Background. Thrips constitute a group of common maize pests in Poland. Although in recent years their population and harmfulness in maize fields have increased, they are still not covered by chemical control due to the lack of approved insecticides. Material and methods. A study was carried out in 2010-2012 in southeastern Poland to test the potential indirect effects of non-selective seed dressings and foliar insecticides applied in the spring to control the frit fly (Oscinella frit L.) on the population of thrips without the need for separate treatments. Seed dressings containing imidacloprid (Gaucho 600 FS and Couraze 350 FS) and methiocarb (Mesurol 500 FS), as well as foliar insecticides containing lambda-cyhalothrin (Karate Zeon 050 CS) and a mixture of thiacloprid with deltamethrin (Proteus 110 OD) were used in the experiment. Results. In the study years thrips infested maize plants from mid-May to the first ten days of October. They were most abundant from the end of June to mid-August, with a single population peak between 11 and 20 July. All the tested insecticides used in spring to control O. frit had an indirect insecticidal effect on thrips. The highest effectiveness of seed dressings and foliar insecticides was observed until mid-June, which did not allow for the effective protection of maize plants against feeding thrips. Conclusion. The insecticidal effect of the tested products ended before the most abundant occurrence of thrips, and, therefore, these pests have to be controlled separately with chemical treatments on later dates.

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