Pest Control Alerts

What are the best post-emergence herbicides for annual bluegrass control in turf?

by
Annual bluegrass - Robert Vidéki, Doronicum Kft., Bugwood.org
Annual bluegrass – Robert Vidéki, Doronicum Kft., Bugwood.org

Postemergence Annual Bluegrass Control in Turf

Patrick McCullough, Extension Weed Specialist, University of Georgia

Edited from a more complete article which can be found here.

Contrary to its name, both annual (live for one season) and perennial (live for many seasons) populations of annual bluegrass may be found in turf.  Annual bluegrass may out-compete other turf species during late fall and early spring.  Annual bluegrass often dies from summer stresses but may survive if irrigated – especially the perennial biotypes

Postemergence Control (See Table 3)

Annual bluegrass may be selectively controlled with postemergence herbicides (Table 3).

Landscapers managing warm-season grasses have more options for selective postemergence annual bluegrass control than cool-season grasses.

Flazasulfuron (Katana), foramsulfuron (Revolver, Tribute Total), rimsulfuron (TranXit), and trifloxysufluron (Monument) are labeled for bermudagrass and zoyiagrass non-residential commercial lawns and other sites.  Flazasulfuron and rimsulfuron are also labeled for use in centipedegrass. Efficacy of these herbicides generally increases under warm temperatures in spring compared to winter and non-ionic surfactants may enhance efficacy.

Pronamide (Kerb) is a restricted use herbicide for annual bluegrass control in non-residential bermudagrass, centipedegrass, St. Augustinegrass, seashore paspalum, and zoysiagrass.  Pronamide is root-absorbed and must be watered in following applications.  Pronamide efficacy is generally slower than most sulfonylureas and activity for annual bluegrass control may take approximately four to six weeks.

Atrazine (Aatrex, Bonus S, others) and simazine (Princep, WynStar, others) may also be applied to bermudagrass, centipedegrass, St. Augustinegrass, and zoysiagrass for selective postemergence annual bluegrass control.  These herbicides often provide erratic control of annual bluegrass but may control other grassy and broadleaf weeds.  Actively-growing bermudagrass is sensitive to atrazine and applications are recommended only during the late fall and winter months.

Dormant bermudagrass may be treated with nonselective herbicides, such as glyphosate (Roundup, Touchdown, others), glufosinate (Finale), and diquat (Reward).  These herbicides will injure or kill existing vegetation, including annual bluegrass and managers should only spray at peak dormancy when no green turfgrass foliage is observable.  Nonselective herbicides should only be applied to completely dormant bermudagrass and applications during early spring may delay greenup with significant turf injury.

Flumioxazin (Sureguard) is a new herbicide for pre- and postemergence annual bluegrass control but applications are limited to dormant bermudagrass only.  Flumioxazin use after greenup or on other species are not recommended due to excessive injury potential.

Selective annual bluegrass control options in cool-season lawns are limited.

Ethofumesate (Prograss) controls established annual bluegrass in perennial ryegrass, tall fescue and dormant bermudagrass (see the current edition of the Georgia Pest Management Handbook). Two or three ethofumesate applications may be applied in late fall at three- to four-week intervals. Annual bluegrass control may be seen that fall, but control is usually observed the following spring. Annual bluegrass control with ethofumesate may vary greatly over years depending on environmental conditions.

Amicarbazone (Xonerate) is a new Photosystem II inhibitor, similar to triazine herbicides, but may be used in tall fescue lawns and other cool-season grasses.  Applications of amicarbazone in Georgia are limited to springtime only to minimize injury to cool-season grasses.  Warm-season turf is very tolerant to amicarbazone and may be treated at any seasonal timing.

Bispyribac-sodium (Velocity) has shown potential for selective annual bluegrass control in tall fescue and perennial ryegrass lawns.  However, this herbicide is currently registered for creeping bentgrass and perennial ryegrass on golf courses and sod farms only.  Spot treatments of nonselective herbicides are generally the most effective treatment regimen for annual bluegrass control in cool-season grasses.

Table 3.  Efficacy of postemergence herbicides for annual bluegrass control in turfgrass.

