Virginia Turfgrass Journal - May / June 2016

Journal of the Virginia Turfgrass Council

Twelfth Annual Digest of Turfgrass Research in Virginia Science-Based Information for the Management of Golf Courses, Sports Fields Lawns and Sod Farms

May/June 2016

Journal of the Virginia Turfgrass Council | May/June 2016

Twelfth Annual

Digest of Turfgrass Research in Virginia Upcoming Events 9 Mark Your Calendars Now For These Must-Attend Events

Summaries of More Research Projects 24 Organic Amendments Improve Tall Fescue Lawn Performance in Urban Soil

Research Reports

26 The Heating Characteristics of Tall Fescue/ Kentucky Bluegrass and Bermudagrass Sods

12 Impact of Fraze Mowing on Spring Dead Spot Severity and Recovery

27 Preemergence Crabgrass Control in Bermudagrass

14 Effects of Common Turfgrass Insecticides on Earthworms

28 Preemergence Crabgrass Control in Tall Fescue

18 Coastal Sandbur — a Troublesome Grassy Weed

29 New Hands-Off Approach for Monitoring Drought Stress to Creeping Bentgrass and Bermudagrass

20 Dollar Spot Suppression with Iron Sulfate 22 Spring Dead Spot Control Using Fungicides

Departments 6 8 9 10 29 30

President’s Message from Rick Owens, CGCS Director’s Corner from Tom Tracy, Ph.D. Virginia Tech’s Turfgrass Researchers VTF Report from Betty Parker Advertiser Index Turfgrass Calendar

Virginia Turfgrass Council (VTC) serves its members in the industry through education, promotion and representation. The statements and opinions expressed herein are those of the individual authors and do not necessarily represent the views of the association, its staff, or its board of directors, Virginia Turfgrass Journal, or its editors. Likewise, the appearance of advertisers, or VTC members, does not constitute an endorsement of the products or services featured in this, past or subsequent issues of this bimonthly publication. Copyright ©2016 by the Virginia Turfgrass Council. Virginia Turfgrass Journal is published bimonthly. Subscriptions are complimentary to members of VTC. POSTMASTER: Send change of address notification to VTC, P.O. Box 5989, Virginia Beach, VA 23471. Postage guaranteed. Third-class postage is paid at Nashville, TN. Printed in the U.S.A. Reprints and Submissions: Virginia Turfgrass Journal allows reprinting of material published here. Permission requests should be directed to VTC. We are not responsible for unsolicited freelance manuscripts and photographs. Contact the managing editor for contribution information. Advertising: For display and classified advertising rates and insertions, please contact Leading Edge Communications, LLC, 206 Bridge Street, Franklin, TN 37068-0142, (615) 790-3718, Fax (615) 794-4524. Deadlines are the first of the month prior to the following month’s publication. (Example: August 1 for the September issue.)

4 | Virginia Turfgrass Journal May/June 2016 www.vaturf.org

President’s Message

One More Busy Summer

As

I write this message, we are in the midst of yet another hot, humid and challenging summer. For most turfgrass managers, summer is an extremely busy time with long hours and much time away from family. Sometimes it is hard to achieve a healthy work versus life balance, but it is important to do so. Make sure to make time for friends and family.

One opportunity to meet up with friends will occur with the annual Bob Ruff Jr. Memorial Golf Tournament, to be held on September 12 at Wintergreen, VA. Proceeds will go to turf research at Virginia Tech. Please take the opportunity to enjoy the cooler mountain air and resume friendships while supporting our industry. Last year’s event was a great success. This year, we will be again on the Devil’s

Rick Owens, CGCS 2016–2017 President

Knob Course high up on Wintergreen Mountain. Make your foursome early so that you are assured a spot!

Rick Owens, CGCS

2016–2017 VTC President Note from our publisher, Leading Edge Communications: Leading Edge sincerely apologizes for how late this issue of the Journal is in reaching you. Our managing editor, Liz Nutter, was seriously ill for three months this spring and early summer.

She is now well on her way to recovery, and we intend to get right back on schedule with publishing this important magazine for the members of the VTC.

