Chemical control of Sosnowsky's hogweed (Heracleum sosnowskyi Manden.) in Ukraine

Sosnowsky's hogweed (Heracleum sosnowskyi Manden.) is known as an invasive, ineligible, harmful to human health, and hardly controlled plant. The purpose of this study was to evaluate the efficiency of chemical control when different herbicides were applied at various development stages of H. sosnowskyi plants. The experiment was carried out in Ukraine over the period of 2013-2020. Two field experiments on the first-year and second-year H. sosnowskyi plants were conducted. All the selected herbicides were applied at the rates registered in Ukraine. The first-year plants ofH. sosnowskyi were the most sensitive to the herbicides at the cotyledon stage - the efficacy of herbicides ranged from 97.3% to 100%. Postponing the herbicide application up to a six-leaf stage, the efficacy ranged from 43.2% to 60.7%. The most effective were the following herbicides: Task Extra 66.5 WG (rimsulfuron 23 g kg-1, nicosulfuron 92 g kg-1, dicamba 550 g kg-1) + Trend 90 at application rates of 385 g ha-1 + 0.2 L ha-1 and MaisTer Power OD (foramsulfuron 31.5 g L-1 + iodosulfuron 1.0 g L-1 + thiencarbazone-methyl 10 g L-1 + cyprosulfamide (antidote) 15 g L-1) at an application rate of 1.5 L ha-1. The second-year plants ofH. sosnowskyi were effectively controlled by the following herbicides: Elumis 105 OD (mesotrione 75 g L-1, nicosulfuron 30 g L-1) at an application rate of 2.0 L ha-1 and the tank composition Elumis 105 OD + Roundup Max (glyphosate potassium salt 551 g L-1) at application rates of 2.0 + 6.0 L ha-1.The results of the experiment clearly showed that the sensitivity of H. sosnowskyi plants to herbicides decreased with increasing the stages of plant development of the first-year of H. sosnowskyi. The results suggest that the combination of mesotrione, nicosulfuron, and glyphosate might be a suitable solution for the chemical control of second-year plants of Sosnowsky's hogweed.