Critical period of weed harmfulness in sunflower crops of the central zone of the Krasnodar region

In 2022, we determined the critical pe-riod of weeds in sunflower sowings of the hybrid Aris in the central zone of the Krasnodar region. The re-search was conducted in fields of the Federal Scientific Center for Biological Plant Protection according to "Methodological guidelines for determination of criti-cal periods and economic thresholds of weed pests in crops" (1985). The soil of the experimental plots was leached chernozem. Weeds were represented by annual grass species (barnyard grass, yellow foxtail grass) and annual dicotyledonous species (common ragweed, vel-vetleaf, red-root amaranth, lamb's quarters, common cocklebur). The degree of weed infestation was high (132 specimens/m2). It was found that on plots infested within 10, 20, 30, 40, and 50 days after sunflower seed-lings emerged, there was a sharp decrease in yield – from 96.8 to 34.4% compared to the control without weeds. On the plots free of weeds during 10, 20, 30, 40, and 50 days, the yield increased significantly – from 58.3 to 97.7% in comparison with the control. On the basis of the obtained data, the value of the critical period of weed harmfulness on sunflower crops in the central zone of the Krasnodar region was established, which amounted to 24–25 days after the emergence of seedlings of cultivated plants.