Thank You to Our 2016 Platinum Members!

• Agronomic Lawn Management • Aspen Golf • Henrico County • James Madison University • James River Ground Management • Landscape Supply • Liberty University • Longwood University • Roanoke City • SiteOne Landscape Supply • Stafford County • TruGreen • Virginia Green 6 | Virginia Turfgrass Journal May/June 2016 www.vaturf.org

Director’s Corner

An Outstanding Day of Pesticide Recertifications

The

end of June marked the end of another season of pesticide recertifications. From the Shenandoah Valley to northern Virginia to the Atlantic Ocean, more than 1,000 professionals attended our classes to increase their knowledge and to stay in compliance with pesticide licensing requirements. These classes were the result of many volunteers working behind the scenes.

Allow me to focus on the recertification class we held in the City of Hampton on June 14 and highlight persons as examples of the tremendous partnerships that enabled us to serve the industry through these classes.

Beth Haines — Beth was the behind the scenes, go-to person who made everything possible. In addition to hours of unseen work, she presented an update on right-of-way pesticide issues from the perspective of a person who supervises the maintenance of many miles of such areas.

Staff of the City of Hampton’s Park and Recreation Department — These persons directed participants to the meeting room and ensured that the room was properly set.

Staff of the Hampton Coliseum — They ensured that our needs were met in the midst of extensive preparations for high school graduations.

Rick Viancour — Rick set the bar very high for meeting rooms on the peninsula by ensuring that we had great locations in the Williamsburg area before we moved to Hampton.

Robert Christian — This VDACS inspector always goes out of his way to ensure that persons know the rules and regulations!

Jeff Derr, Ph.D. — As always, Dr. Derr went the extra mile and presented a very high-quality update on weeds.

8 | Virginia Turfgrass Journal May/June 2016 www.vaturf.org

Tom Tracy, Ph.D. VTC Executive Director

Barbara Garvis — In addition to presenting practical steps to keeping pesticides out of Virginia’s waters, Barbara presented partnership opportunities between the Elizabeth River Project and turfgrass professionals.

Ray Funkhouser — Ray’s “can do!” attitude and wealth of knowledge enriched all who attended!

Jimmy Viars — Jimmy did a great job of transforming a very important (but sometimes difficult) subject into terms all could relate.

What was the result of the hard work by all the above persons? In addition to providing a class that allowed persons to remain legal, we truly served the industry. As an example, here is an email I received the day after our Hampton program: Good afternoon, Tom. I just wanted to say thanks and show my appreciation for the last pesticide recertification course held in Hampton on the 14th. I have been in the pest-control industry for over 20 years and am currently involved with the stormwater regulatory industry as well. It was nice to hear your presenters, including yourself, speak on the importance of utilizing caution when applying pesticides and fertilizers in and around stormwater conveyance systems and natural waterways. The philosophy was reiterated throughout the day and I really thought you are leading the industry in the correct direction.

Thanks again for a great day of presenters and for indicating the importance of stormwater rules and regulations to the folks who really work hard every day throughout our region. Great job, Tom! Keep up the good work!!!

We are making plans for 2017 recertification classes.

One exciting development is the morphing of two of our programs into conferences: Come to the Bay and Come to the Valley. Details about all of our programs are on our web site (www.vaturf.org). c

Upcoming Events Virginia Turfgrass Journal is the official publication of The Virginia Turfgrass Council P.O. Box 5989 Virginia Beach, VA 23471 Office: (757) 464-1004 Fax: (757) 282-2693 vaturf@verizon.net Published by Leading Edge Communications, LLC 206 Bridge Street Franklin, Tennessee 37064 (615) 790-3718 Fax: (615) 794-4524 Email: info@leadingedgecommunications.com Editor Mark Vaughn, CGCS VTC OFFICERS President Rick Owens, CGCS Laurel Hill Golf Club (703) 674-6934 Vice President Scott Woodward Woodward Turf Farms (540) 727-0020 Treasurer Michael Skelton Culpeper County (540) 727-3412 Past President Fredrick Biggers, CGCS Wintergreen Resort (434) 325-8252 VTC DIRECTORS Steve Glass Tony Montgomery Marc Petrus Jesse Pritchard Michael Skelton Rick Viancour, CGCS Jimmy Viars, CGM Craig Zeigler ­ VTC ADVISORY MEMBERS OF THE BOARD Mike Goatley, Ph.D. (Chair) Shawn Askew, Ph.D. Jeffrey Derr, Ph.D. Erik Ervin, Ph.D. David McCall Ph.D. Executive Director/ Director of PROGRAMS Tom Tracy, Ph.D. (757) 464-1004 Virginia Turfgrass Foundation Betty Parker (757) 574-9061

