Even if a field has been designated as a “low-maintenance facility,” minimal weed control efforts are necessary. Without at least a rudimentary strategy for weed control, fields may become unplayable because of a loss of uniformity, creating errant ball bounce and roll and/or a liability due to precarious footing.
Here is our list of the top 10 hard-to-control weed species:
White clover—A member of the legume family, white clover is a cool-season perennial with 1 to 1.5-inch, dark green, trifoliate leaflets. The leaves have prominent, parallel veins and sometimes a white crescent-shaped mark. It has a strong spreading nature, due to the capacity to root at each node. White ball-shaped flowers are held above the leaves when mature. White clover is often indicative of a soil low in nitrogen and may be suppressed by increasing nitrogen fertility. White clover in a field may create a slippery surface, and if allowed to flower, is attractive to bees, increasing the potential for bee stings.
Field bindweed—Field bindweed is a warm-season perennial that grows low to the ground and will tolerate close mowing. Its slender stems are wiry and can grow several feet long. The leaves are generally spade-shaped, 1.5 inches in size and have pointed basal lobes. The root system is extensive. White to pink flowers are conspicuous in summer. Bindweed is primarily a problem in very thin turf subject to excessive wear. It is a prolific seed producer, and seed can remain dormant in the soil for up to 20 years. The long-term seed survival and bountiful seed production make short-term control strategies less than desirable.
Prostrate knotweed—A low-growing annual, prostrate knotweed is especially well adapted to compacted soils. Small, slender, dark green leaves are born on thin, wiry stems that radiate from a central growing point. Prostrate knotweed germinates in cool soils in early spring and tolerates close mowing. While relatively easy to control when young, it is difficult to control when aggressively growing later in the season. Knotweed is a significant problem on lower-maintenance facilities with excessive traffic and resource limitations relative to appropriate aerification equipment.
Wild violets—As cool-season perennials, violets are one of the first plants to flower in spring. They have dark green, heart-shaped leaves and a dense, fibrous root system. The primary reproductive mechanism is via bulbs, and hence the issues with effective control. Once well established, plants produce white, violet or pink flowers that are held above the foliage.
Spotted and prostrate spurge—These summer annuals are similar in appearance. The stems radiate from a taproot, forming a dense mat. Spotted spurge has smooth stems, while prostrate spurge has hairy stems. Leaves are dark green and oblong and may have a reddish splash in the center. The leaves of spotted spurge are somewhat toothed, while prostrate spurge has smooth leaves with some hairs on the underside. All plant parts contain a white milky sap. Compacted, thin turf is an open invitation for spurge invasion.
Ground ivy—Found in either sun or shade, ground ivy is a perennial that spreads rapidly by creeping stems that are four-sided, square and capable of rooting at every node. The leaves are dark green, rounded to scalloped on the edges and deeply veined. In early spring, ground ivy produces tubular or trumpet-shaped flowers that are lavender in color. Ground ivy is an efficient scavenger for nitrogen, resulting in reduced growth of the desirable turf species.
Blackseed plantain—From a central growing point or basal rosette, plantain produces large, dark green, strongly parallel oval leaves and a shallow fibrous root system. Long, rat-tail-like flower stalks extend up to 10 inches long and produce numerous, inconspicuous flowers. As with many of the most problematic species in sports fields, plantain rapidly dominates compacted and thin turf stands.
Black medic—Also a member of the legume family, and sometimes confused with white clover, black medic produces dark green, trifoliate leaves with strong parallel veins. The stems are prostrate, hairy and rise from a central crown area. Flowers are small, bright yellow, compact clusters. Unlike white clover, the flowers are less of an attractant to bees.
Speedwell—There are several types of speedwell, all with small, lobed, numerous leaves and small white or purple flowers. Leaves are in pairs and have scalloped edges. Heart-shaped seedpods grow on the stem below the flowers. Either perennial or annual, speedwell appears in early spring, but can begin greening up in late winter. Most speedwell is characterized by creeping growth with rooting at the nodes. Flowers are very small on short stalks. Speedwell can grow in most any condition, but thrives in dry, sandy and shady areas. Speedwell can become very invasive on sand-based sports fields.
Yellow woodsorrel or oxalis—Often confused with white clover, oxalis has pale green leaves consisting of three leaflets, which are distinctly heart-shaped and appear folded along the midrib. Both annual and perennial types are found. The stems are thin, sparsely hairy and able to root at the nodes. The yellow flowers are small and funnel-shaped. Oxalis has an interesting seed dispersal mechanism, with the capacity to project seed a considerable distance from the mother plant. With this unique property, a small infestation of oxalis can become problematic if not addressed as soon as possible.
Reasons for invasion
Are you sending out an invitation for weeds? Pests and postponed or skipped cultural practices invite the invasion of broadleaf weeds. Many species, including and exclusive of the top 10 already discussed, prosper in thin, highly trafficked and compacted turf, conditions that are frequently the norm in sports fields. Aggressive aerification; proper pest management; and appropriate irrigation, fertility and mowing practices can go a long way in avoiding weed invasion.
Chemical control of broadleaf weeds
So, you’ve done everything you can from a management perspective and you still have broadleaf weeds. Advances in herbicide technology have resulted in the availability of new chemistries with reduced toxicity to nontarget species and increased effectiveness, new formulations and creative new combination products for the turfgrass professional.
Dismiss (sulfentrazone) is effective on a multitude of broadleaf weeds, and weeds susceptible to Dismiss show injury relatively quickly, often within 12 to 24 hours. It acts primarily as a contact herbicide, resulting in regrowth of mature perennials, but is an excellent tank-mix partner with systemic products.
SpeedZone, PowerZone, Surge, Q4-Plus and T-Zone are combination products from PBI-Gordon similar to the its standard Trimec. SpeedZone is what one of our colleagues calls “Trimec with an attitude.” The “attitude” comes from the addition of carfentrazone to the Trimec components. This addition results in faster activity on susceptible species. PowerZone is a non 2-4-D containing alternative to SpeedZone for use in areas where 2,4-D is not desired. Surge contains the components of the Trimec with the addition of sulfentrazone and is formulated to be used safely at higher ambient temperatures. Q4-Plus is the components of Surge with the addition of quinchlorac, increasing the spectrum to include many annual grassy weeds. T-Zone offers the increased efficacy of triclopyr for difficult-to-control broadleaf weeds.
Onetime is a new combination product containing dicamba, MCPP and quinchlorac, offering broad-spectrum broadleaf and annual grass weed control. Tests have shown good-to-excellent activity on ground ivy and dandelion, as well as clover, crabgrass and foxtail. Drive XLR8 is an improved formulation of Drive (quinchlorac) with quicker response and rainfastness in less than one hour.
Tenacity is an herbicide registered for golf courses and sod farms and federally registered for commercial applicator athletic turf use. Tenacity is unique chemistry with unique selectivity. It is safe on all cool-season grasses except creeping bentgrass when used as directed. Trials have shown good-to-excellent control of creeping bentgrass, nimblewill and windmill grass in Kentucky bluegrass, and good-to-excellent control of a laundry list of broadleaf weeds, crabgrass and foxtail. Another unique property of Tenacity is safety at seeding. Applications at planting of Kentucky bluegrass, perennial ryegrass and tall fescue have shown excellent results.