How global climate change makes it harder to farm: Higher CO2 levels, warmer temperatures may spur glyphosate resistance in some weeds

| | February 19, 2019
roundup spray
Image: Grant Gerlock/Harvest Public Media
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Herbicides are the most commonly used means of controlling weeds. Recently, there has been growing concern over the potential impacts of global climate change, specifically, increasing temperatures and elevated carbon dioxide (CO2) concentrations, on the sensitivity of weeds to herbicides.

Here, glyphosate response of [the weed species] Conyza canadensis and Chenopodium album was evaluated under different environmental conditions. Reduced glyphosate sensitivity was observed in both species in response to increased temperature, elevated COlevel, and the combination of both factors. Increased temperature had greater effect on plant survival than elevated CO2 level.

Glyphosate was [previously] found to be less effective under either high temperatures [e.g. in Conyza canadensis] or elevated carbon dioxide (CO2) levels [e.g. in Chenopodium albumCirsium arvense and Glycine max] but no studies, to our knowledge, have examined the joint effects of both increased temperature and elevated CO2 level on plant response to glyphosate.

Plant sensitivity to glyphosate was reduced under high temperatures and elevated CO2 levels. For both species [of weeds in the study] and all populations, plant survival was highest under the combined high temperature and elevated CO2 (HT/ECO2) treatment.

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Taken together, the results of our study clearly indicate that the control of two major weeds in California agriculture by glyphosate could be reduced under the projected changes in climatic conditions. Compared to current conditions, both C. canadensis and C. album plants were less sensitive to glyphosate under the higher temperatures, elevated COlevels and the combination of both environmental conditions, which are predicted for the future.

In conclusion, we have shown that glyphosate-treated plants grown under increased temperature and elevated CO2 level exhibit reduced glyphosate sensitivity. Thus, the continued overreliance on glyphosate for weed control under changing climatic conditions may result in more weed control failures.

Read full, original article: Increased temperatures and elevated CO2 levels reduce the sensitivity of Conyza canadensis and Chenopodium album to glyphosate

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