Mark Your Calendars, and

Plan To Be Here!

September 12, 2016 Bob Ruff Jr. Memorial Research Golf Tournament

Wintergreen Resort — Devil’s Knob Wintergreen, VA

January 30 – February 2, 2017 Mid-Atlantic Turfgrass Expo

Fredericksburg Expo & Conference Center Fredericksburg, VA

Virginia Tech’s Turfgrass Researchers Shawn D. Askew, Ph.D.

Mike Goatley Jr., Ph.D.

Virginia Tech 435 Old Glade Road Blacksburg, VA 24061 (540) 231-5807 saskew@vt.edu

Virginia Tech 420 Smyth Hall, CSES Dept.

Blacksburg, VA 24061 (540) 231-2951 goatley@vt.edu

Jeffrey F. Derr, Ph.D.

David McCall, Ph.D.

Virginia Tech Hampton Roads Agricultural Research Station 1444 Diamond Springs Rd. Virginia Beach, VA 23455 (757) 363-3912 jderr@vt.edu

Virginia Tech 435 Old Glade Road Blacksburg, VA 24061 (540) 231-9598 dsmccall@vt.edu

Erik H. Ervin, Ph.D.

Thomas P. Kuhar, Ph.D.

Virginia Tech 339 Smyth Hall, CSES Dept.

Blacksburg, VA 24061 (540) 231-5208 ervin@vt.edu

With Support from:

Virginia Tech Dept. of Entomology 216 Price Hall 170 Drillfield Drive Blacksburg, VA 24061 (540) 231-6129 tkuhar@vt.edu

Journal of the Virginia Turfgrass Council

|9

VTF Report

Green Industry

Survey Brewing!

S

ome of you may have heard there is a new green-industry survey brewing out there. The last one, spearheaded by the turfgrass industry and funded entirely through the Virginia turfgrass industry, was back in 2004. We are well past due for another! A state-funded survey through VDACS for sectors of the agriculture industry (such as forestry, vineyards, turfgrass and others) was being offered on a rotating basis every five years, and

turfgrass was due its funding for a new survey in 2009. That, of course, was when the recession dried up all funds for this, and we were denied this muchneeded opportunity.

With a cooperative effort from all of you, however, Virginia can update the 12-year-old data to show our citizens and legislators the magnitude and influence of the turfgrass industry in Virginia’s economy. We ask that each of you consider the importance

Betty B. Parker VTF Manager

in taking the time to complete the survey as your part in keeping our industry strong.

The Virginia green-industry survey will go live during summer 2016. A link to the electronic survey will be embedded in emails that will go out to each industry area: airports, cemeteries, churches, golf courses, highways, home lawns, nurseries, parks, schools, sod farms and sports turf. The data collection will wrap up by December 2016. During the survey administration period, you may be asked to complete the survey by stakeholders in your industry.

Survey administration will be managed by Amy Thelk and Kitti Robinson. Amy has a Ph.D. in Assessment and Measurement and currently holds the position of Director of Assessment at James Madison University’s College of Education. She has extensive experience with survey and evaluation work in her community, for federal grants and with several major national testing companies.

Kitti is working on her doctoral degree in Educational Psychology and currently holds a master’s degree.

She has extensive experience in data collection, measurement and analysis of human behavior and will be assisting Amy with the data collection and analysis components of the survey.

Don’t miss this opportunity to help us help you! Please make the time to complete this survey! Thank you all in advance. You are a great group of people, and we need this documentation. c A special thanks to Amy Thelk and Kitti Robinson, who contributed much of the information in this article.

