The in vitro effect of five commonly used herbicides viz., pyridate, fluazifop-P-butyl, foramsulfuron, tembotrione and S-metolachlor on mycelial growth of entomopathogenic fungus Beauveria bassiana (ATCC 74040) was evaluated each at different concentrations: 100, 75, 50, 25, 12.5, 6.25 and 0% of recommended field application rate on PDA agar plates at 15 and 25°C. The herbicides tested were classified in 1-4 scoring categories based on reduction in mycelial growth: 1 = harmless (<25% reduction), 2 = slightly harmful (25-50%), 3 = moderately harmful (51-75%), harmful (>75%) in toxicity tests. All the five herbicides had fungistatic effect to B. bassiana at varying intensities depending on their concentrations in medium. The present study showed that B. bassiana is very sensitive to the herbicides tested, particularly at recommended as well as lower field dosage. The selected herbicides foramsulfuron, tembotrione and S-metolachlor have strong fungistatic effect on mycelial growth (> 75% inhibition) at 15 °C and concentrations from 50 to 100%. Foramsulfuron has fungicidal effect at 100 % concentration. Foramsulfuron, tembotrione and S-metolachlor were less inhibitory at 25 than at 15 °C, but the temperature had no influence on reduction of mycelial growth at pyridate and fluazifop-P-butyl. Of the herbicides tested, pyridate and fluazifop-P-butyl showed less adverse effects and are probably compatible with B. bassiana in the field. However, extensive field studies complemented by parallel laboratory experiments should consider assessing the interaction between selected herbicides and B. bassiana isolates to evaluate their ecological impact in cropped environments. V in vitro poskusih smo na PDA agarnih ploščah in temperaturah 15 ter 25 °C preučevali učinek petih pogosto uporabljanih herbicidov, in sicer piridata, fluazifop-P-butila, foramsulfurona, tembotriona in S-metolaklora na rast micelija entomopatogene glive B. bassiana (ATCC 74040) pri različnih koncentracijah: 100, 75, 50, 25, 12,5, 6,25 in 0 % priporočenega poljskega odmerka. Glede na inhibicijo rasti micelija smo po toksikoloških testih preučevane herbicide razvrstili v štiri razrede: 1 = neškodljiv (<25 % inhibicija), 2 = malo škodljiv (25 - 50 %), 3 = zmerno škodljiv (51 - 75 %), 4 = škodljiv (> 75 %). Vseh pet herbicidov ima fungistatičen učinek na glivo B. bassiana, na obseg pa vpliva njihova koncentracija v gojišču. Raziskava je pokazala, da je gliva B. bassiana zelo občutljiva na preizkušane herbicide, posebej pri priporočenih poljskih koncentracijah, pa tudi pri manjših odmerkih. Pri temperaturi 15 °C in koncentracijah od 50 do 100 % imajo herbicidi na podlagi foramsulfurona, tembotriona in S-metolaklora izrazit fungistatičen učinek (> 75% inhibicija), pri 100 % odmerku pa ima foramsulfuron celo fungicidni učinek. Foramsulfuron, tembotrion in S-metolaklor so bili manj inhibitorni pri 25 kot 15 °C. Temperatura ni vplivala na inhibicijo rasti micelija pri piridatu in fluazifop-P-butilu. Od vseh preizkušanih herbicidov sta imela piridat in fluazifop-P-butil najmanj zaviralnih učinkov in bi jih lahko uporabljali na pridelovalnih površinah skupaj z glivo B. bassiana. Poleg laboratorijskih testov s herbicidi bi morali izvajati vzporedne poskuse na pridelovalnih površinah, da bi dejansko izvrednotili njihov ekološki vpliv na glivo B. bassiana