www.sportsturfonline.com26 SportsTurf | August 2013

FieldScience | By Jerad Minnick & Allen Reed

Challenge: Thatch/organic build-up onbermudagrass athletic fields.

Issues challenge is causing: Reduceddurability, including plants growing verticalup through the thatch instead of laterally soit is not as strong and healthy as needed;and thatch breaking down into organic ma-terial is full of fines, creating surface com-paction and slickness.

• Isolated dry spots due to inconsistentrooting

• Increased water requirement for rye-grass overseeding (seed is growing in thatchinstead of in the soil)

• Decreasing ryegrass overseeding dura-bility (seed is growing in thatch instead ofsoil)

Concept solution: Fraze mow to cleanout thatch completely. Thatch managementon bermudagrass is an on-going challenge

for sports field managers. Advancements inbreeding to create more aggressive bermuda-grass varieties create a solution for high traf-fic fields. But conversely, vigorous growthcompounds the challenge of maintainingthatch and organic material build up.

Verticutting, core aeration, and topdress-ing are the accepted maintenance practiceswith which sports field managers addressthatch and organic material build up on allgrass fields (cool or warm season). Accord-ing to data from the International SportsTurf Research Center, a verticutting ma-chine with 3mm blades on 1” centers re-moves 11.81% of the surface area. Coreaeration with 5/8” hollow tines on 2”x 2”spacing removes 7.67%. Thus ultimatelyverticutting and core aeration can not keepwith maintaining the current thatch levels,let alone reduce the amount of thatch and

organic build up taking place on top of abermudagrass athletic field.

INTRODUCTION TO FRAZE MOWING

In 1996, Ko Rodenburg decided thatthe practices of verticutting, core aeration,and topdressing for thatch and organicmanagement on his Kentucky bluegrassand rye fields needed another option. As

Concept to active practice: fraze mowing bermudagrass makes debut

With overseeding andfeeding the fields, thegrass could regeneratequickly, nearly thatchand organic free.

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the parks superintendent for Rotterdam,Netherlands, Rodenburg created a machinethat could remove 100% of the thatch andorganic build up that accumulated each sea-son. At the same time, the machine re-moved the poa annua plants and seedaccumulation while leaving the crown ofthe Kentucky bluegrass and rye grass for re-generation. With overseeding and feedingthe fields, the grass could regeneratequickly, nearly thatch and organic free. Ro-denburg’s fields immediately becamestronger and more durable as the re-growthof the stand was much hardier than theoriginal sword of grass. Additionally, thecompaction potential at the surface was re-duced because the fines from the organicbuild up were cleaned out and the diseasepressure was nearly eliminated with thethatch removal of the thatch. Thus in 1997,fraze mowing with the KORO Field Top-maker was born.

The adaptation of fraze mowing tobermudagrass is more an introduction ofthe entire concept to the United States. A

practice common on fields across Europe toimprove field durability and reduce poaannua, fraze mowing fits naturally intobermudagrass thatch and organic manage-ment. That adaptation became even morenatural this year with the introduction ofthe Universe rotor for the KORO FieldTopmaker. The Universe, designed byImants (makers of KORO) and CampeyTurf Care (of Manchester, UK), is for frazemowing Desso sand-based natural grassfields. The 3/8” blades, aligned on four spi-rals, allow for Desso fields to be frazemowed without damaging or pulling outthe synthetic fibers in the sand. The smallteeth do the same for bermudagrass plants,cleaning off the stolons, thatch, organicbuild up, and leaving the rhizomes of thebermuda exposed in order to regeneratequickly.

Allen Reid and Miles Studhalter at FCDallas Park became the first Americans tocommit to fraze mowing entire fields (frazewhen referencing bermudagrass) to cleanout ryegrass overseeding, thatch, and or-

ganic build up on three fields. In mid-March, Simon Gumbril from Campey TurfCare was on hand in Dallas to oversee theprocess. Also, Joe Pemberton, headgroundsman at Manchester United’s Car-rington Training Ground stopped in to FCDallas Park to observe while in the USA ona vacation.