10 | Virginia Turfgrass Journal May/June 2016 www.vaturf.org

Research Report

Impact of Fraze Mowing on Spring Dead Spot Severity and Recovery Virginia Tech Researchers: Camden Shelton, Graduate Research Assistant; Jordan Booth, Graduate Research Assistant; and David McCall, Ph.D., Research Associate Research Cooperator: Rodney Hopkins, Innovative Turf Application and Consulting, and Lee Miller, Ph.D., University of Missouri

H

ybrid bermudagrass (Cynodon dactylon) is one of the most desirable turfgrass species for sports fields and golf course playing surfaces in Virginia because of its aggressive growth habits, traffic tolerance, uniformity and color.

Spring dead spot (SDS), caused by the fungal pathogens Ophiosphaerella korrae and O. herpotrica, is the most destructive disease of bermudagrass in Virginia and one of the biggest limiting factors to the success of hybrid bermudagrasses as playing surfaces.

As the name implies, symptoms of SDS first appear in the spring, when bermudagrass resumes growth from its normal winter dormancy. As the turf breaks dormancy and begins to turn green, circular patches or rings of turf appear to remain dormant and eventually collapse to the ground and die. The disease is usually most severe after the turf is three to five years old as fungal populations and thatch accumulation increases. The pathogen survives in the thatch and infects the plants in the late summer and fall. Hybrid bermudagrasses that tend to produce excessive thatch are more prone to the disease.

A unique characteristic of SDS is that the pathogens do not kill bermudagrass directly. These fungi attack the roots, rhizomes and stolons of bermudagrass in the fall and winter and increase the bermudagrass’ susceptibility to cold and freezing injury.

Fall fungicide applications, properly timed cultural practices and coldtolerant bermudagrass varieties form an integrated approach to managing the disease.

Cultural practices are a vital part of an integrated pest management program. Cultural practices include but are not limited to proper mowing and watering practices, core aeration, sand topdressing and vertical mowing. Most of these practices are designed to manage thatch in the profile. The inherent problem with these practices is the disruption to the playing surface, and a common result is an insufficient thatch-management program that never really keeps up with the excessive thatch produced by hybrid bermudagrasses and other varieties.

A new technique being employed is a process known as “fraze mowing” or “fraise mowing.”

Fraze mowing and the equipment used to fraze mow was developed by Ko Rodenburg of the Netherlands for the renovation of cool-season turfgrass fields. Rodenburg developed a rotary tiller-type machine (KoRo) that takes off the top layer of the turf, leaving just the roots, rhizomes and some crowns, depending on the height of cut. The debris, which can be utilized as compost or sprigs in bermudagrass applications, then comes out on a conveyer belt located on the side of the machine.

Fraze mowing helps promote new growth and also eliminate thatch and organic buildup on the surface. It also helps decrease weed seed and some cases of black layer. This process is very aggressive (not applicable in all situations), and it takes some time to recover. The noted benefits of thatch removal after fraze mowing led to the question amongst turf researchers: Can fraze mowing reduce SDS inci-

12 | Virginia Turfgrass Journal May/June 2016 www.vaturf.org

dence and/or severity and aid in the recovery in hybrid bermudagrass?

Our research

A split-plot research trial was designed to compare SDS occurrence, severity and recovery in hybrid bermudagrass plots under different fraze mowing depths and nitrogen sources. The trial was established on a ‘Patriot’ hybrid bermudagrass soccer field at the Striker Park, West Creek Complex in Richmond, VA. Fraze mowing occurred on May 29, 2015, and again on June 24, 2016, using a KoRo Imants Field Top Maker (Macclesfield, Cheshire, United Kingdom). Fraze-mow treatments consisted of 0, 4 and 8 mm depths.

Plots received weekly applications of 0.5 pounds of nitrogen for six weeks following fraze mowing, in the form of ammonium sulfate (21-0-0) or urea (46-0-0).

The plots were rated weekly for bermudagrass recovery, SDS recovery and overall turf quality. Spring dead spot severity, incidence and percent disease were rated in June 2016 after overseeded ryegrass was transitioned.

