Understanding herbicide hormesis: Evaluating its positive and negative aspects with emphasis on glyphosate

Authors: DUKE, STEPHEN - University Of Mississippi; BELZ, REGINA - University Of Hohenheim; CARBONARI, CAIO - Sao Paulo State University (UNESP); VELINI, EDIVALDO - Sao Paulo State University (UNESP)

Submitted to: Advances in Weed Science
Publication Type: Review Article
Publication Acceptance Date: 2/3/2025
Publication Date: 3/14/2025
Citation: Duke, S.O., Belz, R.G., Carbonari, C.A., Velini, E.D. 2025. Understanding herbicide hormesis: Evaluating its positive and negative aspects with emphasis on glyphosate. Advances in Weed Science. 2025(43):e020250104. https://doi.org/10.51694/AdvWeedSci/2025;43:00006.
DOI: https://doi.org/10.51694/AdvWeedSci/2025;43:00006

Interpretive Summary: Research on the uses of herbicide hormesis to improve crop yield and the role of herbicide hormesis in weed management has greatly increased in recent years. The use of herbicide hormesis to improve crop quality and yield has been hampered by erratic results and difficulty in choosing a dose that will provide reliable hormesis in the field. A sequential application of low glyphosate doses in the form of a seed treatment followed by a low dose after seedling emergence has been recently shown to provide more predictable hormesis in the field, resulting in significant increases in crop yield. However, herbicide hormesis can hamper weed management with herbicides in two ways. Recommended herbicide doses that overlap the hormetic dose range of some weeds can give them a competitive advantage. This is probably rare, but hormesis for weed subpopulations that are more tolerant/resistant than most of the plants in a weed population can accelerate the selection for and spread of herbicide resistance, a potentially more common phenomenon. The molecular mechanism(s) of herbicide hormesis is/are still unknown, other than mild stress triggering overcompensation, resulting in enhanced growth and reproductive processes. Glyphosate hormesis appears to be more consistent and pronounced than that with other herbicides. This may be due to large number of essential compounds produced by the shikimic pathway, compared to other herbicides and/or to its highly systemic mode of action.

Technical Abstract: Research on the uses of herbicide hormesis to improve crop yield and the role of herbicide hormesis in weed management has greatly increased in recent years. The use of herbicide hormesis to improve crop quality and yield has been hampered by erratic results and difficulty in choosing a dose that will provide reliable hormesis in the field. A sequential application of low glyphosate doses in the form of a seed treatment followed by a low dose after seedling emergence has been recently shown to provide more predictable hormesis in the field, resulting in significant increases in crop yield. However, herbicide hormesis can hamper weed management with herbicides in two ways. Recommended herbicide doses that overlap the hormetic dose range of some weeds can give them a competitive advantage. This is probably rare, but hormesis for weed subpopulations that are more tolerant/resistant than most of the plants in a weed population can accelerate the selection for and spread of herbicide resistance, a potentially more common phenomenon. The molecular mechanism(s) of herbicide hormesis is/are still unknown, other than mild stress triggering overcompensation, resulting in enhanced growth and reproductive processes. Glyphosate hormesis appears to be more consistent and pronounced than that with other herbicides. This may be due to large number of essential compounds produced by the shikimic pathway, compared to other herbicides and/or to its highly systemic mode of action.