Managing Acanthoscelides obtectus Say on Stored Phaseolus lunatus L. with Six Indigenous Botanical Powders

Telfairia occidentalis, Piper guineensis, Gmelina arborea, Bryophyllum pinnate, Amaranthus viridis, and Musanga ceropolides were separately assessed for insecticidal effects on Acanthoscelides obtectus Say, a pest of stored Phaseolus lunatus L. The plants were assessed in a completely randomized design for aduticidal and reproductive inhibition potential as well as effect on seed weight at three treatment doses (2%, 4%, 6% and 0 as the control). Results showed that at 144 hours post-treatment, P. guineensis at 6% dose had the highest significant (P=0.05) mortality (59.5%) of A. obtectus. This was followed by P. guineensis which had comparable effect 2% (50.9%) and 45 (54.9%). The least significant mortality was observed in control. At 4% and 6% A. viridis had similar mortality effect on A. obtectus as 6% G. arborea, while 2% A. viridis, 6% B. pinnate, 2% and 4% G. arborea had similar effect. The highest number of progeny emerged after 49 days were observed in control (345.33±8.84) while P. guineensis significantly (P=0.05) inhibited progeny followed by 6% G. arborea and 6% M. ceropolides. Phaseolus lunatus seeds treated with 6% P. guineensis also had the least significant weight loss while the control had the greatest weight loss of 32.56 g. Though all these test plants significantly (P=0.05) increased adult mortality, reduced progeny emergence and weight loss in seeds than the control. Piper guineensis however, exhibited the best insecticidal property. Piper guineensis and G. arborea were significantly more active in inhibiting A. obtectus reproduction and progeny emergence, but increased adult mortality leading to reduction in weight loss.

Bioactive metabolites of Senna didymobotrya used as biopesticide against Acanthoscelides obtectus in Bungoma, Kenya.

Post-harvest pests are known to cause severe losses of beans in particular the bean weevil, Acanthoscelides obtectus, necessitating immediate and long term control measures. Convectional pesticides have been used for decades to protect stored grain from pests, but their harmful environmental impact and pest resistance resulting from the need for increased pesticide use have triggered researchers to search for eco-friendly, biodegradable and potent biopesticides. The use of natural products derived from metabolic activity of plants may constitute a new avenue of pest control. This paper describes phytochemical and biological investigations of leaves, root, and stem bark crude extracts and isolated compounds of selected Kenyan plants used to control the bean weevil. Bioassays tests of the compounds were done against brine shrimp to test their insecticidal activity against the bean weevil. Antibacterial and antifungal activity of the crude extracts of S. didymobotrya was also done. The extracts of S. didymobotrya showed high toxicity as well as adulticidal activity against bean weevil.