In-vitro evaluation of plant extracts against Lasiodiplodia theobromae causing cashew inflorescent blight

Abstract

Extracts of four plant species, red acalypha (Acalypha hispida), siam weed (Chromolaena odorata), aidan (Tetrapleura tetraptera), and neem (Azadirachta indica) were screened in-vitro for fungitoxicity against Lasiodiplodia theobromae (cashew inflorescence blight pathogen) at four different concentrations viz., 10, 20, 40 and 80%. The result shows that the plants extracts significantly (P < 0.05) reduced mycelia growth of the fungus. The fungitoxicity of the plant extracts against L. theobromae also varied with concentration. Extract from T. tetraptera exhibited maximum efficacy in reducing the mycelia growth of L. theobromae to 9.83 mm at 80% concentration while the highest mycelia growth of 59.33 mm was recorded in extract ofi at 40% concentration. C. odorata at 10% concentration reduced the colony diameter to 50.50 mm while 20% T. tetraptera inhibited the pathogen to 42.33 mm. The percentage reduction in colony diameter by each of the phytoextracts ranged between 30.20 and 88.44%. Findings from this study reveal the possibility of utilizing naturally available plant chemicals for controlling L. theobromae with the ultimate goal of eliminating pesticide residues in the marketable products of cashew.

Key words: Cashew, Lasiodiplodia theobromae, inflorescent blight, plant extracts