Weed Control – Page 3 – Center for Urban Agriculture

Postemergence Bermudagrass Control in Turf

November 30, 2015July 23, 2014 by Willie Chance

An excerpt taken from the publication Bermudagrass Control in Southern Lawns by Patrick McCullough, UGA Extension Weed Specialist

Find the entire publication here

Bermudagrass plants. (Photo - P. McCullough.) — Bermudagrass plants. (Photo – P. McCullough.)

Postemergence Herbicide Control

Postemergence herbicides may be applied to suppress bermudagrass populations and reduce competition with desirable turfgrasses. Repeat applications of selective herbicides are needed for best results but may be injurious to the desirable species. Furthermore, tolerance to herbicides may vary by turfgrass cultivar and end-users should consult with local Extension specialists for application rates and recommendations.

Bermudagrass Control in Centipedegrass

Centipedegrass is a popular low-maintenance lawn species in Georgia. Centipedegrass generally has slower growth than bermudagrass with less potential for competition during the summer. Clethodim (Envoy, others) and sethoxydim (Segment, others) are cyclohexenadione herbicides that inhibit lipid synthesis in grassy weeds. Sensitive species exhibit leaf injury with reddish discoloration before significant necrosis.

Bermudagrass is sensitive to both clethodim and sethoxydim and repeat applications may suppress populations in centipedegrass. Turf managers should schedule applications approximately every three weeks during active growth. For best results, add a nonionic surfactant at 0.25% v/v with clethodim to enhance spray retention and apply no sooner than three weeks after spring green up. Certain sethoxydim products (e.g., Segment) may have a built-in adjuvant already mixed in the formulation and the addition of a surfactant is not required. For both herbicides, turf managers should avoid mowing one week before or after treatment.

Bermudagrass Control in St. Augustinegrass

St. Augustinegrass is a major warm-season turfgrass used for lawns in southern Georgia. St. Augustinegrass has desirable heat and drought tolerance but is sensitive to many herbicides. Selective herbicides for controlling grassy weeds, such as crabgrass and goosegrass, are limited in St. Augustinegrass lawns. Bermudagrass infestations are also difficult to manage.

St. Augustinegrass has good tolerance to ethofumesate (PoaConstrictor, Prograss), which may be used in combination with atrazine to control bermudagrass. Ethofumesate is an unclassified herbicide that has postemergence activity for grassy and broadleaf weed control in nonresidential St. Augustinegrass and cool-season grasses. Ethofumesate has several toxic effects in susceptible species, such as bermudagrass, but arrested cell division appears to be the primary mechanism of selectivity.

Atrazine inhibits photosynthesis in susceptible weeds and is in the triazine herbicide family. Triazines interfere with electron transport during photosynthesis and eventually lead to cell membrane destruction and cellular leakage. Susceptible weeds initially exhibit chlorosis on leaf margins. Actively growing bermudagrass is sensitive to atrazine applications and its addition to ethofumesate treatments provides postemergence and some residual control of bermudagrass. Atrazine alone may provide some bermudagrass suppression but does not provide long-term control.

Applications of ethofumesate with atrazine should be initiated during bermudagrass spring green up. Herbicide regimens that begin on actively growing bermudagrass in summer will likely be ineffective. St. Augustinegrass often responds to applications with stunted growth and discoloration. Repeat applications should be made after 30 days or once turf has recovered from any potential injury. See the current edition of the Georgia Pest Management Handbook for rates and further information about bermudagrass control.

Bermudagrass Control in Tall Fescue and Zoysiagrass

Fenoxaprop and fluazifop are used for postemergence grassy weed control in tall fescue and zoysiagrass. Sensitive weeds exhibit injured leaf tissue with reddish discoloration while plant nodes become necrotic and die. Theses herbicides have no activity on broadleaf weeds but provide excellent grassy weed control.

Fenoxaprop (Acclaim Extra) and fluazifop (Fusilade) may be used alone in tall fescue and zoysiagrass lawns. Fenoxaprop may also be used in residential and nonresidential Kentucky bluegrass (Poa pratensis L.), perennial ryegrass (Lolium perenne L.) and other cool-season turfgrasses. Fluazifop may be used in commercial and nonresidential turf. Generally, tall fescue has good tolerance to these herbicides. There is greater potential for injury on zoysiagrass than on tall fescue from fenoxaprop or fluazifop treatments, especially fine-textured varieties.

