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Weed Avengers: How to tackle turf foes

April 14, 2021 -  By

Dallisgrass, clover, ground ivy and wild violet are some of the toughest weeds lawn care operators will face. To help tame and conquer these turf issues, Lane Tredway, Ph.D., technical services manager for Syngenta; Eric Reasor, Ph.D., Southeast research scientist with PBI-Gordon; Ian Rodriguez, Ph.D., technical service manager with Quali-Pro; Rod Marquardt, Nufarm’s warm-season national account manager; and Jamie Heydinger, Nufarm’s cool-season national account manager, share identification, management and control tips.

Dallisgrass is a coarse-textured perennial grass and grows in clusters. (Photo courtesy of PBI Gordon Corp.)

Dallisgrass is a coarse-textured perennial grass and grows in clusters. (Photo courtesy of PBI-Gordon Corp.)

Dallisgrass

What to look for:

⦁ Dallisgrass is a coarse-textured perennial grass with a bunch-type growth habit. Leaves are rolled in the bud with rough edges and a prominent midvein. It produces conspicuous seedheads from midsummer to fall, along with alternating branches that look like caterpillars suspended from the stalk. –LT

⦁ It has a wide leaf blade that tapers to a point and no hairs on the leaf margin. It spreads via rhizomes and seeds but tends to grow in clusters. –ER

How to control it:

⦁ The preemergent approach is best. Any postemergent program will take at least two applications and probably more. Consider wick-applied nonselective options for small areas. –IR

⦁ Dallisgrass is quite sensitive to postemergent herbicides in the fall or spring. Postemergent options include trifloxysulfuron-sodium or pinoxaden herbicides in Bermudagrass or zoysiagrass turf or fluazifop-P-butyl in tall fescue. –LT

⦁ Consider tank mixing multiple herbicide active ingredients for increased control and reduced turfgrass injury potential. –ER

Keep in mind:

⦁ Once established, dallisgrass can be resilient to the effects of herbicides and may take several years to bring under control. –LT

⦁ It loves nitrogen fertilizer and grows twice as fast as desirable grass. –RM

⦁ Interseeding cool-season lawns in fall can help decrease the dallisgrass population over time. –ER

White clover is the most common type of clover that can be found in turfgrass. (Photo courtesy of PBI-Gordon Corp.)

White clover is the most common type of clover that can be found in turfgrass. (Photo courtesy of PBI-Gordon Corp.)

Clover

What to look for:

⦁ There are many species of clover, but white clover is the most common in turfgrass. Each leaf has three leaflets. White clover has a small white semicircle at the base of each leaflet. –ER

How to control it:

⦁ White clover is a perennial plant; therefore, postemergent herbicides are most effective. There are countless selective herbicide options for effective clover control in any turfgrass species. Typical herbicide modes of action used for selective control are synthetic auxins, ALS inhibitors, HPPD inhibitors and PPO inhibitors. –ER

⦁ Mesotrione provides effective pre-and postemergent control of white clover. It can be applied at the time of seeding tolerant turf species to prevent clover establishment. Trifloxysulfuron-sodium and two- and three-way mixtures containing 2,4-D, dicamba, triclopyr or fluroxypyr are also highly effective options for clover control. Repeat applications are often needed to control well-established clover infestations. –LT

Keep in mind:

⦁ White clover can tolerate low mowing heights, and their dense canopies can shade the desired turfgrass. –ER

⦁ White clover has a competitive advantage in poor fertility situations. –IR

⦁ Healthy turf is the best defense. –JH

Ground ivy features square stems and smells like mint if crushed. (Photo courtesy of PBI-Gordon.)

Ground ivy features square stems and smells like mint if crushed. (Photo courtesy of PBI-Gordon Corp.)

Ground Ivy

What to look for:

⦁ Ground ivy is a creeping perennial with square stems, opposite leaves (leaves in pairs from the stem), blue/purple flowers. It smells like mint if crushed. –IR

⦁ Ground ivy spreads by stolons and can form dense canopies that shade the turf (similar to clovers). It prefers wet and shaded areas. –ER

How to control it:

⦁ Mesotrione or trifloxysulfuron-sodium are effective options for postemergent control intolerant grass species. Herbicide mixtures containing 2,4-D, dicamba, triclopyr or fluroxypyr are also effective options. Repeat applications are often needed to achieve acceptable control. –LT

⦁ Consider using ester formulations. Fall applications work best, and two or more applications may be required. –RM

⦁ Ground ivy is a perennial plant; therefore, postemergent herbicides are most effective. –ER

Keep in mind:

⦁ Ground ivy is most aggressive and difficult to control in shaded areas. Plant shade-tolerant turfgrasses and adjust mowing and fertility practices accordingly to improve turf competitiveness. –LT

⦁ Ground ivy can be an indicator of acidic soils. Consider a soil analysis to determine if lime applications are required. Increase the amount of light getting to the turfgrass and correct any drainage issues. –ER

While violets are used commonly as groundcover they can escape to invade turfgrass areas. (Photo courtesy of PBI-Gordon Corp.)

While violets are used commonly as groundcover they can escape to invade turfgrass areas. (Photo courtesy of PBI-Gordon Corp.)

Wild violet

What to look for:

⦁ Violets are a group of perennial or winter annual plants commonly used as groundcover but can escape to invade turfgrass areas. They have bunch-type or mat-forming growth habits. –LT

⦁ It has a heart-shaped leaf with rounded teeth. –IR

⦁ Plants spread by large, branching rhizomes and prefer shaded conditions. Flowers can be purple, blue or even white. –ER

⦁ Wild violets have a dense, fibrous root system. Their waxy leaf surface makes it hard for herbicides to penetrate. –JH

How to control it:

⦁ Ester and triclopyr-based products applied early or late in the season have shown best results. More than one application is usually needed. – JH

⦁Wild violets are perennial; therefore,post-emergent herbicides are most effective. Selective herbicide control can be difficult; however, certain active ingredients are better than others. Examples of those are triclopyr, fluroxypyrand metsulfuron. –ER

Keep in mind:

⦁ Wild violet is most aggressive in wet or shady locations. Improving soil drainage, avoiding overirrigation, improving sunlight penetration and using shade-tolerant turf species where appropriate can help slow its spread. –LT

⦁ Increasing the turfgrass mowing height can negate some of the shade effects caused by wild violet. –ER

Christina Herrick

About the Author:

Christina Herrick is the editor of Landscape Management magazine. Known for her immersive approach to travel from coast to coast in her previous stint as senior editor of American Fruit Grower Magazine, she uses social media (Twitter/Instagram @EditorHerrick) to share her experiences on the road with her audience. Herrick has a degree in journalism from Ohio Northern University and has been in B2B publishing for seven years. She can be reached at cherrick@northcoastmedia.net.

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