The 419 bermudagrass was still 95%dormant in March, but a few of the rhi-zomes were showing some green in thefields as they were cleaned off. See photo 1-6 for the results.

The highlight field, the FC Dallas train-ing field, was out of play for 8 weeks,though the field was ready for play in 7weeks. The unseasonably cold spring in theDallas area hampered the re-growth byslowing the 419 bermuda’s exit from dor-mancy, extending the re-generation periodby approximately 2 weeks. But still, theprocess succeeded. According to Reed, “Thefirst day Coach walked back on the pitch hesaid, ‘the field feels strong.’ Now after 2months of daily training, the field has been

Left: Fraze mowing process Middle: Rhizomes exposed after rye, thatch, and organic removal Right Top: First mowing, 2 weeks after fraze mowingRight Bottom: Field 6 weeks after fraze mowing

28 SportsTurf | August 2013 www.sportsturfonline.com

FieldScience

lightly verticut one time to stay ahead of thethatch, and is showing little to no wear.”

Fraze mowing next used when MarylandSoccerPlex Grounds staff cleaned off threefields of Patriot bermudagrass in early June.Because the fields were sprigged only 18months ago, the processes was intended totransition out the ryegrass and promote aquicker transition to full bermudagrass in-stead of cleaning out years of thatch and or-ganic build up. The Patriot bermudagrasswas 30% out of dormancy when cleanedoff, but within 10 days all of the exposedrhizomes were green and responding. A lackof warm weather was again an obstacle forthe SoccerPlex fields, but not to the extentof Dallas. See photos 7-9 for results.

The three SoccerPlex fields that werecleaned off were 100% bermudagrass im-mediately. The non-fraze mowed bermuda-grass fields still were only 80% bermuda(rye being the other 25%) on July 1. Addi-tionally, the removal of only a thin layer oforganic build up on top of the native soilfields now allows water to be absorbed intothe soil faster. Following heavy rains, thefraze mowed fields now soaking in rainmuch faster than before, allow the fields tobe used more.

Also in June, a golf course fairway ofCelebration bermudagrass in North Car-olina was fraze mowed to demonstrate theprocess on active, fully growing bermuda-grass. The Celebration had begun to buildup a thick thatch layer that needed cleanedout (see photos 10-12).

Fraze mowing is a new process to theUnited States turfgrass market. Yet manyintuitive sports turf managers have always

1.THATCH/ORGANIC build-up, June 20122.THATCH/ORGANIC build-up, July 2013 (re-duced by 1 inch)3.FRAZE MOWING Patriot bermudagrass 4.GREEN RHIZOMES prepared to re-generatefrom Celebration bermuda5.GREEN RHIZOMES exposed from fraze mow-ing 6.THATCH BUILD-UP removed from Celebrationbermudagrass7.EXPOSED RHIZOMES following clean out viafraze mowing

1.

2.

3.

4. 5.

6. 7.

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used similar techniques such as scalping, shallow sod cut-ting, and even burning off to remove thatch build-ups.Now those are brought into one practice. The process is avastly different approach to thatch management. It is apractice is not for the faint of heart and can leave a sportsturf manager questioning whether they should have done itor not for the 1st week. But ultimately, the strong grass willprevail.

Albert Einstein said it best: “If you always do what youhave always done, you will always get what you have alwaysgot.” Can fraze mowing bermudagrass become an acceptedpractice in a regular maintenance program to advance thedurability of fields for them to sustain more traffic? That isnow up to the industry to decide. For more on fraze mow-ing bermudagrass, see Jerad Minnick’s blog, http://Grow-ingGreenGrass.Net. n

Jerad Minnick is sports turf manager of the Maryland Soc-cerPlex at the Maryland Soccer Foundation, Boyds, MD. AllenReed is stadium groundsman for FC Dallas.