Triclopyr (Turflon Ester, Turflon Ester Ultra) at high rates (0.75 to 1 lb ai/acre) is injurious to bermudagrass. Tank mixtures with fluazifop or fenoxaprop have been shown to reduce tall fescue and zoysiagrass injury without compromising control. The addition of an adjuvant to tank mixtures of fluazifop with new triclopyr formulations (e.g., Turflon Ester Ultra) is unnecessary and may increase turf injury.

In Georgia, initial applications of fenoxaprop or fluazifop should be scheduled around June 1 and repeated every 20 to 30 days. Fluazifop alone should be applied with a non-ionic surfactant at 0.25% v/v of spray solution. Acclaim Extra (fenoxaprop) does not require the addition of an adjuvant. See the current edition of the Georgia Pest Management Handbook for rates and application comments for fluazifop and fenoxaprop treatments for bermudagrass control in tall fescue.

Nonselective Bermudagrass Control

Spot treatments of nonselective herbicides are the most effective method for controlling bermudagrass. Glyphosate is a nonselective herbicide that is widely used for spot treatments of perennial weeds in turfgrasses. Glyphosate is a foliar-absorbed herbicide that is systemically translocated with no preemergence activity for weed control.

Spot treatments of glyphosate should be made to bermudagrass patches and surrounding areas to control any runners that may be intermingled with desirable turfgrasses. Broadcast applications can effectively renovate or kill existing vegetation but high rates and multiple applications are required to control bermudagrass. Glyphosate should be applied to actively growing bermudagrass. Repeat treatments will be required for complete control. Cultural practices that disrupt plant growth, such as vertical mowing and aerification, should be delayed for seven days after treatment.

Glyphosate requires optimum translocation in order to control bermudagrass rhizomes and plants emerging from lateral stems. Perennial grasses generally have greater translocation of photosynthate from leaves to stems in fall than spring, which increases glyphosate movement to rhizomes. Fall glyphosate applications generally control bermudagrass more effectively than summer treatments. Numerous glyphosate products are available under a wide variety of trade names.

Other information in this publication

For pesticide recommendations see the UGA Pest Management Handbook.

What is this weed and how do we control it?

November 30, 2015July 1, 2014 by Willie Chance

Lespedeza McCullough — Common lespedeza in a centipedegrass lawn. Photo by Patrick McCullough.

This weed is common lespedeza. To learn about is biology and control, see this publication by Patrick McCullough, UGA Extension Weed Specialist. This information is taken from his publication.

Common lespedeza (Kummerowia striata (Thunb.) Schind syn. Lespedeza striata) is a freely-branched summer annual legume that is a problem weed in lawns and other turf areas. Common lespedeza, also known as Japanese clover or annual lespedeza, has three smooth, oblong leaflets with parallel veins that are nearly perpendicular to the midvein

Common lespedeza woody stems in late summer. Photo by P. McCullough.

As common lespedeza matures, the stems harden and become woody, which is attributed to persistence and competition with turfgrasses in late summer

Flowers are pink to purple and present in the leaf axils. Other lespedeza species may also be found as weeds in turf but common lespedeza is the primary species in Georgia.

Leaf of common lespedeza. Photo by Patrick McCullough

This publication gives information on

To see the entire publication click here.

Find other UGA publications here

Goats and Sheep Battle Invasive Plants

November 30, 2015June 16, 2014 by Willie Chance

The Athens-Clarke County Commission approved on June 3, 2014 a new law that will allow people inside the city limits to rent goats and sheep to help get rid of invasive plants on their property (info taken from the Center for Invasive Species blogspot). Read the following story to find out why.

The following article is by Merritt Melancon, news editor with the University of Georgia College of Agricultural and Environmental Sciences

Goats and sheep have a reputation for eating vegetation that most other grazing animals would not touch.

This trait makes them invaluable to people who need to raise livestock in tough climates, but it’s also made them popular for landowners who need to clear brush or invasive plants from overgrown parcels.

