees, yielded three promising antagonists, later identified as Bacillus stearotermophilus, Bacillus megaterium and Bacillus licheniformis. These isolates effectively inhibited Phomopsis sp, Pestalotia sp, Alternaria alternata, Penicillium sp and seven unidentified litchi post-harvest pathogens, when evaluated in vitro. Optimisation studies revealed that post-harvest decay was more effectively reduced with B megaterium applied as a fine spray compared to dip application. It was found that 10⁸ cells/ml B licheniformis was the most effective antagonist concentration to reduce post-harvest decay, while all concentrations (10⁶, 10⁷ and 10⁸ cells/ml) were equally effective in reducing post-harvest infections. Additives (Agral 90 and L-alanine and glucose) were equally effective in enhancing the ability of B stearotermophilus to reduce litchi post-harvest fruit infection. Antagonists applied as a dip singly or in a mixture were more effective in reducing decay, post-harvest infection and fruit browning, than a warm water Benlate treatment. B subtilis (originally isolated from the avocado phylloplane) was also more effective in reducing litchi post-harvest fruit infection when compared to the Benlate chemical treatment.