Common Name Trade Name (Examples) Efficacy
amicarbazone Xonerate F-G
atrazine Aatrex, others E
bispyribac-sodium Velocity F-G
flazasulfuron Katana G-E
flumioxazin Sureguard F-G
foramsulfuron Revolver E
glufosinate Finale E
glyphosate Roundup, others E
imazaquin Image P-F
metribuzin Sencor G
pronamide Kerb E
rimsulfuron Tranxit E
simazine Princep, others G-E
thiencarbazone + foramsulfuron + halosulfuron Tribute Total G-E
trifloxysulfuron Monument E

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

For more information

Annual Bluegrass Control in Residential Turfgrass

Annual Bluegrass Control in Non-Residential Commercial Turfgrass

Georgia Mosquito Control Association plans for threat of chikungunya virus next spring

by
mosquito April Sorrow UGA
Georgia mosquito control professionals gathered in Athens this month to discuss the 2015 mosquito season. Image credit: April Sorrow, UGA.

Merritt Melancon is a news editor with the University of Georgia College of Agricultural and Environmental Sciences.

As Georgia’s mosquito season draws to a close, mosquito control professionals are looking back, evaluating the season and planning for the challenges they will face next spring.

At the top of the list of concerns, voiced at the Georgia Mosquito Control Association (GMCA) meeting this month at the University of Georgia, was chikungunya, a viral disease spread by certain mosquitoes that causes severe joint pain and flu-like symptoms. Drawing on the lessons they’ve learned from battling West Nile Virus outbreaks for the last decade, mosquito control professionals are working with UGA entomologists and Georgia’s public health officials to stay one step ahead of the painful disease come next spring.

“The GMCA meeting is a great time for mosquito control professionals in Georgia to gather and share information about emerging threats and the best efforts to protect the public from these pests and diseases,” said Elmer Gray, UGA Extension mosquito specialist and board member of the Georgia Mosquito Control Association.

The disease is rarely fatal, but it is painful and, in some cases, has caused long-term joint pain, said Rosemarie Kelly, an entomologist with Georgia Department of Public Health.

It’s described as one of those things that, intellectually, you know you’re not going to die of, but you kind of wish you would,” she said.

The virus is spread person-to-person by container-breeding mosquitoes and was first diagnosed in the Western Hemisphere in December 2013. Since then it has spread prolifically in South America and the Caribbean.

In Georgia, there have been 21 travel-related cases of chikungunya reported to the state Department of Public Health since this summer. All of these patients had traveled on mission trips or vacations to Latin America and contracted it there.

It has yet to be spread from person-to-person in Georgia because the mosquito that spreads the disease most efficiently – the yellow fever mosquito, or Aedes aegypti – is fairly rare here. In Florida, where the yellow fever mosquito population is larger, public officials started to see locally transmitted cases of the disease this summer – 11 to date.

Even though the yellow fever mosquito is rare in Georgia, epidemiologists and entomologists are worried that the Asian tiger mosquito – an invasive mosquito that has spread to every county in the state – could also spread the virus.

Over the course of the three-day conference, mosquito control officials learned the importance of developing close relationships with their local health departments as well as how trapping and identifying mosquitos can help them determine where they need to focus mosquito eradication efforts.

In an ideal situation, mosquito control would be notified when someone is diagnosed with chikungunya, and they could work to knock down the mosquito population near that house to minimize the chance of it spreading, Kelly told the mosquito control and private pest control operators at the conference.

“The sooner you know about new cases, the sooner you get control of those mosquito populations, and the sooner you can stop the spread of the illness,” Henry Lewandowski, director of Savannah’s mosquito control program, told the crowd.

Georgians who are diagnosed with chikungunya or suspect they have it after returning from their travels should avoid mosquito exposure for 10 days. Ten days after the onset of symptoms, the virus will have left the body and can no longer be transmitted via mosquito.

As with West Nile Virus and other mosquito-borne diseases, the best defense is a good offense, Gray said. Gray recommends that Georgians routinely clear their yards of containers that can hold water, providing a breeding habitat for mosquitoes. He also recommends using a mosquito repellent containing DEET when spending time outdoors.

For more information about chikungunya, visit cdc.gov/chikungunya or search for “chikungunya” at dph.georgia.gov.

