Weeds & Climate Change

New York’s climate is changing, with wetter winters and springs, dryer summers and falls, and increasing temperatures overall. Farmers are experiencing more erratic spring weather featuring shorter windows for management actions, including appropriate weather for weed management.

Weeds are also changing, becoming more or less competitive with changing conditions, and new 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 can help producers plan weed management strategies to cope with variable weather conditions, and help refine management tactics for whatever the weather comes our way.

New York Weather Trends

New York is already warmer than it was in the last century, with warmer winters and more frequent and longer lasting heat waves in the summer. The state is experiencing more heavy precipitation events, especially in the winter and spring. Between now and 2050, the state is expected to see an increase in summer drought periods and extreme rainfall events. First frost dates are getting later, while spring last frost dates are becoming more variable. New York’s growing season is about a week longer than it was in the previous century. In 2023, an updated growing zone map officially shifted the USDA growing zones in many parts of New York.

Herbicide Efficacy in a Changing Climate

Herbicide efficacy is expected to change under future climate conditions. Carbon dioxide (CO2), high temperatures, and drought conditions all impact herbicide efficacy, but herbicide chemistries respond differently to these variables. The weed species being controlled also affects efficacy, with some plants becoming more able to survive treatment with some herbicides and others becoming more susceptible. When selecting herbicides for use in a hot/dry or cool/wet season, it’s important to know your weed species, understand which herbicides will work better in your weather conditions, and use the right surfactant and the right nozzle for application. Good management becomes increasingly important.

Changes in Weed Competition with Crops

Higher CO2 levels help some plants grow more quickly, while high temperatures affect the growth of both weeds and crops. Some weeds will be more competitive in hot, dry summers, while others will overwinter more successfully in warmer, wetter winters. As our 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 burcucumber and ivyleaf and pitted morning-glory.

Stay tuned for more details on how photosynthetic pathway affects a weed’s response to climate change, herbicide efficacy for New York labeled herbicides, and what we do and don’t know about changing competitiveness and new weeds likely to come to New York.

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