Effectiveness of neem (azadiracta indica) extracts for the control of fusarium oxysporum in pines (pinus patula)

Abstract

Fusarium wilt often leads to damping off and is an important disease of pine (Pinus patula) in the nursery. The use of chemicals as a control method is becoming less appealing because of the health implications as well as the high costs, which are often not within the reach of farmers in most of the developing world. Thus, neccesitates the evaluation of non-chemical methods of controlling the Fusarium. This study was conducted to evaluate effectiveness ofneem (Azadirachta indica) extracts for the control of Fusarium oxysporum in pines (Pinus patula). The specific objectives were to determine: (i) efficacy of A. indica extracts in controlling F. oxysporum growth (ii) effects of A. indica extracted from the leaves and bark on the germination of P. patula seed infested with F. oxysporum and (iii) effects of A. indica against F. oxysporum infesting the P. patula seedlings. Data were collected from KEFRI pathology laboratory between August and September 2006. A. indica was extracted from bark and leaves of neem tree using 99% ethanol followed by filtration while the seeds of P. patula were obtained from KEFRI, Muguga. Bioassay was done to test efficacy of A. indica extract on the growth of F. oxysporum. Seeds and seedlings of A. indica were first exposed to F. oxysporum followed by A. indica extracts applied at a concentration of 25%, 50%, 75% and 100% respectveiy to test for germination of seeds and performance of seedlings. Data collected were subjected to analysis of variance (One-Way ANOVA) and Tukeys's Post-Hoc comparisons. The results indicated that extracts of A. indica from the leaves were effective against F. oxysporum in concentrations above 25%. At that concentration (25%), A. indica extracts from the bark were more effective (t = 118.3342, df = 1, P < 0.001) against F. oxysporum as compared to leaves extracts. There was no significant differences (P > 0.05) in growth of F. oxysporum between the bark and the leaves at concentrations of 75% and 100%, of A. indica, resulted. There were significant differences in the germination percentages of P. patula (P < 0.05) among the leaf and bark extract treatments. Pre-emergence germination percentage was highest in the seeds treated with 25% A. indica extracted from leaves (68.3 ± 15.4%). Post-emergence germination of P. patula under 25% of the A. indica extract were highest both in the leaves and bark extracts. Death of P. patula seedling was significantly higher (P < 0.05) in untreated controls than all the other treatments. Among treatments, death of seedlings was lowest in 75% A. indica extracted from leaves and 100%A. indica extracted from the bark. These results clearly demonstrate that A. indica extracts at suitable concentrations are apt to control F. oxysporum thus is appropriate in managing damping off disease of P. patula. Thus, it is recommended that farmers should use the A. indica extract as a suitable nonchemical control methods against damping off disease in pines subject to further research to streamline the methods of application of the chemical by farmers.