Auxin-mimic herbicides dilema: Their benefits and limitations

Auxinic herbicides have revolutionized weed control since their introduction in agriculture in 1945. In recent years, auxinic herbicides have become essential and cost-effective weed management tools to control glyphosate-resistant and other difficult-to-control weeds in soybean and cotton. The recent commercialization of auxinic-resistant crops (ARC) (i.e., soybean and cotton) allows preemergent and in-season post-emergent applications of auxinic herbicides. However, the off-target movement of auxinic herbicides has been a recurring problem, threatening the livelihood of growers producing sensitive plants such as cucurbits, tomatoes, and grapevines. It is challenging to pinpoint the exact source of the drift and assess the short and long-term impacts of auxinic herbicides drift to sensitive surrounding vegetation. In this context, we provide an overview on the relative sensitivity of several important crops to very low doses of the auxinic herbicides dicamba and 2,4-D.

Given the wide range of effects triggered by auxinic herbicides in plant metabolism, sensitive crops are highly variable in their responses to sublethal doses; however, there is a consensus that crop symptomatology is not always predictive of yield loss or growth penalties. These studies demonstrate the difficulty of observing patterns that indicate when management decisions should be made after a suspected off-target movement event.

Several crops are sensitive to auxinic herbicides, which can cause damage and may affect crop yield. Therefore, there is a need to develop a low-cost and consistent diagnosis tool to detect very low doses of auxinic herbicides in sensitive species in the field, thus the losses of produced crop due to contamination with the auxinic herbicides in concentrations above the limit for consumption could be rapidly detected. This review demonstrates that ARC is sustainable in weed management only if application practices are improved to minimize unintended off-target damage. © 2025 Society of Chemical Industry.