Community Agriculture Alliance: Managing noxious weeds in drought
For Steamboat Pilot & Today
Spring has arrived, and with it comes greening meadows, budding trees and shrubs and the emergence of our early season weeds. Though recent moisture has left us all feeling optimistic for a wet spring, the U.S. Drought Monitor is still showing Routt County in extreme and exceptional drought. It is encouraged that land managers, agricultural producers and gardeners consider mitigation for drought in regards to their weed control efforts when planning for their 2021 growing season.
Like our native and desired vegetation, noxious weeds are also hindered by drought. However, most noxious weeds do not have as many additional stressors to deal with, such as insects, disease and browsing by livestock and wildlife. Noxious weeds have adapted to grow faster, disperse prolific amounts of seed and mine deeper for water and nutrients, allowing them to easily out-compete neighboring vegetation. There are some weeds notorious for thriving in drought conditions, and those include kochia, field bindweed and Russian thistle. If these species are located on your property, be sure to manage them to prevent their spread and be on the lookout for their establishment in new locations.
High temperatures and low moisture cause plants to initiate biological drought defenses in order to reduce water loss and ensure their continued survival and seed set. Such defenses include thicker cuticles or leaf hairs, reduced leaf surfaces, stunted growth, delayed or staggered germination of seeds and closed stomata resulting in reduced metabolism in plants. All of these defenses alter our window for treatment and hinder the effectiveness of systemic herbicides. Systemic herbicides are often the most economical and feasible control option for large infestations and are required for perennial noxious weeds that develop extensive and deep root systems that cannot be controlled by mechanical, chemical, biological or cultural means alone. These deep rooted perennials include Whitetop, Toadflaxes, Leafy spurge and Canada thistle, just to name a few. Oftentimes, the part of the plant we see above ground is only the tip of the iceberg.
However, there are some tools in our toolbox to help us get control of these weeds despite their drought defenses.
• Scout early and more often for weeds during drought, knowing that staggered germination will be challenging and most likely require additional follow-up spot treatments.
• Promote growth and competition of desired and native vegetation.
• Control weeds while they are young and actively growing. Plan chemical treatments after moisture events when plants ramp up their metabolism and restore active growth.
• Use an adjuvant in chemical solutions to improve spray coverage, slow evaporation and better penetrate leaf cuticles.
• Use the higher end of suggested label rates in drought years to ensure plant mortality and reduce chances of resistance. It is important to calibrate all spray equipment to ensure you are not over applying. Remember, the label is the law.
• Integrated weed management approaches should always be performed but especially during drought years when herbicide effectiveness can be significantly hindered.
Noxious weeds know no bounds and have significant negative impacts on agriculture, recreation, wildlife and native ecosystems. It takes everyone doing their part to prevent their spread. For more information, contact the Routt County Noxious Weed Program by emailing firstname.lastname@example.org or call 970-870-5246 or CSU/Routt County Extension at 970-879-0825 or email@example.com.
Tiffany Carlson is with the Routt County Weed Department.
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