engleski

Control of the colorado potato beetle (Leptinotarsa decemlineata Say., Coleoptera: Chrysomelidae) with the combinations of the ecologically friendly insecticides

Research was done in order to investigate the efficacy of the combinations of the subnormal dosages of the ecologically friendly insecticides (neem extract, Bacillus thuringiensis var. tenebrionis, pyrethrin and spinosad) against CPB larvae. Two field trials and one laboratory trial were set up in 2001 and 2002. In 2001 the maximal number of larvae on untreated plots was 12 larvae/ plant, and in 2002, it was lower, 5, 5 larvae/plant. The efficacy of the B.t.t. insecticide in field trials was between 70 and 74%. The efficacy of the neem extract in 2001 was 73%, while in 2002, the efficacy was somewhat lower (54%). Efficacy of the pyrethrin was in both years between 86 and 89%. Residual activity of the B.t.t. insecticide, neem and pyrethrin lasted 7-9 days. The application of spinosad resulted in efficacy over 99%. Residual activity of spinosad lasted 14 days in 2001 and 21 days in 2002. Reduced dosages (33% of the full dose) of B.t.t. insecticides, neem extract and pyrethrin in combination with the reduced dose (33% of the full dose) of spinosad resulted in efficacies over 97% in both years. High residual activity of the combinations lasted 10 days in 2001 and 14-21 days in 2002. Results obtained in the field trials were confirmed in laboratory trial. Joint actions of insecticides in most cases were classified as independent synergism. With effect of the independent synergism of such combinations the economic and ecologic benefits are expected.

colorado potato beetle; neem extract; Bacillus thuringiensis var. tenebrionis; pyrethrin and spinosad

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