Preemergence Herbicides for Annual Bluegrass

Patrick McCullough, Extension Weed Specialist, University of Georgia

Preemergence herbicides may prevent annual bluegrass infestation via seed and limit current infestations from further spreading.  However, preemergence herbicides will not eradicate established plants and will not effectively control perennial biotypes of annual bluegrass from spreading vegetatively.

Poa annua, Joseph M. DiTomaso, University of California - Davis
Annual Bluegrass, Joseph M. DiTomaso, University of California – Davis, Bugwood.org

Application timing of preemergence herbicides for annual bluegrass control is very important. Herbicides must be applied in late summer/early fall before annual bluegrass germination.  This info on timing herbicide application is taken from an article online by Tim Murphy, UGA Weed Scientist. “Annual bluegrass germinates in the late summer and early fall when daytime temperatures consistently drop into the mid-70os and nighttime temperatures are in the mid-50os for several days. In the Piedmont of Georgia for winter annual weed control, apply the preemergence herbicide sometime during the first two to three weeks of September (by September 20). In north Georgia, the last week of August up to about September 15 would be the preferred time. In South Georgia, the application should be made during the mid-September to mid-October time frame.”

A second herbicide application can be applied in spring to control germinating plants.  Fall applied preemergence herbicides cannot be used if reseeding or re-sodding is needed to repair areas of damaged turf within several months after herbicide applications.

Several preemergence herbicides effectively control annual bluegrass in fall and winter which are similar to products used for summer annual weed control (Table 2).  These herbicides include dithiopyr (Dimension), oxadiazon (Ronstar, Starfighter), pendimethalin (Pendulum, others), and prodiamine (Barricade, others).

Combination herbicide products are also available which may improve efficacy of applications.  These products include oxadiazon plus bensulide (Anderson’s Crab and Goose) and benefin plus oryzalin (Team 2G or Team Pro).  Many preemergence herbicides are available under a wide variety of trade names and formulations. Carefully read and follow label instructions before applying products.

Most preemergence herbicides will provide similar initial efficacy if applied before annual bluegrass germination and if sufficient rain or irrigation is received.  Preemergence herbicides require incorporation from irrigation or rainfall so that weeds may absorb the applied material.  In order to effectively control annual bluegrass, preemergence herbicides must be concentrated in the upper 1/3 inch of the soil profile.  Avoid herbicide retention on leaves and incorporate the herbicide into the soil by irrigating turf immediately after application.

Table 1.  Efficacy of postemergence herbicides for crabgrass control in turfgrasses.  See labels for turf tolerance and areas for use.

Postemergence Herbicides for Crabgrass Control

Common NameTrade Name (Examples)

Control

ClethodimEnvoy

E

FenoxapropAcclaim Extra

E

MesotrioneTenacity

F-G

QuincloracDrive, Drive XLR8

E

SethoxydimSegment, others

E

E = Excellent (90 to 100%), G = Good (80 to 89%), F = Fair (70 to 79%), P = Poor (<70%).

 

Table 2.  Efficacy of preemergence herbicides for annual bluegrass control in commercial turfgrasses.

Preemergence Herbicides for Annual Bluegrass Control

Common NameTrade Name (Examples)

Control

AtrazineAatrex, others

E

BenefinBalan

E

BensulideBetasan, others

F

DithiopyrDimension

G

EthofumesatePrograss

G-E

MesotrioneTenacity

F

OryzalinHarrier, Surflan

G

OxadiazonRonstar, Starfighter

G

PendimethalinPendulum, others

G

ProdiamineBarricade, Cavalcade, others

E

PronamideKerb

E

SimazinePrincep, WynStar, others

E

E = Excellent (90 to 100%), G = Good (80 to 89%), F = Fair (70 to 79%), P = Poor (<70%).

 

Helpful publications from UGA Extension on controlling annual bluegrass

 

Annual Bluegrass Control in Residential Turfgrass

Patrick McCullough, Extension Weed Specialist

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

To see the entire publication go here.

Topics:

 

Annual Bluegrass Control in Non-Residential Commercial Turfgrass

Patrick McCullough, UGA Department of Crop and Soil Science

Turfgrass Disease Update – Gray Leaf Spot and Rust

Rust on zoysia

Alfredo Martinez, Extension Plant Pathologist

Time to scout for gray leaf spot

Gray leaf spot is a fungus disease that affects St. Augustinegrass, perennial ryegrass and tall fescue in Georgia. Hot humid summer weather and high nitrogen levels can make turf susceptible to this disease. The fungus causing the disease is Pyricularia grisea.

Read moreTurfgrass Disease Update – Gray Leaf Spot and Rust

Lespedeza Identification and Control in Turfgrass

Lespedeza McCullough

Edited from a publication by Patrick McCullough, UGA Extension Weed Specialist

See the entire publication here

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

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 gives information on

To see the entire publication click here.

Find other UGA publications here

Photo credit – Common lespedeza in a centipedegrass lawn. Photo by P. McCullough.

Cool Season Turfgrass Disease Update

Alfredo Martinez, UGA Extension Plant Pathologist

It is time to scout for Brown patch (caused by Rhizoctonia solani) and Pythium blight (caused by Pythium spp). These diseases are often the most serious diseases on cool season grasses, especially on tall fescue and ryegrass                      

Brown patch can cause a foliar blight, which results in necrotic leaves and circular brown patches up to 4-5 ft. in diameter. High soil and leaf canopy humidity, and high temperatures increase disease severity. Higher than recommended rates of nitrogen in the spring promotes disease.

Management options include:

  • Avoid nitrogen application when the disease is active
  • Avoid infrequent irrigation and allow the foliage to dry
  • Mow when grass is dry
  • Ensure proper soil pH
  • Thatch reduction and
  • Improve soil drainage.

Pythium MartinezPythium blight has the potential to quickly cause significant damage to turfgrass. The disease starts as small spots, which initially appear dark and water-soaked. Affected turfgrass dies rapidly, collapses, and appears oily and matted. White, cottony mycelia may be evident early in the morning. The disease is driven by hot-wet weather, which correlates with an increased stress on the turf. Similar environmental and cultural factors that encourage brown patch also promote Pythium. Therefore, cultural practices for control of brown patch will also help to minimize Pythium blight development. A correct diagnosis is important because Pythium control requires specific fungicides.

Several fungicides are available for each of the diseases described above. Consult the Georgia Pest Management Handbook or the Turfgrass Pest Control Recommendations for Professionals for proper fungicide selection and usage. Read the label and follow proper guidelines.

For more information on these diseases visit:

For Brown Patch

For Pythium blight