The effect of different herbicide application schemes on sunflower pollination by honey bees

It was highlighted that the effects of different weed-control schemes in sunflower (Helianthus annuus L.) influenced the activity of honey bees (Apis mellifera L.) and sunflower harvest quality. The experiment was conducted in 2022–2024 at the experimental field of the State Institution “Institute of Grain Crops,” National Academy of Agrarian Sciences of Ukraine (NAAS). Three sunflower hybrids were studied (Biloba CLP, NK Neoma, Suvex). The experiment design included hand weeding (control), two schemes with soil herbicides (Primextra TZ Gold + Yastrub; Eclipse + Fielder), and post-emergence herbicides (Helianthex; Stels; Challenge). Bee colonies were placed at 5 colonies/hа; visitation of sunflower heads was recorded by video monitoring (24 GoPro cameras) during peak bee activities. Based on the video materials obtained, the mean number of visits per head was assessed in three repeatabilities. The oil content was determined after threshing the plots. It was found that the control variant provided the greatest attractiveness for bees (6.11 visits/basket/10 min). Soil-applied herbicides reduced attractiveness by 29–56 % on average: the smallest reduction was recorded for Primextra TZ Gold + Yastrub (−29 %), and the largest for Eclipse + Fielder (−56 %). Post-emergence herbicides reduced visitation by 33-86 % (Challenge −33 %, Helianthex −82 %). In the dry year of 2024, bee activity was the lowest (1.28 visits/10 min). In terms of oil content, the smallest deviation from the control was observed for the herbicide protection scheme Primextra TZ Gold + Yastrub (−1.16 %), whereas the application of herbicide Challenge increased the oil content of the Suvex hybrid by 2.26 %. NK Neoma hybrid showed the highest stability. It was concluded that soil programs and the balanced use of post-emergence herbicides, primarily Gelianthex, should be prioritized in dry years. Further research will focus on analyzing sunflower nectar secretion under different herbicide protection schemes.