FIELD 12 following fraze mowing compared to 5 weeks later

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FieldScience

SportsTurf: How will turf managers firstrecognize they have a grub problem?

Dr. Shetlar: Most professional managerswill notice that the turf under their care isnot performing well or is showing signs ofdrought stress at times when soil moisturesare okay. However, inexperienced managersmiss grub populations until the birds or dig-ging animals “show” where the grubs are!Unfortunately, by this time, the grubs areoften third instars and pretty difficult tocontrol with inexpensive products. At thistime, one may have to use Dylox or Arenaand ensure that immediate irrigation fol-lows the application.

Dr. McGraw: Probably more oftenthen not, most turf managers recognizethey have a problem once they have someserious damage signs. Vertebrates likeskunks poking around, raccoons rollingback the turf or birds pecking at the turfare all good signs of grub activity. This ismore likely to be late in the fall and whengrubs are fairly large and capable of caus-ing some damage on their own (i.e., feed-ing on the roots of the plant).

Astute turf managers would probablycue into a general wilty-or yellowing ap-pearance to the turf in earlier in the fall, andfollow this observation up with some sortof soil probing (taking a golf course cup cut-ter to a section of turf and looking for theactual culprits is in my opinion a easy wayto confirm grub presence). Given the work-load of sports turf managers, especiallythose that have many schedule games andactivities on fields in late summer to earlyfall, proactively sampling large areas with acup cutter is probably not feasible. Restrict-

ing sampling to where grubs have been aproblem in the past and in high-valuedareas is a more realistic approach.

ST: What steps do you recommend toeradicate the problem?

Dr. McGraw: Preventive insecticides arestill the number one go to method of con-trol. When neonicotinoids like imidaclo-prid (Merit) came on the market itrevolutionized how we treat for grubs. Be-fore, turf managers had to applied harsherchemicals curatively or after the infestationhad been realized. With products like imi-dacloprid and newer classes like the an-thranilic diamides (Acelepryn), applyingpreventively before egg hatch leads togreater levels of control, since you are deliv-ering a toxin to a much smaller insect (1stinstar larva vs. a 3rd instar). That being said,eradication is not really possible even withchemical controls. Adult beetles are capableof travelling great distances to find your ad-equately watered soils to lay their eggs in.Even with great control in Year 1, someadult beetles will wander in Year 2 fromneighboring sites.

Dr. Shetlar: Late season grub issues fallinto what I call “rescue treatments.” This isan extreme form of curative treatment be-cause the large grubs can be 30 to 40 timesthe body weight of the grub that hatchedout of the egg! Another issue is that thegrubs often stop feeding once they haveachieved their maximum size for the season.

I often talk to Dan Potter in Kentuckyin September and he points out that hisJapanese beetle and masked chafer grubshave turned a yellow white color which in-

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Dealing with grubs:latest recommendationsEditor’s note: We asked two noted academicians, Dr. David Shetlar, professor of entomologyat Ohio State, and Dr. Benjamin McGraw, associate professor, golf & plant sciences at theState University of New York-Delhi, to update us on treating grub problems:

I think that, especially on sports fields, we can min-imize the effects of white grub damage substantiallyby developing a healthy turf stand

— Dr. McGraw

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dicates that they have made all the fat that they aregoing to make for the season and they’ve stopped feed-ing. During this same time, the grubs in Central Ohioare still very white and still feeding! Why is this impor-tant? While many insecticides have contact activity (ab-sorbed through the exoskeletons), the primary modeof getting insecticides into the insects is by ingestion!In short, the closer you get to the transition zones, theearlier that annual white grubs may stop feeding forthe summer/fall season.At present, products containing trichlorfon

(=Dylox) or clothianidin (=Arena and Aloft) seem tohave the best chance of killing large, third-instargrubs—if they are feeding! Both products tend to killthe grubs within 3 to 5 days which will also stop anyanimal digging. In our field tests, the other neonicoti-noids, imidacloprid (=Merit) and thiamethoxam(=Meridian) will kill third instar grubs, but they oftentake 10 to 14 days. I also commonly recommendspreading Milorganite fertilizer (made from humansewage sludge which no longer contains any heavymetal contaminations) over the area where animals aredigging as this will chase them away for a week or sowhile the insecticide is doing its thing.