Plots are receiving weekly fertility again in 2016 following the June 24 fraze mow, and they are being rated for recovery. Disease ratings will be collected in late spring of 2017.

Our results to date

After one season, fraze mowing at a depth of 8 mm reduced the incidence (number of SDS patches), severity of patch destruction and overall diseased area compared to the nonfraze-mowed control, when both were

Photo 1. Fraze mowing is an aggressive cultural and renovation practice. Full recovery usually takes six to eight weeks, but surfaces may be playable in as little as two weeks.

fertilized with urea. Fraze mowing at a depth of 4 mm compared favorably with both the 0 mm and 8 mm depths.

Turf-quality reflectance mapping in 2016 showed that split-plots treated with ammonium sulfate were inadvertently impacted by irrigation nonuniformity and were removed from our analysis. Plots treated with urea had higher overall quality than those

Photo 2. Reduction of spring dead spot occurrence and severity was statistically significant between the 8 mm and 0 mm frazemow depths.

treated with ammonium sulfate, but this is attributed to the non-uniform irrigation instead of nitrogen source.

Plots recovered from fraze mowing in 2015 within four weeks and had higher overall density and quality than non-fraze-mowed bermudagrass by six weeks after mowing. Recovery was faster at the 4 mm depth than 8 mm, but the more aggressive depth had

a greater impact on SDS the following spring.

Although more research is needed to validate these results, our data suggest that fraze mowing at a depth of 8 mm can reduce SDS severity and incidence-impacted ‘Patriot’ bermudagrass playing surfaces. Data collection will continue throughout 2016 and in spring 2017. c

Journal of the Virginia Turfgrass Council

| 13

Research Report

Effects of Common Turfgrass Insecticides on Earthworms Virginia Tech Researchers: Sudan Gyawaly, Graduate Student; Curt Laub, Research Associate; and Tom Kuhar, Ph.D., Professor, Department of Entomology Research Sponsor: Virginia Turfgrass Foundation

I

nsecticides are commonly applied in turfgrass systems to primarily control white grubs and to maintain a good-quality turf. The most common insecticides applied on Virginia turfgrass include imidacloprid (Merit), chlorantraniliprole (Acelepryn), clothianidin (Arena) and trichlorfon (Dylox) (see Figure 1). Additional insecticides used in Virginia include thiamethoxam (Meridian), dinotefuran (Zylam) or combination products such as clothianidinplus bifenthrin (Aloft).

However, because many of these insecticides have a broad spectrum of activity and persist for a long period in soil, there is concern among people about their negative impact on nontarget organisms, including earthworms, which play an important role in the soil function of litter breakdown, soil fertility and soil microstructure. Although all insecticide products

are evaluated for their toxicity to the “red wriggler” compost worm (Eisenia fetida) in the laboratory as part of the ecotoxicological-testing requirements of the U.S. EPA for pesticide registrations (Table 1), such tests may not exactly represent the actual impact of these insecticides to other species of earthworms that typically inhabit the soil under turfgrass. The EPA Ecotoxicology Tests are only a gauge of potential negative impact on nontarget organisms.

Our research

Therefore, in 2015, we conducted a field study in Virginia to determine the effects of various turf insecticides on Lumbricus terrestis L. Although an introduced species from Europe, this is the dominant earthworm found in turfgrass in the Mid-Atlantic U.S., including Virginia (Photo 1).

Figure 1. The most widely used insecticide products on Virginia turfgrass, based on a survey we conducted in 2014 at the Virginia Tech Turfgrass Conference (Laub 2016).

14 | Virginia Turfgrass Journal May/June 2016 www.vaturf.org

Three separate field experiments were carried out during the spring, summer and fall of 2015 at the Virginia Tech Campus Golf Course in Blacksburg, VA, where the soil is a Groseclose loam, and the grass composition is a mixture of fescues, ryes, annual bluegrass and bermudagrass.

Treatments used in the field experiments included several commonly used insecticide products at highlabeled application rates, plus a water control (Table 2).

For spring and summer experiments, insecticides were applied on plots (5' × 5' size) arranged in a completely randomized block design, with four replications of each treatment.

