Toxicity of spinosad, two nicotinoids, acetamiprid and imidacloprid, and two
conventional insecticides, chlorpyrifos and cypermethrin were tested in the field
against two aphid species, Rhopalosiphum maidis (Fich) and Schizaphis graminum
(Rondani) infesting two sorghum varieties, Horus and Dorado. R. maidis
started to infest the two sorghum varieties by the last week of June and continue
till the first half of August. While, S. graminum started to infest both sorghum
varieties by the first week of August and continue till the third week of September.
Two spray treatments were conducted by Knapsack sprayer the first one was
in June 30th and the 2th second was in August 7th. Reduction percent in the number
of aphid eggs and nymph due to the insecticide treatments was calculated 3,
17, and 37 days after treatment. Eggs and nymphs of population R. maidis and S.
graminum were strongly decreased in all treated Horus and Dorado varieties after
3 days from insecticides application as compared with control. Spinosad and
nicotinoid compounds were more effective than the two conventional insecticides,
chlorpyrofos and cypermethrin in controlling both species of aphid, on the
two sorghum varieties. The descending order of the insecticides activity was imidacloprid,
acetamiprid, spinosad, chlorpyrifos and cypermethrin in all experiments
of this study.