By Dr. Eric Reasor
From the February 2023 Subject
The foundation of any turfgrass weed administration program is sustaining an actively rising, wholesome turfgrass stand. Utilizing acceptable cultural practices similar to mowing, fertilization, irrigation, and cultivation for the turfgrass species is one of the simplest ways to assist the garden compete in opposition to weeds. Nevertheless, a number of weeds can persist in even probably the most well-maintained turfgrass. Whereas there’s a rising development to tolerate sure weeds which might be pollinator-friendly (e.g., dandelions) or low-growing nitrogen producers (e.g., microclovers), many consumers nonetheless need a weed-free turfgrass stand. In these eventualities, herbicide use is commonly warranted.
9 of the commonest weeds affecting each warm- and cool-season turfgrass are: crabgrass; yellow and purple nutsedges; kyllinga; dandelion; white clover; oxalis (or yellow wooden sorrel); plantain; prostrate knotweed; and chickweed. Since a few of these weeds have comparable development and management traits, a number of species will be managed with the identical cultural and chemical measures. Due to this fact, it’s necessary to know which weeds are most problematic in your area and develop built-in weed administration packages.
Right here’s an outline of every of the weeds talked about, establish them, and an outline of the pre- and post-emergent herbicides which might be the best in treating them.
In most areas, crabgrass is a Summer time annual grassy weed. It germinates when soil temperatures heat to 55°F for a number of days. It is very important watch temperatures so herbicides will be utilized earlier than the crabgrass emerges since pre-emergent herbicides are the best management. Search for energetic components similar to dithiopyr, indaziflam, pendimethalin, and prodiamine. For maxi- mum efficacy, pre-emergent herbicides should not solely be utilized previous to crabgrass germination, however be adopted by irrigation or rainfall for “activation.”
Put up-emergent herbicides are an amazing software to manage crabgrass that breaks by means of the pre-emergent herbicides. Examples of those herbicides embrace fenoxaprop, fluazifop, pinoxaden, and quinclorac. Put up-emergent herbicides are simplest at early crabgrass development levels with the addition of a sprig adjuvant (e.g., MSO, NIS).
Utilizing the identical herbicide repeatedly will ultimately enable for crabgrass immune to that particular mode of motion to populate. Since there may be solely a small collection of herbicide modes of motion for crabgrass, it’s very important to handle turfgrass correctly by means of cultural practices, weed scouting, and utilizing alternate herbicide modes of motion. It will maximize herbicide efficacy and cut back the chance of herbicide resistance.
Yellow & Purple Nutsedges
Purple nutsedge is extra widespread than yellow in southern areas. Each have triangular-shaped stems and a shiny leaf look. Distinguishing purple nutsedge from yellow nutsedge will be considerably difficult with out the presence of seed heads. Purple nutsedge leaves are abruptly pointed. Yellow nutsedge leaves slowly taper to a degree. Each species have underground tubers and rhizomes that enable them to unfold and return year-to-year. Nutsedges can even unfold by way of seed. Nevertheless, their viability is comparatively low in comparison with different weed species.
Nutsedges desire moist soil circumstances, however can persist in many alternative environments. Cultural management measures might not present acceptable management. Fortuitously, there are a number of herbicide-active components. Some energetic components embrace sulfentrazone, halosulfuron, flazasulfuron, trifloxysulfuron, imazosulfuron, and pyrimisulfan. You’ll want to learn the herbicide label previous to any utility to be used on the precise turfgrass species.
Kyllinga species are weeds within the sedge (Cyperaceae) plant household, however they aren’t nutsedges. There are various totally different kyllinga species that may infest turfgrasses. The most typical and troublesome to manage are inexperienced kyllinga and false-green kyllinga. These perennial weeds can type a dense cover to outcompete turfgrasses year-after-year. Inexperienced and false-green kyllinga usually have a finer leaf texture and a lighter-green shade than nutsedges. They’re additionally prone to have small and burred spherical seed heads on the base of the leaves even when repeatedly mowed. Kyllinga do not need any underground tubers, however they do possess a dense rhizome system. Like nutsedges, kyllinga desire moist soil circumstances but additionally can persist in numerous environmental circumstances.
