The Nightmare Weeds of 2025 Our annual weed survey reveals familiar names — and some new arrivals.
THISTLES > One of the more aggravating weed families, thistles come in a variety of species. Of the four main types that cause the most concern for U.S. growers and ranchers, musk, bull and Scotch thistles are all biennials, while Canada thistle is a hardy perennial. Thistles can be easily identified by the spiny leaves and round, purple or pink flowers that resemble pincushions. Not only do these prickly pests compete with forage grasses for moisture and nutrients but also they, in effect, shrink pastures because cattle avoid grazing near them. Treatment > For biennial thistles, apply NovaGraz™ herbicide at 24 fluid ounces per acre plus 1% MSO v/v. For bull and musk thistle, apply 12 to 16 fluid ounces of DuraCor® herbicide per acre or 1¼ pints per acre of GrazonPD3™ herbicide at the rosette stage, or apply 2 to 2⅔ pints per acre of GrazonPD3 from bolting to bud stage. For Scotch thistle, apply 16 fluid ounces of DuraCor per acre or 1 ¼ pints per acre of GrazonPD3 at the rosette stage, or 2 to 2⅔ pints per acre of GrazonPD3 from bolting to bud stage. For Canada thistle, apply 16 fluid ounces of DuraCor per acre or 2½ pints per acre of GrazonPD3 prior to bud stage. SILVERLEAF NIGHTSHADE > Silverleaf nightshade has foliage with a gray or silvery appearance with violet, light blue or white flowers and is 1 to 3 feet tall. Stems are sparsely covered with short, yellow thorns. Leaves and stems have a dense silvery covering of hair. Treatment > Apply 16 fluid ounces of DuraCor® herbicide per acre or 1¼ pints per acre of GrazonPD3 herbicide when plants are 4 to 6 inches tall, or 2 to 2⅓ pints per acre of GrazonPD3 when flowering or for longer residual control of later-emerging plants. Re-treatment is necessary for total control. HORSEWEED/MARESTAIL > Horseweed, also known as marestail, is a tall-growing winter or summer annual. Its’ stem usually has short bristly white hairs with many alternate and lance-shaped leaves. It blooms June to August with numerous tiny, inconspicuous flowers. Treatment > Apply 24 fluid ounces per acre of NovaGraz™ herbicide plus 1% MSO v/v, or 16 fluid ounces of DuraCor® herbicide per acre, or ⅔ to 1¼ pints per acre of GrazonPD3™ herbicide when weeds are less than 3 inches tall, or 2 to 2⅔ pints per acre of GrazonPD3 when plants are taller than 3 inches through early flowering stage. WESTERN RAGWEED > Western ragweed can be found throughout much of the United States but is particularly prevalent in the Southwest. Western ragweed grows into a bushy plant, 1 to 2 feet tall, with silvery-green leaves that may be covered with fine hairs. This drought-hardy weed is a prolific reproducer, so multiple treatments may be necessary for complete control. Treatment > Apply 24 fluid ounces per acre of NovaGraz™ herbicide plus 1% MSO v/v, or 16 fluid ounces of DuraCor® herbicide per acre, or ⅔ to 1¼ pints per acre of GrazonPD3™ herbicide when weeds are less than 3 inches tall, or 5 pints of GrazonPD3 herbicide per acre per 100 gallons of spray. For best control, apply to weeds that are actively growing but prior to flowering. LEAFY SPURGE > This deep-rooted perennial can quickly become established and crowd out desirable vegetation, making prevention and early treatment the most effective courses of action. Leafy spurge can be identified by its smooth, clustered stems, narrow leaves, with flowers enclosed by heart-shaped bracts. Treatment > Apply GrazonPD3™ at 1.2 to 2.5 quarts per acre broadcast by ground or air, applied at the true flower stage or during fall regrowth. Or, apply 2 pints of Tordon® 22K herbicide per acre or tank mix of 1.5 to 2 pints of Tordon 22K plus 1 quart of 2,4-D amine per acre. Apply at the true flower growth stage or during fall regrowth. Reapply Tordon 22K when level of control drops below 80%. If weedy worries are keeping you awake at night, we have good news. First, you’re not alone. Based on the survey results of Corteva Agriscience Range & Pasture Specialists, ranchers across the country are fighting many of the same problems. Second, Corteva Agriscience™ has a solution for just about any weed that may be causing you grief. Ready to get back to sleep? Find the solution to your nightmare weeds below.
™ ® Trademarks of Corteva Agriscience and its affiliated companies. GrazonPD3 ™ and Tordon ® 22K are Restricted Use Pesticides. White clover and Annual lespedeza exhibit some initial injury (such as lodging and loss of vigor) with NovaGraz application but recover. NovaGraz™ is not registered for sale or use in all states. Under normal field conditions, DuraCor ® is nonvolatile. DuraCor has no grazing or haying restrictions for any class of livestock, including lactating dairy cows, horses (including lactating mares) and meat animals prior to slaughter. Label precautions apply to forage treated with DuraCor and to manure and urine from animals that have consumed treated forage. Not all products are registered for sale or use in all states. GrazonPD3 is not for sale, distribution or use in Nassau and Suffolk counties in New York state. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. Consult the label for
full details. Always read and follow label directions. ©2025 Corteva. 06
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