Efficacy of Leaf Extracts of Neem (Azadirachta indica) and Chinaberry (Melia azedrach) Against Early Blight and Wilt Diseases of Tomato

The efficacy of leaf extracts of neem (Azadiracta indica) and chinaberry (Melia azedarach) against two tomato pathogenic fungi Alternaria solani and Fusarium oxysporum, the causal agents of early blight and wilt diseases of tomato plants respectively were studied. A comparison between the in vitro activity of neem and chinaberry leaf extracts against these two pathogenic fungi were investigated. Leaf extracts of different concentrations (5%, 10%, 15% and 20 %) of aqueous, ethanol and ethyl acetate of neem and chinaberry were added to growth media prior to inoculation. Inhibition values recorded a characteristic variation between neem and chinaberry. In case of neem, inhibition percentages were 17.88%, 23.66, 52.77 % and 70.55% for Alt. solani in the four used concentrations, while those for F. oxysporum were 14.77 %, 23.88%, 31.22 % and 100%, respectively. The corresponding values with chinaberry leave extracts were 3.11 %, 5.22%, 5.53 % and 5.77 %, recorded for Alt. solani and 5.44 %, 6.11 %, 6.35 % and 6.55% for F. oxysporum . Both ethanol and ethyl acetate extracts of neem leaves assayed at a concentration of 20%, completely suppressed the growth of F. oxysporum and inhibited Alt. solani by ratios between 52.44% and 62.77%, the same extracts but from chinaberry (20%) slightly inhibited the growth of both pathogenic fungi and values of inhibition not exceeded the 7 %. All used concentrations of neem extract effectively suppressed the mycelial growth of both pathogenic fungi and this effect gradually increased with increasing concentration. In addition, tests on activity of the main component, nimonol purified by HPLC as a separate component from neem ethyl acetate extract (mother extract), it gave no inhibition activities at all concentrations. Pathogenicity tests in vivo by Alt. solani showed disease incidence of 53.20 and 100 % after 2 and 4 weeks. Spraying tomato plants with 20% aqueous neem leaf extracts lowered the disease incidence to 42.54% while spray and irrigation reduced disease incidence to 39.49%. Spray and irrigation with 20% aqueous extracts from neem leaves seemed to work in a synergism in controlling the disease. Disease severity and control of tomato plants were also studied after 2 and 4 weeks of pathogen inoculation, results indicated that higher control ratios were also obtained in plants sprayed and irrigated with the aqueous extracts and values recorded were15.36% and 43.71% after 2 and 4 weeks, respectively with an increase in the disease severity for all treated plants by the progress of inoculation time. Concerning F. oxysporum, the effect of (20%) aqueous neem leaf extracts on seed germination, disease incidence and disease control of tomato plants were studied, results showed that the highest percentage (100%) of seed germination was obtained with -ve control (seeds + water) and seeds irrigated with neem leaf extracts, while the lowest one (70%) was recorded with +ve control (seeds + water + pathogen). Regarding disease incidence, the highest value (94.29%) was recorded with +ve control while the lowest (19.04%) was recorded with seeds treated with pathogen and irrigated with neem aqueous extracts whereas the highest disease control (80.96%) was recorded for seeds treated with pathogen and irrigated with neem extract. Neem extracts which are cheap and environmentally safe, exhibited considerable control of disease development and may be considered promising for protection of tomato plants against early blight and wilt pathogens with possible improvement of this economic crop.