Repin buhač (Chaetocnema tibialis Illiger 1807) štetnik je ranog porasta šećerne repe, koji radi najveće štete na tek izniklom usjevu izgrizajući ne samo kotiledone nego i cijelu biljku, pa se čini da biljka nije ni iznikla. Odrasli oblici izgrizanjem lišća prave tipične okrugle rupice. Pri jakom napadu od 5 buhača na jednu repu u stadiju kotiledona, usjev biva uništen gotovo za jedan dan. Pojavi buhača pogoduju topliji i suši uvjeti koji pojačavaju njihovu aktivnost i ishranu na repi. Zaštita šećerne repe do sada se provodila tretiranjem sjemena sistemičnim insekticidima neonikotinoidima širom Europe, ali zbog poznatih problema vezanih na negativan utjecaj na pčele od 2018. nastupila je zabrana njihove uporabe i za ovu namjenu. Zato je iznimno važno utvrditi učinkovitost drugih djelatnih tvari koje bi mogle poslužiti kao adekvatna zamjena neonikotinoidima. Cilj ovog diplomskog rada bio je istražiti u laboratoriju učinkovitost djelatnih tvari klorantraniliprola, spinosada i azadirachtina, te ih usporediti s najčešće korištenim tiametoksamom iz skupine neonikotinoida. U laboratorijskom pokusu istražena je učinkovitost klorantraniliprola, spinosada, azadirachtina i tiametoksama primijenjenih tretiranjem sjemena šećerne repe na imaga buhača sakupljena na području Tovarnika. Svaki je insekticid primijenjen u tri doze. Tretiranje sjemena provedeno je u laboratorijskim uvjetima nakon čega su uzgojene biljke koje su ponuđene kao hrana buhačima. Pokus je očitavan tijekom 96 sati, a broj mrtvih buhača na insekticidu i kontrolnoj varijanti korišten je za izračun učinkovitosti po formuli Schneider – Orelli. Rezultati pokusa pokazali su da sve tri istraživane djelatne tvari mogu poslužiti kao zamjena tiametoksamu, unatoč razlikama u učinkovitosti korištenih djelatnih tvari. Najbolji učinak polučio je azadirachtin te spinosad, dok je učinkovitost klorantraniliprola bila slabija, ali i dalje zadovoljavajuća i u rangu učinkovitosti standardnog insekticida.

Sugar beet flea beetle (Chaetocnema tibialis Illiger 1807) is a pest of the early sugar beet growth who damages not only cotyledons but also the whole plant and makes appearance of ingrown plant. After feeding on the leaves, adult forms form typical small rounded holes. At heavy attacks of 5 beetles per one plant in the stage of cotyledons, the crop can be destroyed for almost a day. Their activity depends on weather conditions, where the warmer and dry weather increases their activity and feeding on the sugar beet leaves. The use of neonicotinoids in sugar beet seed treatments is widespread across Europe, but due to known problems related to the negative impact on bees, since 2018. their use has been prohibited for this purpose. Therefore, it is extremely important to determine the efficacy of other active substances that could serve as an adequate substitution for neonicotinoids. The aim of this master thesis was to investigate the effectiveness of insecticides containing active substances chlorantraniliprole, spinosad and azadirachtin in the laboratory conditions and compare their efficiency to the mostly used insecticide thiamethoxam from the group of neonicotinoides. After sugar beet seed treatment with chlorantraniliprole, spinosad, azadirachtin and thiamethoxam in a laboratory experiment, their efficacy on the sugar beet flea beetle collected in the area of Tovarnik was studied. Each insecticide was administered in three doses. Seed treatment was carried out in laboratory conditions, where after of plant growth leaves were used as food for beetles. The experiment was monitored for 96 hours and the number of dead beetles caused out from insecticides and control variants was used to calculate efficacy by the Schneider - Orelli formula. The results of the experiments have shown that all three of tested compounds may serve as a replacement for thiamethoxam, despite differences in the efficacy of the active substances used. Azidirachtin and spinosad showed the best effect on sugar beet beetle's mortality, while chlorantraniliprole was less effective but still gave satisfactory results in the range of standard insecticide efficacy.