Climate Change & Herbicide Efficacy

Follow the links below for tables that detail changes in efficacy of common herbicides on specific weed species based on increasing temperatures, higher CO2 levels, higher humidity, and drought:

Weeds and Climate Change

The climate is changing in New York State, with wetter winters and springs, dryer summers and falls, and increasing temperatures overall. Farmers are experiencing more erratic spring weather and shorter windows for management actions, including appropriate weather conditions for weed management. Weeds  are becoming more or less competitive as conditions change and we are seeing new weed species arriving from the south. Herbicide efficacy is also changing, with some herbicides becoming more effective under hot/dry conditions and some less effective. Understanding these trends help agronomic producers refine weed management tactics for whatever weather comes our way. Our research review has focused on three areas – herbicide efficacy under climate change, anticipated changes in weed competition, and range shifting species.

 

New York State Weather Trends

New York State is already warmer than the last century, experiencing warmer winters and more heat waves in the summer. Farmers are seeing more heavy precipitation events, especially in the winter and spring. Between now and 2050, the state is expected to see more summer drought periods and extreme rainfall events. The growing season in New York State is about a week longer than it was in the previous century, with later first frost dates and more variable last frost dates. In 2023, an updated USDA Plant Hardiness Zone Map officially shifted growing zones in many parts of New York.

 

Herbicide Efficacy in a Changing Climate

Carbon dioxide (CO2), high temperatures, and drought conditions all impact herbicide efficacy, but herbicide chemistries respond differently to these variables. The target weed specie also matters; certain weeds become less susceptible to some herbicides and others more susceptible. When utilizing herbicides in a hot/dry or cool/wet seasons, good management practices become increasingly important. These best practices include correct weed species ID, understanding which herbicides work best in which  weather conditions, and using the right surfactant and the right nozzle for your application. 

 

Changes in Weed Competition with Crops

Higher CO2 levels help some plants grow more quickly, while higher temperatures affect (benefit) the growth of both weeds and crops. Some weeds will be more competitive in hot, dry summers, others will overwinter more successfully in warmer, wetter winters. As New York State’s climate becomes more like the mid-Atlantic states, some weeds may become better controlled by seed predators or other insects that don’t currently overwinter in New York.

 

Range Shifting Weed Species

Weeds that are currently problematic in mid-Atlantic states are likely to arrive in New York, or to become more difficult to control if they are already here. Some species to watch are johnsongrass (Sorghum halepense), burcucumber (Sicyos angulatus), and ivy leaf and pitted morning-glory (Sicyos angulatus and S.lacunos).

Review our information here to find how photosynthetic pathway affects a weed’s response to climate change, specific recommendations for herbicides in hot/dry weather, and what we do and don’t know about changing competitiveness and new weeds likely to come to New York State.

 

This research was supported by the intramural research program of the U.S. Department of Agriculture, National Institute of Food and Agriculture, Multistate #2021-22-183. The findings and conclusions in this preliminary publication have not been formally disseminated by the U.S. Department of Agriculture and should not be construed to represent any agency determination or policy.

References

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  2. Fernando, N., Manalil, S., Florentine, S. K., Chauhan, B. S., & Seneweera, S. (2016). Glyphosate Resistance of C3 and C4 Weeds under Rising Atmospheric CO2. Frontiers in plant science, 7, 910.
  3. Jabran, K., & Doğan, M. N. (2018). High carbon dioxide concentration and elevated temperature impact the growth of weeds but do not change the efficacy of glyphosate. Pest management science, 74(3), 766–771. 
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