For spring and summer experiments, all liquid-insecticide treatments were applied as foliar sprays using a CO2 backpack sprayer. The backpack sprayer was equipped with 4,8002VS

Product

Active ingredient (AI)

Designated toxicity to red wigglers

Acelepryn 1.67SC

chlorantraniliprole

Acute toxicity

Arena 50 WDG

clothianidin

Super toxicity

Zylam (Safari) 20SG

dinotefuran

Acute toxicity

Merit 75WP

imidacloprid

Acute toxicity

Aloft GC SC

clothianidin plus bifenthrin

Extreme toxicity

Meridian 25 WG

thiamethoxam

No toxicity

Dylox 6.2 G

trichlorfon

Moderate toxicity

Table 1. List of common turf insecticide products and their EPAdesignated toxicity to earthworms, based on lab bioassays with the “red wriggler” compost worm, Eisenia fetida.

stainless steel spray tips and calibrated to deliver 20 gpa at 40 psi. The granular insecticide treatment of trichlorfon for each plot was mixed with 1 lb. of sand to ensure uniform coverage over the plot.

For the spring field experiment, insecticides were applied to the turf plots on May 9. Earthworms were sampled by using a mustard-powder suspension method. Two weeks after the treatments were applied, an 8"diameter PVC pipe was inserted into the ground to the depth of about 1.2" in each plot, and one liter of a mustard-powder suspension (0.35 ounce of ground yellow mustard) was mixed in one liter of water and poured into the PVC frame to agitate any earthworms in the soil and bring them to the surface. Within five minutes after application, all earthworms that moved to the soil surface were recorded.

In the summer experiment, all treatments were applied to the plots on August 17 (except trichlorfon, which was applied on September 23).

Rather than the mustard extraction technique used previously, earthworms were sampled on October 9 by cutting two turf plugs per plot to a depth of 3.9" with a 4.2"-diameter golf cup- cutter.

A third field experiment was conducted at four different locations at the Virginia Tech Campus Golf Course in fall 2015. Treatments were applied on October 9 to individual plot sizes of 2' by 2' at each location.

Insecticide treatments were applied as foliar sprays using a watering can with one gallon of water. Granular insecticide was applied by following the method similar to spring and summer treatment. There were four replicates (at four different locations). Earthworms were sampled on October 12 (three days after treatment) using the golf cup cutter technique described above. All data were tested for normality and analyzed using analysis of variance procedures in JMP. Tukey’s HSD test was used to compare means among different treatments.

Research results to date

In all of the experiments, the earthworm species found was predomi-

Photo 1. Lumbricus terrestris, the most common earthworm found in Virginia turfgrass systems.

Treatment

1 2 3 4 5 6 7 8

Product Acelepryn 1.67SC Arena 50 WDG Zylam (Safari) 20SG Merit 75WP Aloft GC SC Meridian 25 WG Dylox 6.2 G Untreated Check

Active ingredient

Rate (lbs. AI per acre)

Amount product per acre

Amount product in 0.75 gal. water

chlorantraniliprole

0.208

16.0 fl. oz.

4.46 ml

clothianidin

0.4

12.8 oz.

3.4 g

dinotefuran

0.54

imidacloprid clothianidin plus bifenthrin

0.4 0.33 0.16

thiamethoxam

2.7 lb.

(43.2 oz.)

8.6 oz.

11.58 g 2.27g

19.0 fl. oz.

5.3 ml

0.266

17.0 oz.

4.52 g

trichlorfon

8.1

130.7 lb.

34.0 g/ plot:

—

—

—

—

Table 2. List of insecticides and rates used in the study.

nantly L. terrestris. There was no significant effect of treatment on densities of earthworms found in the turfgrass in any of the experiments (P > 0.05; Table 3, page 16).

Our field experiments indicated that none of the tested insecticides significantly decreased the abundance

of L. terrestris earthworms in turfgrass within a few days after application. Making conclusions on ecological significance from this singletime, mortality-based study would be impetuous. However, our study does suggest that the results of insecticide toxicity observed in the laboratory Journal of the Virginia Turfgrass Council

| 15

Research Report continued

may not necessarily be indicative of the actual field situation and that a single-time application of white grub insecticide-control products might not be as toxic to earthworms as one might think.

