Journal of Applied Biosciences (J. Appl. Biosci.) [ISSN 1997 - 5902]
Volume 43: 2899 - 2914. Published July 11, 2011.
Bio-insecticidal effects of plant extracts and oil emulsions of Ricinus communis L. (Malpighiales: Euphorbiaceae) on the diamondback, Plutella xylostella L. (Lepidoptera: Plutellidae) under laboratory and semi-field conditions
Tounou Agbéko Kodjo*, Mawussi Gbénonchi, Amadou Sadate, Agboka Komi, Gumedzoe Yaovi Mawuena Dieudonné and Sanda Komla
Ecole Supérieure d’Agronomie (ESA), Université de Lomé (UL), BP 1515 Lomé-Togo;
*Author for correspondence, Email: ktounou@gmail.comABSTRACT
Objective: The objective of this study is to evaluate the potential of using Ricinus communis leaf, root, seed kernel crude extracts and oil emulsion to control the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae).
Methodology and results: The effect of different treatments of R. Communis plant extract (20%) and oil emulsion (5% and 10%) and their persistence (0, 3 and 5 days after application; DAA) on mortality and oviposition behaviour of P. xylostella were tested in laboratory and field cage experiments. In general, R. communis products have strong larvicidal effect on P. xylostella, with 100% mortality recorded on 3rd instar larvae treated with 10% oil emulsion in both ingestion and contact toxicity tests. Aqueous extracts were significantly less toxic with the highest mortality rates (67.49 ± 1.98% and 70.86 ± 0.85%) recorded with seed kernel extract and the lowest with the root extract (53.98 ± 1.21% and 54.87 ± 1.88%), in topical toxicity and ingestion toxicity experiments, respectively. The adult emergence was significantly affected with the lowest emergence rate recorded in 5% oil emulsion, 57.72 ± 72% and 49.98 ± 0.98% in topical toxicity and ingestion toxicity tests, respectively. No significant different was noted between Dursban and aqueous extract treatments. Among emerged adults from larvae treated with oil and aqueous extracts, a 44–79% abnormal development as wings and legs deformation were observed. The sex ratio was skewed in favour of males among F1 progeny from Durban and R. communis treated insects and in favour of females in controls. In field-cage experiments, treated plants had strong larvicidal and oviposition deterrent index on P. xylostella. The oviposition deterrence index was highest with castor bean oil at a concentration of 10%. Diamondback females clearly discriminated between plants sprayed with R. communis products and those with water. Treating diamondback-infested cabbage plants with plant extracts and oil emulsions resulted in more than 59% mortality 7 DAA. Experiments on the residual effects revealed a significant decrease in larval mortality with time between the botanical application and insect release.
Conclusion and application of findings: In view of the low oviposition rates, oviposition deterrent, immature mortality, and the relatively low persistence of the toxic ricin oil, it can be expected that the use of R. communis product be suitable for P. xylostella population density reduction in the field.
Key words: botanicals, Ricinus communis, integrated pest management, Oviposition, Plutella xylostella.
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