The nimble grazers can get into overgrown areas that even the most dedicated groundskeeper or gardener won’t chance. They’ve proven to be a low-impact, low-cost way to control invasive plants like privet, kudzu, honeysuckle and English ivy.

The practice of using sheep and goats to clear out unwanted brush is called targeted grazing, and many government agencies, municipalities and private landowners are using it to keep vacant lots, steep back yards, parks and right-of-ways clear of brush.

When is it time to bring in a herd?

Targeted grazing is a suitable option, whether a landowner is dealing with acres of stream bank, a detention pond or a small back yard, but it’s not meant to replace basic maintenance, said Brian Cash, owner of EWE-niversally Green sheep rental service in Dunwoody.

“We’re not a lawn mowing service,” Cash said. “We’ll do that, but we like to focus on overgrown yards and lots.”

Cash often works with new homeowners in and around downtown Atlanta who have purchased foreclosed homes with overgrown lawns and local government agencies needing to clear brush from public lands.

Sheep and goats are most useful when an area is so overgrown that no one else wants to clear it out. Even if its just a small yard, most homeowners, and many landscapers, don’t want to work in an area that’s choked with poison ivy, poison oak and briars, he said.

Sheep and goats are also useful in areas that are too steep or too wooded to use a tractor to clear out brush.

“If you can do it with a bush hog on a tractor, then that would be cheaper, but if you need a guy with a weed whacker out there, then I’m cheaper,” said herdswoman Jennif Chandler, of Shady Brook Farm in Colbert.

Chandler and her sheep have worked with the University of Georgia College of Agricultural and Environmental Sciences on the Athens campus to clear invasive plants including privet, kudzu and honeysuckle from along the bank of the Oconee River.

She also works with homeowners in the Athens area to clear Kudzu covered hills and backyards.

While goats and sheep are a surefire and efficient way to clear out a choked backyard or lot, there are a few things that homeowners should consider before buying a half-dozen goats or even hiring a service like Cash or Chandler’s.

They’ll eat everything

While herdsmen and women out on the West Coast are training goats and sheep to nibble around delicate plants like grape vines and other crops, targeted grazing isn’t a technique homeowners would want to try around their prize hydrangeas or a heirloom rose bush.

In fact, some ornamental plants are seriously toxic to sheep or goats. Examples include azaleas and Japanese yew.

“They’re not very discriminant,” said Sarah Workman, an Extension Agroforestry Specialist with the CAES. “If there’s something you don’t want them to eat, you need to protect it.”

While goats and sheep eat pretty much the same thing, sheep prefer broad-leaf weeds like ivy or kudzu, and goats seem to prefer woodier plants, Cash said.

Sheep usually can clear an area up to about a five-foot height, but goats can climb and take care of plants up to seven feet off the ground.

Because of their climbing ability, goats can take care of larger plants. However, that skill and natural curiosity, makes them more likely to escape and antagonize neighborhood dogs.

Cash usually sends a few goats along with his sheep herd to get the best of both worlds, but he’s careful to select his best-behaved goats.

Graze, wait and repeat

If a homeowner’s goal is to eradicate a specific invasive species, it may take repeated grazing to accomplish that goal, Workman said.

She and Chandler organized the first targeted grazing demonstration at UGA last year. The project, an effort to remove privet from a portion of the River Road area, is ongoing.”

These invasive plants are invasive because they are so persistent,” Workman said. “The idea is that the repeated introduction of the animals will deplete the root reserve of the (invasive) shrub.”

The shrubby stuff and woody vines are things that need repeated browsing,” Workman said. “And hopefully the more they’re eaten and knocked back, the less strength they have to regrow.”

Chandler’s sheep are scheduled to be back in action this summer to continue the eradication effort.

Managing the herd takes expertise

Herdsmen and women, like Cash and Chandler, have worked with their animals long enough to know how they’ll graze a specific area and how to meet homeowners’ goals for targeted grazing. Their customers get the benefit of that expertise when they rent their herds.

Another option is for a homeowner to purchase a few sheep or goats, but they need to be ready for the responsibility, said Will Getz, professor of animal science at Fort Valley State University’s Georgia Small Ruminant Research and Extension Center.