Mowing peak is among the most necessary components for managing kyllinga in lawns. Growing the mowing peak, particularly with cool-season turfgrass, may give the turfgrass an edge in competitors.
The identical herbicide energetic components used for nutsedge can be utilized for kyllinga. Relying on the turfgrass species, sulfentrazone, halosulfuron, flazasulfuron, trifloxysulfuron, imazosulfuron, and pyrimisulfan herbicides can present kyllinga management.
Frequent dandelion is among the most recognizable weeds on the earth and one of the crucial prevalent in maintained turfgrasses. The long-lasting yellow flower on the tall, hole stalk is definitely identifiable. The yellow flowers then mature into the white “puff balls” or “blow balls” when the seeds develop and are prepared for wind and site visitors dispersal, typically spreading all through giant areas.
Underneath mown circumstances with out the yellow or white flowers, dandelion leaves can be utilized to establish the species. Dandelion leaves are deeply lobed or toothed with an rectangular or spatulate form. The leaves type a rosette which may include many leaves. Dandelions even have a deep taproot and milky sap.
There are quite a few herbicides labeled for dandelion management in turfgrasses. Most of those herbicide energetic components are thought of “broad spectrum” broadleaf herbicides; nonetheless, sure herbicides used for grassy weed management can present dandelion management. Among the most typical energetic components used for dandelion management are 2,4-D, carfentrazone, fluroxypyr, MCPP, MCPA, mesotrione, metsulfuron, penoxsulam, quinclorac, and triclopyr.
Herbicide choice relies on the turfgrass species, web site, and value. Herbicides are additionally much less efficient throughout peak dandelion bloom than they’re pre- and post-bloom. Put up-dandelion bloom will not be one of the best utility timing both because of the seed manufacturing and dispersal of dandelion.
White clover is one other extremely recognizable weed in maintained turfgrasses. Present in warm- and cool-season turfgrasses, white clover is a perennial broadleaf and may tolerate a variety of mowing heights and environments.
The weed will be simply recognized by its leaves and flowers. White clover leaves are a trifoliate leaf association, with three spherical/elliptical leaflets, and sometimes have a white watermark that partially encircles the bottom of every leaflet. White clover produces white flowers on lengthy stems which might be largely current in Spring and Fall. Most energetic white clover development is in Spring and Fall and spreads from stems and stolons that root on the nodes and may type dense mats or clusters.
White clover is a legume, so it may well repair its personal nitrogen and may persist in N-deficient turfgrasses. Growing N fertilization and decreasing soil moisture are two glorious cultural practices for managing white clover. Since white clover is a perennial weed, pre-emergent herbicides
should not readily efficient. Nevertheless, quite a few post-emergent herbicide choices can be found.
Herbicides that include three or extra phenoxy or phenoxy-type energetic components have proven to supply nice management. Some particular energetic components for clover management are carfentrazone, dicamba, fluroxypyr, halauxifen-methyl, MCPP, MCPA, mesotrione, metsulfuron, penoxsulam, quinclorac, and triclopyr. You’ll want to learn all herbicide labels prior to make use of.
Herbicide resistance will not be a widespread downside in white clover; nonetheless, it’s at all times potential for any weed to develop resistance. It’s necessary to use herbicides at labeled charges and alternate modes of motion.
Oxalis is a gaggle of species generally known as woodsorrels. There are a number of woodsorrels problematic in turf, however probably the most prevalent is yellow woodsorrel. It’s a perennial, cool-season weed and grows in a extra upright behavior than white clover.
Yellow woodsorrel weed can look just like clover with a trifoliate leaf association. Nevertheless, it has heart-shaped leaflets as a substitute of spherical. It additionally produces small yellow flowers that distinguish it.