Understanding Formulations Used As Liquid Sprays

by

From the publication Insecticide Basics for the Pest Management Professional

By Daniel R. Suiter, UGA Department of Entomology & Michael E. Scharf, UFL Department of Entomology and Nematology

 

Formulations commonly applied as liquid sprays are:

  • emulsifiable concentrates (abbreviated as EC)
  • wettable powders (WP)
  • suspension concentrates (SC)
  • microcaps (ME [microencapsulates] and CS [capsule suspensions])

 

These formulations must be diluted with water before they can be applied.

 

Emulsifiables are formulations that allow a water-insoluble insecticide to be suspended in water. Water and oil do not mix unless an emulsifying agent is added. When an emulsifier is added to a mixture of oil and water, microscopic droplets of oil are formed that disperse throughout the water. The resultant milky-white mixture is referred to as an emulsion.

 

Contact insecticides must be hydrophobic (insoluble in water) in order to penetrate the insect cuticle and/or interact with target sites. Although insoluble in water, most insecticides are soluble in oil or another solvent. To form an insecticide-active emulsion, the insecticide is dissolved in the solvent. When the emulsifier is then added, the resulting milky-white emulsion contains microscopic droplets of insecticide-impregnated solvent that become dispersed evenly throughout the water, as described in the previous paragraph. This resultant formulation can then be sprayed.

 

The droplets in emulsifiable formulations do not settle like suspensions and, therefore, require minimal agitation in comparison to formulations that are suspensions (wettable powders, microencapsulates, suspension concentrates).

 

Because emulsifiables readily absorb into skin, appropriate precautions should be used to minimize contact.

WP settling
Several liquid spray formulations (wettable powders, suspension concentrates, and microcapsules) form true suspensions, and will settle out of water when given sufficient time. In these photographs, a suspension concentrate was diluted in water at 4:00 p.m. (top photograph). The following morning, the solid, particulate matter had settled to the bottom of the glass beaker (bottom photograph), and required agitation to re-suspend the product.

Wettable powder formulations are created by impregnating or coating a microscopic particle of an inert carrier (e.g., adsorptive clay, talc, etc.) with insecticide and various inert ingredients to enhance the wetting, spreading, and dispersing characteristics of the powder.

 

The inert ingredients (wetting agents) allow the dry powder to evenly disperse in and mix with water without clumping or caking.

 

Because wettable powders are true suspensions, constant agitation is required to keep the powder suspended in water.

Wettable powders do not readily absorb into skin, but care should be taken when using this formulation to avoid accidental inhalation.

Suspension concentrates can be considered wettable powders that have been packaged in liquid formulation. They consist of very small crystals of technical grade insecticide mixed with an extremely fine, inert dust, a small amount of water, and various other inert ingredients. The inert ingredients enhance the dispersion and mixing characteristics of the formulation when diluted with water.

Because suspension concentrates settle out of suspension, they require constant agitation (Figure 1).

Microencapsulated products are formed by encapsulating an insecticide in a microscopic, round, plastic capsule. The capsules are mixed with inert ingredients (dispersants, wetting agents, etc.) to keep them from clumping and to help the mixture flow more readily. The inert ingredients also facilitate storage and dispersion when diluted in water.

The capsule’s wall thickness determines the release rate of the insecticide to the outside environment. The insecticide seeps through the capsule’s wall and coats the outside of the capsule. As the insecticide disappears (degradation, evaporation, etc.) additional insecticide inside the capsule continues to coat the capsule surface. This process maintains a capsule that is constantly coated with a thin film of insecticide.

The manufacturer can change the characteristics of the capsule wall to slow (or accelerate) the release rate of the chemical from inside the capsule, thus altering the residual life of the treatment. Changing the characteristics of the capsule can alter the product’s odor (slower release rates result in less smell); protect the chemical from environmental degradation; influence the rate of kill by the insecticide (faster release rates mean a faster rate of kill); and reduce exposure to non-target organisms.

Because microcaps settle out of suspension, constant agitation is required.

 

Bacterium May Make Mosquitoes Less Susceptible to Dengue and Malaria

by

anophelesgambiaemosquito-wp2 Ent TodayTaken from 

Just like those of humans, insect guts are full of microbes, and the microbiota can influence the insect’s ability to transmit diseases. A study published in PLOS Pathogens reports that a bacterium isolated from the gut of an Aedes mosquito can reduce infection of mosquitoes by malaria parasites and dengue virus. The bacterium can also directly inhibit these pathogens in the test tube, and can shorten the life span of mosquitoes that transmit both diseases.

