Efficacy of different extracts of Rhamnus dispermus Ehrenb. (Rhamnales:Rhamnaceae) as aphicides against Eriosoma lanigerum (Hausmann)(Homoptera: Aphididae) and its parasitoid, Aphelinus mali (Hald.)(Hymenoptera: Aphelinidae)
Abstract: Botanical insecticides are important component of integrated pest management. Theaim of this study was to test the insecticidal activity of different extracts of Rhamnus dispermusEhrenb. against the woolly apple aphid (WAA), Eriosoma lanigerum (Hausmann) (Homoptera:Aphididae) and its parasitoid, Aphelinus mali (Hald.) (Hymenoptera: Aphelinidae), since it hasbeen shown that these extracts have insecticidal activity against the peach trunk aphid. Threeconcentrations (100, 1000, and 10,000ppm) of each extract were obtained by dissolving the dryextract in 0.01% solution of dimethyl sulfoxide (DMSO). All tested hexane, acetone, chloroformand ethanol extracts showed significant control on WAA nymphs and adults compared with thecontrol treatment. Both acetonic and ethanolic extracts of Rhamnus caused mortality to WAAadults (88 and 83%, respectively) and nymphs (94 and 89%, respectively) after 72h of exposureto the highest concentration. These extracts were as toxic as imidacloprid (used at therecommended field application rate of 0.25ml/l) on adults and nymphs of WAA (97 and 99%,respectively).Treatment of mummified aphids with the acetonic and ethanolic extracts of Rhamnus at thehighest concentration did not hinder the adult parasitoid development (more than 90% emerged);while the synthetic control, imidacloprid, highly hindered adult parasitoid development (8%emerged). After all, extracts from R. dispermus provided valuable mortality rates for the WAAwith very low effect to its parasitoid A. mali, and can be used as botanical insecticides in anintegrated pest management programs for this insect pest.