Herbicide management of yellow woodsorrel will be fairly troublesome. Herbicide mixtures that include three or extra phenoxy energetic components won’t present satisfactory management. Further herbicide energetic components to incorporate in purposes to help in herbicide management are as carfentrazone, halauxifen-methyl, mesotrione, metsulfuron, penoxsulam, and sulfentrazone.
Broadleaf and buckhorn plantain are perennial broadleaf weeds present in many sorts of turfgrass. Broadleaf plantain has spherical leaves, whereas buck- horn plantain has slim, lance-shaped leaves. Each species have noticeable parallel leaf veins inflicting them to be simply misidentified with each other. The leaves develop in a rosette with a taproot, and seed heads develop on tall stalks.
Like dandelion, there are quite a few herbicides labeled for plantain management. Among the most typical energetic components used for management are 2,4-D, carfentrazone, dicamba, fluroxypyr, MCPP, MCPA, metsulfuron, penoxsulam, quinclorac, and triclopyr.
There have been documented circumstances of herbicide-resistant buck- horn plantain species attributable to overuse of group 4 herbicides (e.g., 2,4-D, dicamba, and triclopyr). This concern will not be widespread throughout the nation, although it’s important to alternate or mix a number of herbicide modes of motion to mitigate herbicide resistance.
Prostrate knotweed is a Summer time annual broadleaf weed. It germinates in early Spring, usually previous to crabgrass germination. Knot- weed seedlings can resemble grass seedlings quickly after emergence however will develop oval-shaped leaves and type dense mats. It could possibly out- compete turfgrass in compacted soils and is taken into account an indicator of compaction. If knotweed is a persistent downside, contemplate lowering compaction with aeration.
Most pre-emergent herbicides will present acceptable management. Nevertheless, utility timing is necessary as a result of knotweed germinates previous to crabgrass. The energetic components in pre-emergent herbicides that present acceptable management embrace, however should not restricted to, prodiamine, dithiopyr, pendimethalin, indaziflam, and isoxaben.
Put up-emergence knotweed management is usually a lot simpler when herbicides are utilized earlier within the season. The dense cover and thick stems of mature crops could make management troublesome in late Summer time. Typical 3- and 4-way herbicide mixtures containing 2,4- D, dicamba, carfentrazone, fluroxypyr, or triclopyr can present acceptable post-emergent management.
Chickweed is a gaggle of Winter annual weeds present in each cool- and warm-season turf- grasses. Frequent and mouse-ear chickweeds are two which might be usually problematic. They germinate in Fall with cooler soil temperatures. Frequent chickweed has small leaves that come to a degree and small white flowers. Mouse-ear chickweed leaves are additionally small, however are very furry and oval to rectangular formed. Each species can develop upright if not mown however will adapt to mowing by rising prostrate and forming a dense cover.
Chickweeds might be problematic in Spring if not managed in Fall or Winter. The crops might be extra mature and reproducing by way of seed in Spring. Each species are shallow-rooted, so correct irrigation practices are necessary, particularly in Fall and Winter when irrigation wants of turfgrass are a lot much less.
Management of chickweed is easy with acceptable timing. If utilized previous to germination in Fall, pre-emergents that present acceptable management embrace, however aren’t restricted to, prodiamine, dithiopyr, pendimethalin, indaziflam, and isoxaben. If utilizing a post-emergent, most broad spectrum, broadleaf merchandise present acceptable management if utilized previous to Spring seed manufacturing.
Reasor, Ph.D, is Southeast Analysis Scientist with PBI-Gordon Company the place he’s answerable for coordinating all analysis protocols, technical help to cooperators, and product assist for channel companions and end-users in 10 states. Reasor holds a Ph.D. in Turfgrass Weed Science from The College of Tennessee, the place he carried out analysis packages for “off-type” grasses in bermudagrass placing greens, participated in extension actions, and managed weed science analysis packages. He earned his Grasp of Science in Plant Sciences from The College of Tennessee, and a Bachelor of Science in Crop and Soil Environmental Sciences from Virginia Tech College.
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