Glyphosate hormesis in broad-leaved weeds: a challenge for weed management

ABSTRACT

Little is known of glyphosate-induced hormesis in weeds and how this might influence weed management. To test the hormetic effect of low doses of glyphosate on broad-leaved weeds, two experiments were conducted, in the laboratory and the screenhouse. The hormetic effects of glyphosate solution in growth media (0, 65, 130, 250, and 500 g acid equivalent (a.e) ha⁻¹) and foliar spray (0, 4, 8, 16, 32, and 64 g a.e. ha⁻¹) were tested on four broad-leaved weeds (Coronopus didymus, Chenopodium album, Rumex dentatus, and Lathyrus aphaca). Glyphosate solution in the range 65–250 g a.e. ha⁻¹ stimulated the germination and seedling growth of all tested weeds. However, at 500 g a.e. ha⁻¹ inhibition of germination and growth was observed. Foliarly applied glyphosate in the range 4–32 g a.e. ha⁻¹ increased root and shoot length, dry biomass, and seed production ability of all four weeds species; however, the stimulatory response was species dependent. These results indicate that glyphosate hormesis could play a significant role in altering crop/weed competition and might influence weed management.

KEYWORDS:

• Herbicide hormesis
• weed growth stimulation
• reproductive potential
• resistance evolution

Disclosure statement

No potential conflict of interest was reported by the authors.