Common and western ragweed (Ambrosia artemisiifolia and cumanensis) emerge in the spring and set seed in late summer/fall.
Common ragweed grows 1 to 4 feet tall and has many lobed leaves. Lanceleaf ragweed grows 1 to 4 feet tall with rough leaves bearing two sharp teeth on a broad base.
Western ragweed is an erect, bushy plant growing 1 to 2 feet tall. Leaves are silvery-green and usually covered with fine hairs. A deep, extensive root structure makes it extremely drought-hardy.
Common ragweed is native to North America and can be found in every state in the United States except for Alaska. Western ragweed can be found through most of the United States, but heavy infestations are found mainly in the Southwest. Ragweed thrives in disturbed soils and problems are greater in pastures that fail to maintain competition from a full leaf canopy of grass during late May through late June.
If weather or heavy grazing has left your forage stands weak, scout for tiny plants or seedlings underneath the grass during the early spring. Heavy grazing or haying during this time opens the grass sward, letting seedlings and small plants grow rapidly.
Whether it’s annual or perennial, the ragweed in your pastures can be kept in check with a good, timely pasture management program. However, common ragweed is controlled more easily with grazing management or herbicides than western ragweed. Western ragweed can produce 200 new shoots off a single plant, making infestations easier and may require more than one treatment.
For common ragweed, apply 12 to 16 fluid ounces of DuraCor per acre or 2 to 2.5 ounces per acre of Chaparral™ herbicide. Use lower rates when weeds are small and actively growing. Increase rate as season progresses and plants become more mature or for maximum residual control.
Treat western ragweed with 12 to 16 fluid ounces of DuraCor per acre or 2.5 to 3.3 ounces of Chaparral per acre. For nonresidual weed control, apply 1 to 1.5 pints per acre of PastureGard® HL herbicide. Apply in the spring to actively growing plants prior to flowering, usually from spring to early summer.
Label precautions apply to forage treated with Chaparral or DuraCor and to manure and urine from animals that have consumed treated forage. Consult the label for full details.
Chaparral and DuraCor are not registered for sale or use in all states. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state Always read and follow label directions.