In the laboratory experiment, which was taken place at the Slovenian Institute of Hop Research and Brewing (Department of Plant Protection) in Žalec, we studied the effectiveness of different active substances (azadirachtin A, natural pirethrin, spinosad, caolin clay, and wood ash) against the adults of cabbage flea beetle Phyllotreta atra. The substances were compared with the standard active ingredient lambda-cihalothrin, which contains the product Karate Zeon 5 CS. Each product have been tested in five repetitions. The solutions of products were applied on the leaves of cabbage with the apparatus Potter's Tower. The solution of CutiSan (caolin clay) was applied with a bottle with a spray, while wood ash (mainly of beech) was applied with a nylon socks. In each Petri dish with the treated cabbage leaves we added 10 adults of cabbage flea bettle, and then we placed them in upholstery container, which we set up in the laboratory at room temperature and exposed to daily light. For control, we used the cabbage leaves, which we sprayed only with water. The effectiveness of the products we have evaluated 2, 3, and 5 days after application; we determined the mortality rate (mortality) of beetles, visually determined the percentage of damage caused by the beetles on the cabbage leaves, and calculated the % of efficiency of each active substances according to the Abbott's formula. On the basis of the results of our research, we can conclude that the adults of Phyllotreta atra oppress the most preparations with the contact and the gastric action. In our study, the two most effective active substances have proven to be spinosad and lambda-cihalothrin. The lowest efficacy showed the active ingredient azadirahtin A due mainly to its slow action.
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