Zoning laws prohibit many suburban and urban homeowners from keeping any goats or sheep in their backyard. Additionally, suburban, urban and even rural landowners will face the challenge of keeping their herds contained and safe from neighborhood dogs or coyotes.

Moreover, there is the matter of food.

An acre of grass and brush can support about a half-dozen goats or sheep over the long-term, Getz said. If a landowner wants to load their land with more than six sheep or goats per acre, they’ll clear it out quickly.

“If you exceed that stocking intensity, then the animals are going to clear the area out more quickly,” Getz said. “But then you need to be prepared to sell them or otherwise get them off of your land when they’ve finished, either that or start buying feed.”

Homeowners interested it either renting or buying goats or sheep to clear their land should contact their local UGA or FVSU Cooperative Extension agent and the zoning or public development office in their county or city.

Can you identify and control this troublesome weed?

November 30, 2015June 6, 2014 by Willie Chance

Info taken from the publication Virginia Buttonweed Identification and Control in Turfgrass by Patrick McCullough and Jialin Yu, UGA Department of Crop and Soil Sciences

Virginia buttonweed (Diodia virginiana L.) is a troublesome broadleaf weed in turfgrass throughout the southeastern United States. Virginia buttonweed is a deep-rooted perennial with prostrate or spreading branches. It usually proliferates in moist to wet areas and can tolerate mowing heights as low as one-half inch. The species is a member of the Rubiaceae family and is found from New Jersey, west to Missouri and south into the Gulf Coast states.

Virginia buttonweed leaves are slightly thickened, opposite without petioles and slightly rough along the margins (Picture 1). Leaves are green on the upper surface, light green on the lower surface and often have a mottled yellow mosaic appearance caused by a virus that commonly infects foliage (Picture 2). Branched stems are occasionally hairy (Picture 3) and reproduction occurs via seeds, roots or stem fragments. Flowers are white with four star-shaped petals, which sometimes have pink streaks in the center and two sepals. Fruit are green, elliptically shaped, hairy and ridged.

For info on managing this weed:

See entire publication

Or see sections of the publication on:

GCIA Ensures Landscape Pros’ Access to Certified Turfgrass

November 30, 2015May 5, 2014 by Willie Chance

Billy Skaggs, GCIA Seed Certification Program Manager

Here in Georgia, the Georgia Crop Improvement Association (GCIA) ensures turfgrass professionals can purchase high quality seed and turfgrass sod which are free of noxious weeds, genetically pure, and guaranteed to germinate. GCIA is a non-profit organization, operating as an agent for the University of Georgia.

Certified seed and turfgrass are produced and increased under a limited generation concept that is supervised by GCIA. There are three classes of certified seed and turfgrass:

Foundation material which is produced from breeder stock
Registered material produced from foundation stock
Certified material produced from registered stock.

Each generation increase is field inspected by GCIA.

Turfgrass certification is the only quality control offered for protection of the sod buyer, as state and federal laws do not address vegetatively produced crops. Our turfgrass members produce “blue tag” certified sod which is field-inspected at least three times yearly by knowledgeable inspectors. Each inspector is trained to recognize off-type plants, other crops, noxious and objectionable weeds, which can create unsightly and costly problems in turf.

When only the best will do, many landscape architects specify Georgia certified “blue tag” turfgrass on their projects. When ordering sod or bidding jobs, be sure to specify Georgia Crop Improvement Association “blue tag” certified grass. The blue certificate assures you that the grass provided by your grower has met a rigorous set of inspection criteria designed to promote high quality, true to variety, and weed free turfgrass.

For more information, visit www.certifiedseed.org. And remember, Certified Sod Doesn’t Cost – It Pays!

Controlling Annual Bluegrass and Lespedeza in Turf

November 30, 2015April 22, 2014 by Willie Chance

Helpful publications from Patrick McCullough, UGA Extension Weed Specialist

Annual Bluegrass Control in Residential Turfgrass

Annual bluegrass (Poa annua L.) is a problematic winter annual weed in residential turf. Compared to most turfgrasses, annual bluegrass has a lighter green color, coarser leaf texture and produces unsightly seedheads.

Contrary to its name, both annual (live for one season) and perennial (live for many seasons) biotypes of annual bluegrass may be found in turf.

