Phytochemical and insecticidal properties of some botanical extracts against the lesser grain borer, Rhyzopertha dominica F. (Coleoptera: Bostrichidae)

Abstract

UMYUK) Nigeria, to analyze phytochemical properties and assess insecticidal effects of acetonic leaf extracts of Euphorbia balsamifera, Lawsonia inermis and Mitracarpus hirtus against Rhyzopertha dominica F. To analyze the phytochemicals of the test plants, preliminary tests were conducted to determine secondary metabolites while Gas Chromatography Mass Spectrum (GC-MS) was carried out to identify various active compounds present in the botanical extracts. Effects of the treatments on adult mortalities against R. dominica, adult emergence and grain weight losses were also determined. To determine percentage mortalities of R. dominica at 7 days after treatment (DAT), acetonic extracts of the botanicals at the concentrations of 6.25, 12.50, 25.00, 50.00, 100.00 mgml -1 and permethrin powder at 11.20 mg/20 g were applied to 20 g of sorghum grains in different plastic bottles. None of the extracts or permethrin powder was added to the control. The experiment was arranged in a completely randomized design (CRD) and replicated three times. Findings of the study revealed the presence of alkaloids, carbohydrate, phytesterols, phenolic compounds, flavonoids, saponins, tannins and cardiac glycosides in the botanical extracts. The plant extracts resulted in adult mortality of R. dominica which ranged from 16.67 to 63.33% within 7 days after treatment (DAT). No adult emergence was observed in all the treated grains. Also, grain weight losses of the treated sorghum varied from 3.92 to 6.63%. Acetonic extracts of the botanicals could therefore be utilized to reduce R. dominica infestations in stored sorghum.

Potentiality of some botanical extracts as biopesticides against the maize weevil, Sitophilus zeamais Motsch. (Coleoptera: Curculionidae)

“…This finding concurs with a previous report that ethanolic leaf extract of M. hirtus caused total mortality of S. zeamais at 3 DAT when applied at 50.00 mgml -1 [34] . Another report indicated that 100.00 mgml -1 acetone extract of M. hirtus resulted in 63.33% adult mortality of R. dominica at 7 DAT [24] . This study has revealed that high mortality of insects exposed to plant extracts might have exhibited contact toxicity against the weevils as suggested by Hikal et al [35] .…”

“…This was possible because plant species contain secondary metabolites which are vast storehouse of compounds such as the steroids, phenolic compounds and tannins with wide range of biological activity reported to have great impact on insecticidal activities [35,37] . Other bioactive compounds such as terpenoids, flavonoids, alkaloids, saponins and glycosides were found in the leaf extracts of E. balsamifera, L. inermis and M. hirtus [24] . GC-MS analysis confirmed the presence of different compounds sucn as oileic acid Eicosyl ester, decanoic acid, hydrogen peroxides and N,N-diethyl nediamine in acetonic leaf extracts of E. balsamifera, L. inermis and M. hirtus and found to have some insecticidal properties [24] .…”

“…Other bioactive compounds such as terpenoids, flavonoids, alkaloids, saponins and glycosides were found in the leaf extracts of E. balsamifera, L. inermis and M. hirtus [24] . GC-MS analysis confirmed the presence of different compounds sucn as oileic acid Eicosyl ester, decanoic acid, hydrogen peroxides and N,N-diethyl nediamine in acetonic leaf extracts of E. balsamifera, L. inermis and M. hirtus and found to have some insecticidal properties [24] .…”

“…Previous findings proved that a vast number of botanicals are toxic against S. zeamais [19,20,21,22] . In view of the promising effects of some botanicals against insect pests of stored products, Euphorbia balsamifera Aiton, Lawsonia inermis L. and Mitracarpus hirtus (L.) DC were selected for this study due to their reported bioactive compounds which have been suggested to be of insecticidal importance [18,23,24] .…”

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“…One of the challenges of the application of plant products as bio-pesticides in Nigeria is that most of the data are obtained from laboratory experiments with little from field trials. Abubakar et al [93] observed that most of the laboratory evaluations did not address the aspect of lethal concentrations of botanicals against insect pests. It is important that researchers need to look into this aspect to investigate on lethal doses/concentrations of various botanicals with insecticidal potentials.…”