Neem leaves, a potential source for protection of hardwood against wood decaying fungus
S Dhyani, S Tripathi, V K Jain
Neem leaves are widely recognized for their insecticidal, pesticidal, fungistatic and fungitoxic ability. The present study is to investigate the efficacy of neem leaves extractives against wood destroying microbes, a brown and a white rot. Neem leaves extractives prepared in various solvents such as petroleum ether, acetone, ethanol, methanol and hot water were tested at a concentration levels of 0.5%, 1.0% and 1.5% against Poria monticola,a brown rot and Polyporous versicolor, a white rot by malt agar method. The extracts showing higher efficacy in the petri plate were then subjected to soil block bioassays. The methanolic and ethanolic extract revealed high efficacy by inhibiting of the growth of both of the test fungus upto 98-99% at a very low concentration of 0.5%. While the acetone extract inhibited the growth of the brown and white rot upto 50 and 60% respectively, at its high concentration (1.5%). On the contrary the hot water and petroleum ether extractives promoted the growth of both the test fungus upto 100% at all the concentration levels. These results were observed in the petri plate by malt agar method. The extractives exhibiting higher efficacy in petri plate were then tested for their efficacy on poplar wood against the test fungus at a concentration levels of 1.5%, 3% and 4.5%. Blocks treated with the MeOH, EtOH and Acetone extracts of neem leaves reported a weight loss of 16%, 18% and 27% respectively against Poria monticola at a concentration level of 4.5%. While a weight loss of 21%, 22% and 26% was observed in the case of Polyporous versicolor at 4.5% concentration. Control samples exhibited a weight loss of 68 and 67% by both the fungus. Thus extractives treatments protected wood efficiently at laboratory scale.
Qualitative estimation of the extractives revealed a high amount of phenolics and small amount of flavonoids in MeOH and EtOH extractives. Acetone extract showed small amount of phenolics and traces of flavonoids while the hot water extract contained a large amount of carbohydrate and slight presence of phenolics.
Keywords: Neem, fungitoxic, extractives, brown rot, white rot, poplar, phenolic, flavonoid