Sunflower is a strategic crop for Ukraine, the area under crops in 2022 was 4,573.8 thousand ha. Sunflower crops in the first stages of their development can be severely suppressed by weeds. The main threat is dicotyledonous weed species, for the control of which representatives of several classes of herbicides are recommended. However, all these herbicides should be applied to the soil before the emergence of sunflowers and weeds, the effectiveness of which depends on soil moisture and decreases sharply in drought conditions. The range of herbicides that can be used on sunflower vegetation and are effective against dicotyledonous weeds is extremely limited. In particular, the herbicide aclonifen is recommended for use during sunflower vegetation. However, the selectivity for sunflower when applied during the growing season is insufficient, as a result of which there is a high probability of temporary suppression of the crop. So, it is important to find a partner for simultaneous use with aclonifen in order to increase the selectivity of aclonifen due to the interaction effect. Significant changes in the selective phytotoxicity of aclonifen, which is carotenoid synthesis (CS) inhibitor, can be expected in the mixtures with herbicides — inhibitors of electron transport in photosystem II (PS II) of chloroplast. However, herbicides of this class, in particular prometryn, are recommended for use in sunflower crops only before emergence. At the same time, it is possible that reducing the rate of prometryn application to the subherbicidal level will allow to use it in the mixtures after sunflower emerging. Therefore, the purpose of this research was to investigate the effect of interaction, the effectiveness of weed control and the selectivity for the crop depending on the rates of aclonifen and prometryn applying alone and in the mixtures after emergens of sunflower. It was shown that interaction of aclonifen and prometryn for dicotyledonous weed species is synergistic or additive, in the range of aclonifen recommended application rates from 0.6 to 1.2 kg/ha and in the reduced to the subherbicidal rates of promethrin from 0.5 to 0.05 kg/ha. That ensures the high efficiency of the mixture for the control of wide range of dicotyledonous weed species. At the same time, due to synergism there was a sharp increase in phytotoxic effects of the mixture on sunflower, even with the minimum application rate of aclonifen of 0.6 kg/ha and the subherbicide rate of prometryn of 0.05 kg/ha, at which prometryn had practically no effect on weeds and sunflower. As a result, the use of the mixtures of aclonifen and prometryn after emergence of sunflower is not advisable. At the same time, the obtained results testify to the high probability of synergistic interaction of herbicides ? CS inhibitors joined use whis ET inhibiting herbicides, which can be used for the elaboration of herbicide compositions for the protection of other agricultural crops.
Keywords: Helianthus annuus L., interaction of herbicides, synergism, aclonifen, prometryn
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