Effect of Carbaryl and Methyl Parathion on Adult Coleomegilla Maculata, 1995

Carbaryl and methyl para-thion, widely used insecticides for management of adult Diabrotica spp., were evaluated to determine their toxic effect on a common maize (Zea maize L.) inhabiting adult coccinellid, C. maculata. Adults were collected from field habitats in Brookings Co., SD during the second week of May 1995. Insects were returned to the laboratory and held in 30 cm diameter X 7 cm high plastic containers containing a cotton wick water source and wheat leaves infested with corn leaf aphids (Rhopalosiphum maidis [Fitch]). The laboratory was maintained at 24° C and 50% RH. After 48 h laboratory bioassays were conducted using technical grade carbaryl (99%) and methyl parathion (98%). Seven dilutions of each insecticide were prepared with acetone and ranged from 0.0005 to 0.2 u.g/u.1. An acetone control was also included. Five beetles/dilution were treated topically with 1 u.1 doses applied to the ventral surface of the insect. The beetles were then placed individually into 60 mm diameter petri dishes containing an agar water source. Mortality was recorded at 1, 2, 4 and 24 h after treatment. Insects were considered dead if no movement was noted after two probes with a dissecting needle. These experiments were repeated 3 times and data were combined for analysis. Data were analyzed using the POLO-PC Probit procedure (LeOra Software, 1987).