Potentials of Aqueous Extract of Pod Husk Parkia biglobosa (Jacq.) Benth as a Biopesticide in Okra (Abelmoschus esculentus (L.) Moench) Production

摘要

Aims: This study evaluated potentials of aqueous extract of pod husk of Parkia biglobosa as a biopesticide in okra production. Study Design: The study employed a radomized complete block design with seven treatments (5, 10, 15 and 20% Parkia biglobosa aqueous pod husk extract (PPHE), 2.5 ml dimethoate + cypermethrin (D+C) – recommended, 5.0 ml (D+C), control – 500 ml of water) and replicated three times. Place and Duration of Study: Crop Garden of Department of Crop Protection and Environmental Biology, University of Ibadan (7° 34’N and 3° 54’E) between April and July 2016. Methodology: The leaves, seeds, pod husks and bark of Parkia biglobosa were collected, authenticated and analyzed for their phytochemical compositions using standard procedures. Aqueous extract of the pod husk of the plant (PPHE) was found to contain the highest phytochemicals qualitatively and quantitatively which formed the basis of using it as a biopesticide. A field study was conducted at the crop garden of Department of Crop Protection and Environmental Biology, University of Ibadan, to assess the potency of the extract as a biopesticide and a synthetic insecticide - Dimethoate 14.5% + Cypermethrin 5.5% (D+C) on the management of flea beetles on NHAe-47-4 okra variety. The seven treatments (5, 10, 15 and 20% Parkia biglobosa aqueous pod husk extract (PPHE), 2.5 ml dimethoate + cypermethrin (D+C) – recommended, 5.0 ml (D+C) (synthetic), control – 500 ml of water) were applied weekly on okra plants from two Weeks After Sowing (WAS) till 12 WAS. Data were collected on growth and yield parameters, dry matter accumulation of A. esculentus and flea beetle populations. Data were analyzed using descriptive statistics and ANOVA at P = 0.05. Results: Results revealed that treatment 20% PPHE had relatively higher values of growth parameters which compared favorably (p≤0.05) with 2.5 ml and 5 ml (D+C). Yield parameters; Number of fruits and fruit weights from 20%PPHE also compared favorably with 2.5 ml and 5 ml (D+C) with no significant difference ( P >0 .05) and with the same trend in dry root weight. While the dry shoot weight of 2.5 ml (D+C) treatment (p≤0.05) was different from other treatments. The control treatment however, revealed significant differences (p<0.05) in having reduced growth and low yield when compared with the treated plots. Conclusion: This study showed the efficacy and potency of Parkia biglobosa aqueous pod husk extract (PPHE) in suppressing the flea beetles due to its highest quantities of phytochemicals. The 20% concentration also enhanced the growth and yield of okra and performed relatively well with the recommended dose (2.5 ml) of D+C. The aqueous pod husk extract, therefore could serve as a biopesticide for food sustainability and safety.