Toxicity of three new selective insecticides on a nine-spot ladybird beetle, Coccinella novemnotata (Herbst) in Sebha, Libya

Under laboratory conditions of Plant Production labs, Fac. Agr. Sebha, Lybia, the susceptibility of three modern insecticides against ladybeetles adults was tested using direct exposure (dipping adults) or indirect exposure (feeding adults on the treated aphids). In the first experiment, based on the LC50 values after 24 hrs, spinosad showed the safest tested insecticide (1460.80 ppm) followed by spinetoram (1309.9 ppm). However, the acetamiprid was the most damage effect (0.15 ppm).On the same experiment; the results after 96 hrs were 1460.8, 999.17 and 0.13 ppm with the same insecticide with the same consequence order. In indirect bioassay after 24 and 96 hrs, the LC50 values recorded 852979.69, 706067, 478.18 and 913179.69, 2644.54, 478.18 ppm, respectively. In both exposure methods, spinosad keep the safest tested insecticide followed by spinetoram. While, the acetamiprid keep the last position. All tested insecticides were exhibited more safety in indirect exposure than direct exposure. To each insecticide, the aphis nerii aphids were dipped for 10 s in insecticide sublethal concentration/concentrations. The average numbers of aphid consumed by one adult of Coccinella novemnotata was recorded for three days after exposures. For spinosad, statistically there is no significant difference between the aphid consumption in the control and other concentrations in the first and second days. However, there is significant different between control and 400 ppm. For spinetoram, there is no significant difference between any treatments in the three days. For acetamiprid, there is no significant difference between control and 0.5 ppm.