George Dimopoulos and colleagues from Johns Hopkins University had previously isolated Csp_P, a member of the family of chromobacteria, from the gut of Aedes aegypti mosquitoes, which transmit dengue fever. In their present study, they examined its actions on both mosquitoes and pathogens. The results suggest that Csp_P might help to fight malaria and dengue fever at different levels.

Read more at 

Preparing Nursery Plants for Winter in the Southeastern United States

by

A new publication from UGA and other southeastern universities equips nursery workers (and others) to protect container and dug plants from freezing temperatures. The publication explains winter acclimatization and how cultural practices (pruning, watering, fertilization, etc.) can impact cold hardiness. The publication also discusses the types of winter injury and methods to protect plants from winter temperatures.

Find the publication online here.

The following is a brief list of some of the Strategies and Techniques to Protect Plants

  1. Push pots together in large blocks.
    1. Wrap outside edge of plants with microfoam, spunbond nonwoven polyester material, or pine straw bales to protect from wind. No protection on inside containers.
    2. Mulch in and around plants on the inside of the block using:
      i. Newspaperwinter protection
      ii. Pine straw, hay, or some other grain
      iii. Leaves or other composted material
    3. Cover blocks of plants with microfoam or spunbond nonwoven polyester fabric.
      i. Cover fabric with white polyethylene.
      ii. Use mulches under the fabric.
  2. Overwinter plants inside a quonset-style greenhouse or similar structure.
    1. Place single-layer white poly cover on house.
      i. Push plants close together with no further protection.
      ii. Cover plants inside structure with microfoam or spunbond nonwoven polyester.
      iii. Heal plants in with mulch.
    2. Place double-layer white poly cover on house with inflator fan to create an insulating dead-air space between plastic covers.
      i. Also cover plants with microfoam or spunbond nonwoven polyester.
      ii. Provide an independent heat source inside the house:

      1. Portable forced-air heater that runs on fuel or electricity
      2. Permanent propane, electric, or wood-fired heater

Note: Organization of ideas based on Dunwell and McNeill, 2009.

Insect pests invade Georgia homes in the fall

by

There are several insect pests that try to invade homes in the fall looking for over-wintering sites. Two are relatively new introductions to Georgia.

Kudzu bug Suiter AmesKudzu bugs (Megacopta cribraria): Wider posterior than anterior, about 3/16 to 1/4 inch. Red eyes, green to brown body with stipples present on wing covers. Distinct odor.

Habits: Flies to light-colored surfaces (buildings and automobiles), from nearby kudzu patches, in October/November as it looks for overwintering sites. Active again in Spring (February to April) as it awakes from Winter slumber. Native to Asia, was discovered in Georgia (and the Western Hemisphere) for the first time in October 2009. Feeds on kudzu as well as other legumes, including soybeans.

Interventions: Before kudzu bugs begin to move (October), take action to (1) seal all cracks 1/8 wide or wider, and (2) spot spray around all potential entry points with an appropriately labeled residual spray. Reapply insecticide treatments, per label specifications, through the end of November. Interventions should be implemented early enough (mid-September) so that preventative measures are in place before the onset of kudzu bug movement. In Summer, remove kudzu if possible. It is especially important to make sure all windows are screened, that doors remain closed, and doorsweeps are installed on all exterior doors. As temperatures decline into the Winter months kudzu bugs become less of a nuisance.

For more information see University of Georgia Extension circular #991, Megacopta cribraria as a Nuisance Pest.

Might Be Confused With: lady beetles, brown-marmorated stink bugs.

 

BMSB Suiter AmesBrown-Marmorated Stink bugs (Pentatomidae: Halyomorpha halys): Brown marbled- or mottled-colored stinkbug, 5/8 inch, adults with distinctive white-banded antennae.

Habits: First discovered in northwest Georgia in 2010, this invasive Asian species was first reported in the U.S. in Pennsylvania in 1996. An important agricultural pest of fruit crops as well as row crops and vegetables. Like the kudzu bug, boxelder bug, and multicolored Asian lady beetle, this bug is attracted to homes in the Fall in search of overwintering sites, sometimes in large numbers.

