Summary The pot experiment on the possibility of tribenuron methyl dose reduction depending on the interaction of abiotic factors with weed growth stage under controlled conditions was carried out. The effect of the interactions between temperature (20/10 and 10/5°C) or relative humidity (75 and 50%) and weeds growth stage (2–4 and 6–8 leaves) was investigated. Tested plants were: Anthemis arvensis L., Papaver rhoeas L. and Stellaria media L. The herbicide was applied at the recommended and reduced doses (15 g a.s./ha and 7.5 g a.s./ha respectively) alone and in the mixture with adjuvant Trend 90 EC. Tribenuron methyl applied without adjuvant at the reduced dose efficiently controlled only S. media independently on relative humidity and growth stage of plants. The herbicide used at the reduced dose in the mixture with adjuvant Trend 90 EC was highly efficient against A. arvensis, P. rhoeas and S. media. Under optimal conditions, i.e. early growth stage and high temperature or relative humidity. Herbicide efficacy was more dependent on growth stage of weeds than on abiotic factor. Herbicide activity was weaker while applied at the reduced dose on older plants, even under higher temperature or relative humidity.