Herbicides of soil action in a system of oil flax protection against weeds on the south of Russia

Since there are no pre-emergence herbicides in “The State Catalogue of pesticides and agrochemicals” approved for use in the Russian Federation on oil flax, in 2018-2020, we studied the pre-emergence herbicides on crop sowings in the zone of unstable moistening on leached chernozem (VNIIMK, Krasnodar) and in the zone of insufficient moistening on ordinary chernozem (Don experimental station of VNIIMK, Rostov region). We observed the decrease in weed infestation in oil flax sowings when we applied pre-emergence herbicides. The highest biological effectiveness was observed in the zone of unstable moistening, when the plants were sprayed with Tifi, WDG (0.025 kg/ha) at the stage of true leaves development of flax on the background of preemergence application with Frontier Optima, EC (1.2 l/ha) - 63.2%; in the zone of insufficient moistening -at pre-emergence application with the tank mixture Dual Gold, EC (1.6 l/ha) + Gezagard, SC (3.5 l/ha) -67.8%. However, we recorded the phytotoxic effect on oil flax at application of the tank mixture Dual Gold, EC (1.6 l/ha) + Gezagard, SC (3.5 l/ha) in the amount of 23.7-35.7% on the EWRC scale (European Weed Research Council). We established the positive effect of pre-emergence soil herbicides Frontier Optima, EC (1.2 l/ha) and Dual Gold, EC (1.6 l/ha) on the oil flax seed yield and economic indicators of its production. Herbicides Frontier Optima, EC (1.2 l/ha) and Dual Gold, EC (1.6 l/ha) are recommended for inclusion into the list of preparations approved for use on oil flax in the Russian Federation. Crop foliar treatment with herbicide Tifi, WDG (0.025 kg/ha) on the background of pre-emergence application of the preparation Frontier Optima, EC (1.2 l/ha) or Dual Gold, EC (1.6 l/ha) in the zone of unstable moistening led to yield decrease by 0.29 and 0.23 t/ha, respectively, it did not affect the oil flax yield in the zone of insufficient moistening.