Interventions: Follow suggestions under section titled Proactive Pest Management, especially the installation of doorsweeps and screens. Before brown-marmorated stink bugs begin to seek refuge indoors (Fall), take action to (1) seal all cracks 1/8 wide or wider, and (2) spot spray around all potential entry points with an appropriately labeled residual spray. Reapply insecticide treatments, per label specifications, through the end of November. Interventions should be implemented early enough (mid-September) so that preventative measures are in place before the onset of stink bug migration indoors. It is especially important to make sure all windows are screened, that doors remain closed, and doorsweeps are installed on all exterior doors. If bugs get inside the best solution is to vacuum them. Insecticide treatments indoors are not recommended. If bugs die inside walls or in attics their carcasses can accumulate and attract other insects that eat them, especially carpet beetles.

Might Be Confused With: kudzu bugs, lady beetles.

What are these large spiders found in the landscape?

by

The picture is of a Yellow Garden Spider which are often seen in the landscape in late summer and fall. Read on to learn more about this and another fall spider.

Late Summer & Autumn Spiders

Nancy C. Hinkle, UGA Department of Entomology 

Between now and Halloween we will be seeing more spiders around our yards.  The first hard frost will kill them off. Now they are mating and producing egg sacs so their eggs can overwinter and re-establish the population next spring.  There are two orb-weaver spiders with large webs that are most commonly seen.

Barn spiders (Araneus cavaticus) can be found on porches, where flying insects attracted to porch lights get trapped in their webs.  These spiders are nocturnal, constructing a new web every evening and taking it down before dawn.  This rusty brown spider has legs extending about 2 inches, making it look large and noticeable.  These spiders hide during the day, but at night are found in the middle of the web, waiting for insects to be trapped.

The yellow garden spider (Argiope aurantia) is one of the longest spiders we have here in Georgia.  It is frequently found in gardens and around shrubbery where it constructs large webs to entrap flying insects.  The abdomen has distinctive yellow and black markings while the front part of the body, the cephalothorax, is covered in white.

The female yellow garden spider typically remains in one spot throughout her life, repairing and reconstructing her web as it is damaged and ages.  Her web may have a distinctive zigzag of silk through the middle, explaining its other common name, “writing spider.”  Unlike the nocturnal barn spider, the yellow garden spider can be found in its web anytime.  Sometimes a smaller spider will be found in the web with her; this is the male garden spider.

These spiders have been present all summer, eating pest insects and growing.  By late summer they are large enough that people start noticing them.  Remember,Georgia has over 800 species of spiders, all of which are harmless if you leave them alone.  All spiders are more afraid of you than you are of them.

For more information:

Call your local Extension Agent at (800) ASK-UGA1 or locate your local Extension Office.

Stinging and Biting Pests of People

Golden Garden Spiders

Pest Management Handbook Follow all label recommendations when using any pesticide

Carpet beetles can be more common in the fall

by

Carpet beetle from pubThis pest is a carpet beetle – adult and larvae. See this information from Management of Pest Insects in and Around the Home

Carpet beetles (Dermestidae: Anthrenus spp.): Adults 1/16 to 1/8 inch, ovalshaped, and calico colored. Larvae 1/8 inch, hairy, oval-shaped, slow-moving, and cryptic.

Habits: Most homes are populated by a small number of carpet beetles, but because they are somewhat cryptic (slow moving, small, and inconspicuous) they are rarely seen. Larvae, but not adults, feed on products in the home that are of animal origin (feathers, wool, fur, hair, silk, skins, dry animal food, etc.) but will also feed on dead insects (found on window sills, in wall voids, and in light fixtures). Carpet beetles do not consume modern shirts and carpets, as they are made from cotton or synthetic fibers. Adults feed on pollen outdoors.

Interventions: Find infested article(s) and remove. Vacuum insects and discard bag, and especially watch for re-infestation. Wash, steam-clean or dry-clean all items of animal origin, especially wool. Have infested textiles professionally cleaned. If desired, apply a spot treatment with an appropriately labeled residual spray to the floor around the infested item(s).

