Newer Synthetic and Biorational Insecticides against Aphid, Rhopalosiphum maidis (Fitch) on Plantago ovata Forsk.

The relative efficacy of eleven insecticides against the aphid, Rhopalosiphum maidis (Fitch) revealed that dimethoate emulsion (0.03%) was the most effective followed by imidacloprid (0.005% solution), thiamethoxam (0.025% dispersion) and acephate (0.037% solution). Vertimec (9.5 mg a.i. L⁻¹ emulsion), spinosad (0.01% suspension) and diflubenzuron (0.05% emulsion) ranked in the middle order of effectiveness. Metarrhizium anisopliae (1×10⁸ spores L⁻¹), Beauveria bassiana (1 ×10⁸ spores L⁻¹), karanj seed extract (5 mL L⁻¹), and neem seed kernel extract (5 mL L⁻¹) were the least effective. The maximum yield was recorded from the plots treated with dimethoate (7.79 q ha⁻¹) followed by imidacloprid and thiamethoxam and the minimum from M. Anisopliae (5.37 q ha⁻¹). The highest benefit:cost ratio (39.51:1) was obtained in dimethoate treatment followed by acephate (36.92:1) and imidacloprid (24.84:1). Plots treated with spinosad showed negative benefit:cost ratio (0.28:1).