ST: What are your recommendations for prevent-ing a future reoccurrence of grubs in the same turf?

Dr. Shetlar: Most of the registered grub controlproducts (other than Duocide which contains carbaryland bifenthrin) can be used as preventives. This gen-erally means to apply them before egg hatch of the an-nual white grubs. In most of the cool-season zones, thiswould be applied by mid-July. In my grub efficacychart, imidacloprid, thiamethoxam, clothianidin (theneonics) all give 90% or better control if applied inJune, July into mid-August. If you move into May, im-idacloprid and thiamethoxam seem to run out of ef-fective residuals.Of course, the new insecticide is chlorantraniliprole

(=Acelepryn) which can be applied in April throughearly August and get excellent grub control! For sportfield managers, this should be a product of choice as italso has the most benign environmental footprint. It isalso the “least toxic” of the insecticides to mammalswhich is a plus in sport field situations!Whether to treat or not can often be answered by

the research that was done by Mike Villani when hewas at Cornell (unfortunately he passed away while stilla relatively young turfgrass entomologist). He surveyedlots of golf courses and lawns in New York over severalyears. He found out that if an area of turf had a dam-aging population of grubs, it was in the 80% risk levelof repeating a damaging population the following year.In short, treat areas where grub damage has been pre-viously noted.

Dr. McGraw: I think that, especially on sportsfields, we can minimize the effects of white grub dam-age substantially by developing a healthy turf stand: allthe things you learn in Turf 101: adequate (not exces-sive) nutrients and water, minimize compaction, im-prove drainage as much as possible, and mostimportantly, develop a deep and extensive root system.A healthy stand will definitely tolerate more white

grubs without showing signs of damage than a stressedstand. Also, spend a day or two scouting out and map-ping infestations. Take a golf course cup cutter, regu-larly sample (in certain grid like patterns), break apartthe core in 1/4s and visually assess whether grubs arepresent. Try to identify what species of grub it is bylooking at the raster pattern (row of spines on theirbutts). But most of all: keep good records. Grubs tendto appear in the same areas year after year. Find outwhat it is about that area that causes them to return:adult food sources, under-watered, over-watered,shaded, full sun, turf species?

ST: Do you recommend using nematodes to com-bat grubs? Why or why not?

Dr. McGraw: Nematodes may provide both shortand long term suppression of white grubs and defi-nitely have a place in grub management. You need tobecome educated in their proper use and applicationthough. These are living organisms and need to behandled with care. There are some major hurdles intheir adoption in many areas, namely their price andthe product supply chain. However, as is the case inmany states like NY where we have a ban of chemicalpesticides on primary school grounds and daycares,this may be one of the handful of options that a sportsfield manager has in controlling white grubs. I hopethat their adoption is greater in the future because itis an environmentally responsible approach. However,it is a case of economics right now. There needs to bea greater interest or demand from turf managers be-fore the market can respond to the supply issues.Only then will the price come down.

Dr. Shetlar: I only recommend the insect parasiticnematodes for organic lawn care and for homeownerswho wish to use non-pesticide techniques. They arestill relatively expensive to use and you need toarrange with the supplier to ship the nematodes at thetime you are going to apply them. In short, you haveto use fresh nematodes! And, when you get them,they have to be applied quickly, with lots of pre-irri-gation and post-irrigation. Even with the best of ap-plications, it has been my experience that they willfail about 25 to 40% of the time. However, when theywork, they often work very well! Bottom line, theyare expensive, difficult to use and the risk of failure isrelatively high. n

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