This publication describes methods of control for annual bluegrass in residential turfgrass lawns.

To see the entire publication visit this site.

Annual Bluegrass Control in Non-Residential Commercial Turfgrass

Lespedeza Identification and Control in Turfgrass

Common lespedeza is a freely-branched summer annual legume that is a problematic weed in lawns and other turf areas. Common lespedeza, also known as Japanese clover or annual lespedeza, has three smooth, oblong leaflets with parallel veins that are nearly perpendicular to the midvein. As common lespedeza matures, the stems harden and become woody, which is attributed to persistence and competition with turfgrasses in late summer. Flowers are pink to purple and present in the leaf axils. Other lespedeza species may also be found as weeds in turf but common lespedeza is the primary species in Georgia.

This publication describes ways to identify and control lespedeza in turfgrass, including:

To see the entire publication visit this site.

Here are other UGA turf weed control publications:

Apps help identify invasive pests

October 4, 2015December 16, 2013 by Willie Chance

Clint Thompson, news editor with the UGA College of Agricultural and Environmental Sciences

http://apps.bugwood.org/apps.html

Is there an unwanted invasive insect or plant on your farm or in your garden that you don’t recognize? The University of Georgia College of Agricultural and Environmental Sciences has an app for that.

Invasive species trackers at the UGA Center for Invasive Species and Ecosystem Health have developed a suite of apps to help farmers, forestry personnel and home gardeners identify strange unwanted invasive pests. They can now identify their problem invasive pests in the field, rather than breaking away to sit down at a computer and look it up.

Apps developed by the center’s technology director Chuck Bargeron and his co-workers provide direct links to different databases specializing in informing and educating the public about invasive species, those not native to an area that has been introduced and causing damage to agriculture and forestry. Such species include the kudzu bug that munches on soybeans and the spotted wing drosophila which affects blueberry crops.

“For the IOS platform, we’ve had more than 25,000 downloads of apps. The most successful one was the first one we did which was for Florida, which was focused primarily on pythons in south Florida. It’s probably been the most successful because it had the most press coverage when it first came out,” Bargeron said.

The app is one of 17 the center has developed. It provides different apps for different parts of the country because, for example, farmers in the Western United States aren’t concerned with the same species that growers in the Southeast are concerned with. Working a regional perspective allows users to focus on species in their geographic area.

Bargeron and members of the Center for Invasive Species and Ecosystem Health have had great success with database web-based resources of information, especially after the pictures image archive were added to the website in 2001. When Keith Douce and David Moorhead, — co-directors of the center formally known as Bugwood Network, — launched the website in 2001 they added pictures from 35mm slides. Approximately 3,500 pictures were available. As more and more people began using the website and recognizing its value, they started sharing their own pictures. The database of pictures increased greatly in the 12 years since the website was started. Now, more than 200,000 pictures from more than 2,000 photographers are in the systems database.

These resources have also changed the way forestry and agriculture classes are taught. An entomology professor at Texas A&M told Douce the resources caused him to completely restructure how he teaches his classes.

According to Douce, the center website generated 9.3 million users last year and 260 million hits.

For more information, visit the website at bugwood.org.

Conversion Tables, Formulas and Suggested Guidelines for Horticultural Use

September 24, 2015December 9, 2013 by Willie Chance

Bodie V. Pennisi, Gary L. Wade, Melvin P. Garber, Paul A. Thomas and James T. Midcap, Horticulture Department Originally prepared by S.C. Myers and A.J. Lewis, Extension Horticulturists

Formulas for calculating greenhouse volume

Uneven-span greenhouses
Quonset structures
Even-span greenhouses

Pesticide and fertilizer recommendations are often made on a pounds per acre and tons per acre basis. While these may be applicable to field production of many crops, orchardists, nurserymen and greenhouse operators often must convert these recommendations to smaller areas, such as row feet, square feet, or even per tree or per pot. Thus pints, cups, ounces, tablespoons and teaspoons are the common units of measure. The conversion is frequently complicated by metric units of measure. This publication is designed to aid growers in making these calculations and conversions, and also provides other data useful in the management, planning and operation of horticultural enterprises.

