Susceptibility of third instar Melolontha spp. white grubs to the contact action of neonicotinoid insecticides

Susceptibility of third instar [Melolontha] spp. white grubs to the contact action of neonicotinoid insecticides Experiments were conducted on the susceptibility of third instar [Melolontha] spp. white grubs to the contact action of neonicotinoid insecticides under laboratory conditions. The insecticides used were: a) SP and WG (water suspension) formulations: acetamiprid (Mospilan 20 SP containing the active substance at 200 g l[-1]), clothianidin (Apacz 50 WG containing the active substance at 500 g kg[-1]); b) GR (granular) forms: clothianidin (traditional formulation containing the active substance at 10 g kg[-1]), imidacloprid (slow release form containing the active substance at 50 g kg[-1]); and carbosulfan as a standard insecticide (GR slow release form containing the active substance - Marshal Suscon 10 CG - at 100 g kg[-1]). The experiments confirmed the low sensitivity of third instar [Melolontha] white grubs to the contact action of these insecticides. Insecticides of SP and WG formulations applied to the soil at a dose of 25 mg active substance kg[-1] soil did not cause 100% mortality after 28 days of exposure. In the case of clothianidin, mortality after 28 days was 40% and in the case of imidacloprid it was 80%. GR forms containing clothianidin (traditional formula) used at a dose of 50 mg kg[-1] soil, and imidacloprid (slow release form) used at a dose of 250 mg kg[-1] soil, caused 70 - 80% mortality after 28 days. Carbosulfan GR (slow release form), used as a standard at a dose of 500 g active substance kg[-1] soil, caused 100 % mortality after 28 days.