Can herbicides of different mode of action cause injury symptoms in non-herbicide-tolerant young soybean due to simulated drift?

Accidental herbicide drift onto neighboring crops, such as soybeans, can seriously harm non-target plants, affecting their growth and productivity. This study examined the impact of simulated drift from ten different herbicides (2,4-D, dicamba, glyphosate, saflufenacil, oxyfluorfen, hexazinone, diuron, diquat, nicosulfuron, and isoxaflutole) on young soybean plants. These herbicides were applied at three simulated drift levels (1/4, 1/16, and 1/32) equivalent to recommended commercial doses, and the resulting symptoms were carefully evaluated. Simulated drift caused distinctive symptoms, including chlorosis, twisting, necrosis, and growth abnormalities, varying depending on each herbicide's mode of action. Dicamba proved more toxic than 2,4-D, and symptom severity increased with drift proportion, with all herbicides causing over 30% injury at the 1/16 proportion. Notably, 2,4-D, dicamba, glyphosate, hexazinone, and diquat exceeded the half-maximal inhibitory concentration (IC₅₀) value, significantly reducing total biomass. Dicamba consistently caused 50% injury at all proportions, while hexazinone, at the highest dose proportion, led to plant mortality. Dicamba also had biomass accumulation beyond the growth reduction (GR₅₀), whereas hexazinone exhibited less than 10% accumulation due to its capacity to induce plant mortality. This study emphasizes the importance of understanding herbicide drift effects on non-target crops for more effective and safe weed management strategies.