See the entire publication here

UGA mobile apps help professionals care for lawns

September 24, 2015October 28, 2013 by Willie Chance

Sharon Dowdy, News Editor with the UGA College of Agricultural and Environmental Sciences

Four mobile applications designed by University of Georgia specialists are putting lawncare information at your fingertips, literally.

The turfgrass apps created by UGA College of Agricultural and Environmental Sciences faculty make turf management in Georgia readily available. Turfgrass Management, Turf Management Calculator, Turfgrass Weeds and Turf Management Quiz can all be downloaded from the UGA Turfgrass Team website at www.GeorgiaTurf.com or straight to a mobile device through iTunes.

A lite version

The most popular UGA turfgrass app is Turf Management Lite. This free app was created with students, homeowners and professionals in mind. It includes photos of turfgrass varieties, pests, weeds and diseases.

Mobile applications, or apps as they are commonly called, can be downloaded onto smart phones like Droids and iPhones as well as portable tablets like iPads.

“Back in 2009, mobile apps were fairly new to smart phones. We saw a great opportunity to put the information where it can be easily accessed by mobile phone, iPods and tablets, instead of publishing a telephone-book-sized publication,” said Patrick McCullough, a UGA turfgrass specialist based on the Griffin campus. The turfgrass apps are his brainchild.

“Rather than have to go to the office and get an Extension publication or go online to view a publication, turfgrass professionals can now access the information they need in the field,” he said.

In-depth subscription version

There are three versions of the first app: Turf Management Lite, Turf Management Subscription and Turfgrass Management – Spanish. The lite and Spanish versions are free, but the subscription version costs $20 per year.

The subscription version includes everything from the lite version, plus information on pest control applications and a pesticide database. “You can search for trade names as well, and it includes PowerPoint presentations from UGA turfgrass faculty,” McCullough said.

The Spanish version is very popular in the turfgrass industry. “We have folks in the industry that speak Spanish as their first language. This app is a nice opportunity for those who are fluent in Spanish or primarily communicate in Spanish at work to have research-based turfgrass advice,” he said.

The Spanish version has been downloaded in more than 40 countries across the globe.

Making calculations easy

In 2011, the Turfgrass Management Calculator app was released. “It’s a comprehensive program that covers all types of applications, pesticide rates, fertilizer requirements, topdressing sand requirements, and calibration of sprayers and spreaders. Users enter known values of equations – like how much area is needed for a pesticide treatment at a certain rate. The app then does the calculation for you,” McCullough said.

College students majoring in turfgrass management use the app to double-check their math when learning these calculations, he said. “Some of these are very complex formulas. You can enter information for two products with different application rates and see which is more cost effective.”

The calculator app costs $5 and includes more than 16,000 pre-programmed calculations. It can also convert units from standard to metric. “It’s really a great tool for turfgrass managers and professionals, but students can learn a lot from it, too,” McCullough said.

Flash cards and quizzes

The Turfgrass Weeds app was released in 2011. It is designed to help users learn turfgrasses and weeds through a series of flash cards. “The cards reshuffle so users can continue to study and learn turfgrass species and weeds,” he said.

Just a few months ago, the UGA Turfgrass Team released its latest turfgrass app – Turfgrass Management Quiz.

“This app is a trivia style education game. You get test questions or photos with four choices to answer. You tap the correct answer, and when you’re done, you get a quiz score,” McCullough said.

The quiz app has two modes – quiz mode and study mode. Quiz mode scores your answers and study mode helps you get the correct answer.

“This app is perfect for students, but it can also be used by any turfgrass professional who wants to brush up on their knowledge. It’s a fun application that challenges you to get the best score, improve on your score and test your knowledge,” he said.

The new turfgrass apps are perfect for those who like to learn on their phones or mobile devices. UGA publications are also available online for computer users and in print form for those who still like the feel of a book in their hands.

“(Mobile apps) are a new technology – a new method to get information in the hands of the end user. We are trying to make it easier for people to get UGA turfgrass recommendations so it just makes sense for us to create these programs,” McCullough said.

To download the UGA turfgrass mobile apps or get more information on the turfgrass research at UGA, see the website www.GeorgiaTurf.com.