Might Be Confused With: warehouse beetle (Dermestidae: Trogoderma variabile), bed bugs.

For information on these and other insects see Management of Pest Insects in and Around the Home

Researchers Find Bacteria in Raw Honey that Could Replace Antibiotics

by

September 9, 2014 by

Researchers at Lund University in Sweden have identified a unique group of 13 lactic acid bacteria found in fresh honey that produce a myriad of active antimicrobial compounds. These lactic acid bacteria were tested on severe human wound pathogens — such as methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa and vancomycin-resistant Enterococcus (VRE) — and the lactic acid bacteria counteracted all of them.

Read entire article from 

What are the best methods to prevent annual bluegrass in turf?

by

Pre-emergence Annual Bluegrass Control in Turf

Patrick McCullough, Extension Weed Specialist, University of Georgia

Edited from a more complete article which can be found here.

Annual bluegrass (Poa annua L.) is a problem winter annual weed.  Contrary to its name, both annual (live for one season) and perennial (live for many seasons) populations of annual bluegrass may be found in turf.

Annual bluegrass seed germinates in late summer/early fall once soil temperatures fall below 70° F.  Annual bluegrass may out-compete other turf species during late fall and early spring.  Annual bluegrass often dies from summer stresses but may survive if irrigated – especially the perennial biotypes.

Cultural Control of Annual Bluegrass

Irrigate deeply and infrequently to encourage turfgrass root development and improve the ability of turf to compete with annual bluegrass.  Overwatering, especially in shady areas, may encourage annual bluegrass invasion.

Avoid soil compaction.  Core aerate during active turf growth to encourage quick recovery.  For cool-season grasses, time aerfications before annual bluegrass germinates.

Reduce nitrogen fertilization during peak annual bluegrass germination and periods of vigorous growth.  Fertilizing dormant turfgrasses when annual bluegrass is actively growing may make infestations worse.

Use the proper mowing height, frequency, and equipment for your turfgrass (Table 1).  Raise the turf mowing height during peak annual bluegrass germination.

Mow turfgrass frequently during periods of vigorous growth to prevent scalping.  Returning clippings recycles nutrients to the soil but clippings may need to be removed when annual bluegrass is producing seedheads to reduce the spread of viable seed.

Prevention Using Pre-emergence Herbicides (See Table 2)

Preemergence herbicides may prevent annual bluegrass establishment from seed.  However, preemergence herbicides will not eradicate established plants and will not effectively control perennial biotypes of annual bluegrass from spreading vegetatively.  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.  A second application can be applied in winter to control later germinating plants.  Fall applied preemergence herbicides should not be used if reseeding or resodding is needed to repair areas of damaged turf within several months after herbicide applications.

Several preemergence herbicides used for summer annual weed control will effectively control annual bluegrass in fall and winter (Table 2).  Fall applications of herbicides such as bensulide (Betasan), dithiopyr (Dimension), flumioxazin (Sureguard), oxadiazon (Ronstar, Starfighter), pendimethalin (Pendulum, others), and prodiamine (Barricade, others) may effectively control annual bluegrass.  Indaziflam (Specticle) provides excellent preemergence control of annual bluegrass and also provides early-postemergence control as well.  Indaziflam is only labeled in warm-season turfgrasses but may provide greater application timing flexibility than dinitroaniline herbicides in fall.

Combination herbicide products are also available which may improve efficacy of applications.  These products include oxadiazon plus bensulide (Anderson’s Crab and Goose), oxadiazon plus prodiamine (Regalstar), and benefin plus oryzalin (Team 2G or Team Pro).  Many preemergence herbicides are available under a wide variety of trade names and formulations and turf mangers should carefully read label directions before applications.

Atrazine (Aatrex, Purge, others) and simazine (Princep, WynStar, others) are labeled for centipedegrass, zoysiagrass, St. Augustinegrass and bermudagrass.  Atrazine can be applied to actively growing and dormant centipedegrass or St. Augustinegrass but bermudagrass can be injured if treated while actively growing.  Both herbicides have excellent preemergence activity on annual bluegrass but soil residual is generally shorter (four to six weeks) compared to aforementioned herbicides.  Several atrazine products are restricted use pesticides and turf managers should check labels for further information before use.

