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Horseweed

Description

Horseweed is a winter or summer annual found in waste areas, roadsides and turf. It can vary greatly in height according to the soil it grows in, and the immature rosette looks much different than the mature plant. The erect stem is usually hairy, and is generally branched near the top with small inconspicuous white flowers. The lower leaves are 1 - 4 inches long and toothed, while those scattered along the stem are narrow and smooth. From June to November the plant produces numerous heads of small, inconspicuous white flowers, followed by an abundance of seed.

Cultural Control

Proper turf management is important for biennial broadleaf weed control. Maintain a dense, actively growing turf through proper mowing, fertilizing, and watering practices. Mow at the proper height for your selected adapted turfgrass. Coring and traffic control reduce compaction and encourage desirable turfgrass competition. It is best to control this biennial broadleaf weed in spring or fall, if actively growing at these times.

Chemical Control

Herbicide and Formulation
Amount of Formulation per 1,000 sq ft
Amount of Formulation per Acre
Pounds Active Ingredient per Acre

Preemergence and Postemergence Control

Herbicide and Formulation

mesotrione, MOA 27 (Tenacity) 4 SC

Amount of Formulation per 1,000 sq ft

0.092 to 0.183 fl oz

Amount of Formulation per Acre

4 to 8 fl oz

Pounds Active Ingredient per Acre

0.125 to 0.25

Precaution and Remarks

Use on residential turf, golf courses (not greens) and sod farms for pre- and postemergence weed control. Tolerant turfgrasses include St. Augustinegrass, centipedegrass, tall fescue, fine fescue, Kentucky bluegrass, and perennial ryegrass. Add a nonionic surfactant and repeat application after 2 to 3 weeks for improved postemergence control. Tank mix with Barricade 65 WG for extended preemergence grassy weed control. Can be applied at seeding to all tolerant grasses except fine fescue. After turf germination, wait 4 weeks or until turf has been mowed twice before making a postemergence application. Also controls henbit, chickweed, dandelion, white clover, Florida betony, Florida pusley, ground ivy, oxalis, wild violet, creeping bentgrass, and yellow nutsedge.

Preemergence and Postemergence Control

Herbicide and Formulation

sulfentrazone + prodiamine, MOA 14 + 3 (Echelon 4 SC) 4 SC

Amount of Formulation per 1,000 sq ft

0.184 to 0.826 fl oz

Amount of Formulation per Acre

0.5 to 2.25 pt

Pounds Active Ingredient per Acre

0.25 to 1.125

Precaution and Remarks

For use in residential and institutional lawns, athletic fields, sod farms, golf course fairways and roughs, roadsides, utility right-of-ways, railways, and industrial areas. Apply to turf following a second mowing if a good root system has been established. Apply up to 12 fluid ounces per acre to bentgrass at 0.5 inches or higher, fine fescue, and perennial ryegrass. Apply 18 to 24 fluid ounces per acre to perennial bluegrass, tall fescue, and all warm season grasses except St. Augustinegrass (do not apply) and bermudagrass (apply 18 to 36 fluid ounces per acre). For sod production, apply 6 months after establishment, and do not harvest within 3 months. Do not apply with adjuvants or surfactants. Echelon should not be applied to cool-season turf with N-containing fertilizers unless some short-term discoloration is tolerable.

Presentations

Publications

Species Data

Growth Season/Life Cycle

summer or winter annual weed

Growth Habit

upright; rosette

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Leaflet Number

one

Leaf Margin

smooth or serrated/toothed

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horseweed p1020766
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Leaf Hairs

upper/lower surface

Leaf/Leaflet Shape

linear/oblong/oval/egg-shaped/elliptical; leaves along stem on the mature plant have no petioles

horseweed p1020766
horseweed p1020766
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Leaf Width

<1/2 inch; leaves along stem on the mature plant are about 0.4 inches (10 mm) wide

Leaf Arrangement

alternate; whorled or basal rosette

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Flower Color

white