Prepare Now for Annual Bluegrass (Poa annua) Emergence this Fall

November 30, 2015August 29, 2013 by Willie Chance

Patrick McCullough, Extension Weed Specialist, University of Georgia

Annual weeds establish from seed and complete their lifecycle in one year. Summer or warm-season annual weeds (like crabgrass) establish in spring, grow actively in summer, and die out in fall. Winter or cool-season annual weeds (like annual bluegrass) establish in fall, grow from fall to spring, and complete their lifecycle in warm temperatures in late spring.

Failure to control annual weeds in late summer may predispose turfgrasses to winter weed infestations. In many lawns, it is fairly common to see turf with significant summer crabgrass populations have problems with annual bluegrass in fall. Open areas left in turf where crabgrass was once actively growing may permit annual bluegrass invasion during periods of peak seed germination. Controlling crabgrass now or in late summer could significantly improve turf cover, growth, and competition with annual bluegrass. See Table 1 for postemergence herbicide selection for crabgrass control in turf.

Late Summer Crabgrass Control Can Improve Annual Bluegrass Control This Fall

Quinclorac is a popular postemergence herbicide selection for crabgrass control in bermudagrass, zoysiagrass, and many cool-season grasses.

Single applications of quinclorac have excellent activity on mature, multi-tiller crabgrass plants at the seedhead stage in late summer. Bermudagrass, creeping bentgrass, perennial ryegrass, tall fescue, and zoysiagrass can be safely seeded seven days after a quinclorac application. Quinclorac requires the addition of an adjuvant, such as crop oil or methylated seed oil, for best results in established turf.

Mesotrione (Tenacity) can be used for postemergence crabgrass control in centipedegrass, perennial ryegrass, St. Augustinegrass, and tall fescue.

Mesotrione should be applied with a nonionic surfactant and will require two applications at a three week interval for late summer crabgrass control. These turfgrasses can also be safely established following mesotrione applications for crabgrass control. Currently, Tenacity can be used in nonresidential turf but will have residential lawns added to the label in the near future.

Fenoxaprop (Acclaim Extra) is a postemergence grassy weed herbicide for use in tall fescue, perennial ryegrass, and zoysiagrass.

Fenoxaprop has excellent activity on multi-tiller crabgrass with one application but efficacy is often reduced when crabgrass has seedheads present. Tall fescue and perennial ryegrass may be safely reseeded immediately after fenoxaprop applications. Late summer seeding of zoysiagrass is not recommended but newly plugged or sodded zoysiagrass may be treated with fenoxaprop.

Late Summer Cultural Practices to Reduce Annual Bluegrass Competition

Promoting turfgrass recovery from summer stress is critical to reduce annual bluegrass competition in fall.

Review cultural practices and make modifications if needed for lawns with crabgrass problems during summer months.

Mowing height significantly influences turfgrass competition with crabgrass, annual bluegrass, and other problem weeds.

Height of cut for most lawns should be no less than two inches. Raising the mowing height of tall fescue, for example, to three inches may significantly reduce annual bluegrass establishment in fall and reduce the need for postemergence herbicides in spring. Check mowing height for your turf-type.

Mowing frequency also influences turfgrass growth and susceptibility to annual bluegrass infestations.

Turf managers should mow lawns at least once per week during periods of vigorous growth to prevent scalping. Scalping thins out turf and may enable annual bluegrass establishment in open areas. While returning clippings is recommended to recycle nutrients to the soil, removal of clippings may be useful when annual bluegrass is present and producing seed heads. Removing clippings at this time will reduce the spread of viable seed through the lawn.

Encouraging turf recovery from summer stress may include modifications to fertilization programs.

Turf managers should consider reducing nitrogen fertilization during peak annual bluegrass germination and during periods of vigorous growth (cool weather). High nitrogen at these times encourages annual bluegrass spread and survival into winter and spring. Fertilizing dormant turfgrasses when annual bluegrass is actively growing will make these weed infestations worse.

Fall aerification of cool-season grasses may also influence annual bluegrass infestations.

Open areas of bare soil in turf following an aerification may encourage annual bluegrass infestations during periods of peak seed germination. Time aerifications in early fall to allow turf to recover before annual bluegrass germinates.

+ More