Mesotrione (Tenacity) is labeled for use in centipedegrass, perennial ryegrass, St. Augustinegrass (sod production only), tall fescue, and dormant bermudagrass (Table 2).  Mesotrione may be applied during establishment of these grasses (except bermudagrass) and effectively controls annual broadleaf and grassy weeds.  Preemergence applications of mesotrione control or suppress annual bluegrass but postemergence use is ineffective for control of established plants.  Mesotrione may be applied in tank-mixtures with atrazine or simazine on centipedegrass to improve efficacy of applications.

Most preemergence herbicides will provide similar initial efficacy if applied before annual bluegrass germination and 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 soil seedbank.  Retention on leaf tissue can be avoided by irrigating turf immediately after application for effective soil incorporation and herbicide activation.

Preemergence herbicide applications on non-irrigated sites have less potential for residual control, compared to irrigated turf, from product loss, poor soil incorporation, and failure to activate the herbicide.  Practitioners should return clippings on non-irrigated sites to help move potential herbicides remaining on leaf tissue to the soil.  If clippings are collected as part of routine maintenance, practitioners should consider returning clippings until at least half to one inch of rainfall is received.  Granular products may also be applied to non-irrigated sites for better soil incorporation than liquid formulations.  Granular products may be easier to handle and apply with less equipment necessary than sprayable formulations.  Granular herbicides should be applied when morning dew is no longer present to avoid interference from leaf tissue.

Managing Herbicide Resistance

Repeated use of one herbicide chemistry may control annual bluegrass but resistance may develop.  Herbicide resistance is the survival of a segment of the population of weeds following a herbicide dosage lethal to the normal population.  Resistance occurs from repeated use of the same herbicide or mode of action over years and may be a concern with annual bluegrass.

Triazine herbicides, atrazine and simazine, have been repeatedly used for years due to the wide spectrum of weeds controlled as pre- or postemergence treatments in warm-season grasses.  Resistance in weed populations has been reported with these herbicides which may contribute to inconsistent efficacy for annual bluegrass control in turf.  Resistance to sulfonylureas has been reported in numerous weed species and repeated use in turfgrasses may also contribute to resistance in annual bluegrass populations.

Preemergence chemistries, such as the dinitroanalines, (benefin, oryzalin, pendamethalin and prodiamine) may have resistance among weed populations from repeated use over years.  Turf managers should rotate preemergence herbicides from dinitroanilines to other modes of action to minimize resistance in annual bluegrass populations.  Herbicides to consider in rotation programs from dinitroanilines would include indaziflam, ethofumesate, or oxadiazon.  These chemistries offer a different mode of action than dinitroanilines but cost, label restrictions, and turfgrass tolerance may be limiting factors for using these products.  Combination herbicides are also available, such as oxadiazon + prodiamine (Regalstar) and oxadiazon + bensulide (Anderson’s Crab and Goose), with more than one mode of action that effectively control annual bluegrass in turf.

Table 1.  Mowing requirements for commercial turfgrasses.

Mowing Requirements for Turfgrasses
Species Mower Type Height (inches) Frequency (days)
Bermudagrass
    Common Rotary/reel 1 to 2 5 to 7
    Hybrid Rotary/reel 0.5 to 1.5 3 to 4
Centipedegrass Rotary 1 to 2 5 to 10
Perennial Ryegrass Rotary/reel 0.5 to 2 3 to 7
St. Augustinegrass Rotary 2 to 3 5 to 7
Tall Fescue Rotary 3 5 to 7
Zoysiagrass Reel 0.5 to 2 3 to 7

 

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

Common Name Trade Name (Examples) Efficacy
atrazine Aatrex, various E
benefin Balan, others E
bensulide Betasan, others F
dithiopyr Dimension G
ethofumesate Prograss G-E
flumioxazin Sureguard G
indaziflam Specticle E
mesotrione Tenacity F
oryzalin Surflan, others G
oxadiazon Ronstar, others G
pendimethalin Pendulum, others G
prodiamine Barricade, others E
pronamide Kerb E
simazine Princep, others E

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

For more information

Annual Bluegrass Control in Residential Turfgrass

Annual Bluegrass Control in Non-Residential Commercial Turfgrass

+ More