Abstract

In 2007 and 2008 the field experiment was conducted to test the efficacy of three environmentally friendly insecticides against the Colorado potato beetle (Leptinotarsa decemlineata), with the aim of evaluating their effect on the yield of potato. 0.25 % water emulsion of Neem-Azal (active ingredient azadirachtin) was applied twice, while 3 % water emulsion of Aktiv (a.i. potassium salt of fatty acids) and 1 % water emulsion of Prima (a.i. refined rape oil) were applied eight times. In 2007, the potato yield was higher (25.3±3.2 t ha^-1) than in 2008 (8.2 ± 0.8 t ha^-1). In 2007 there were no significant differences in potato yield at different control measures and the yield ranged from 7.5 ± 1.3 t ha^-1 (Aktiv) to 9.4 ± 1.8 t ha^-1 (Prima). In 2008, the highest potato yield was recorded in Neem-Azal treatment (3.5 ± 0.7 t ha^-1), while in two other insecticide treatments the potato yield did not differ significantly with control treatment neither with the Neem-Azal treatment. Potato tubers were classified into three fractions: fraction 1 (tubers <4 cm), fraction 2 (tubers between 4 and 5 cm), and fraction 3 (tubers > 5 cm). On average we produce 2.11 ± 0.06 t ha^-1, 9.93 ± 0.53 t ha^-1, and 13.17 ± 0.70 t ha^-1 of potato in 2007, and 2.11 ± 0.20 t ha^-1, 4.68 ± 0.37 t ha^-1, 0.84 ± 0.29 t ha^-1 of potato in 2008, respectivelly.

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