Several factors — including concentration dilution and microbial breakdown of the insecticides — can occur in the field that are often not factored into lab bioassays. More field-level research into the actual environmental

impact of insecticides on earthworms is needed. Sub-lethal impacts on the worms or complex multi-species interactions may also be impacted and are difficult to assess. c

Treatments

Field Trial 1 — Number of earthworms (Mean ± SE) per sample 05/09/15 – 05/21/15

Acelepryn 1.67SC

3.25±1.11

2.5±0.75

4.25±1.24

Arena 50 WDG

2.50±0.29

1.25±1.08

2.25±0.89

Zylam (Safari) 20SG

1.75±0.63

4.25±0.96

5.25±0.96

Field Trial 2— Number of earthworms (Mean ± SE) per sample 08/17/15 – 10/09/15

Field Trial 3 — Numbers of earthworms (Mean ± SE) per sample 10/09/15 – 10/12/15

Merit 75WP

2.00±0.71

2.00±0.70

4.50±0.90

Aloft GC SC

2.50±0.29

4.00±1.41

7.25±1.55

Meridian 25 WG

0.75±0.48

3.25±1.55

6.25±1.34

Dylox 6.2 G

1.50±0.50

2.50±0.75

6.25±3.37

Untreated check

2.25±0.85

5.25±1.43

8.50±2.01

Table 3. Effect of different insecticide treatment on abundance of earthworms in the field study.

16 | Virginia Turfgrass Journal May/June 2016 www.vaturf.org

Research Report

Coastal Sandbur — a Troublesome Grassy Weed

sandbur is a summer annual grass that, under certain environments, may persist as a short-lived perennial. It has long, narrow leaves (blades up to 8" long and about 1/4" wide, with a short hairy ligule). During summer and early fall, it produces seedheads with spiny burs. These spines can be quite painful if you step on the plant barefoot. Coastal sandbur tends to be found in sandy soils, although it can grow in other soil types.

There is a winter annual broadleaf weed called lawn burweed or spurweed (Soliva sessilis), but this plant may also be called sandbur. This broadleaf weed will germinate in fall and flower in spring, forming spine-tipped burs.

So we ask the caller, “Is the weed you are calling about a grass or a broad-

Virginia Tech Researchers: Jeffrey Derr, Ph.D., Professor of Weed Science, and Adam Nichols, Research Assistant, Hampton Roads Ag. Research and Extension Center, Virginia Beach Research Sponsors: The Virginia Turfgrass Foundation and the Virginia Turfgrass Council

A

grassy weed that can be a significant problem in turfgrass is coastal sandbur (Cenchrus incertus, also listed as Cenchrus spinifex).

First, we want to address an issue that

we often have to answer. When we get a call about controlling sandbur, we have to ask the caller some questions to make sure we both are talking about the same weed species. Coastal

Treatment

Rate (lb. ai/A)

Number of sandbur plants at 1 month after application

Shoot fresh weight reduction at 1 month after application

Nontreated

—

22.8

Pendulum AquaCap

3.0

Barricade 4L

Treatment

Rate (lb. ai/A)

Number of applications

Percent control 1 month after 2nd application

0

Nontreated

—

—

—

2.0

78

Monument

0.025

2

50%

0.75

1.7

93

Revolver

0.04

2

51%

Specticle FLO

0.05

3.7

71

Pylex

0.02

2

100%

Ronstar 2G

3.0

4.3

69

Acclaim Extra

0.13

1

100%

Dimension 2EW

0.5

2.6

98

Tenacity

0.25

2

25%

Tenacity 4L

0.25

16.2

41

MSMA

2.0

2

99%

Table 1. Preemergence control of coastal sandbur.

Table 2. Trial 1 — Postemergence control of coastal sandbur.

Photo 1. Coastal sandbur plant.

Photo 2. Coastal sandbur seedhead (painful burs!).

18 | Virginia Turfgrass Journal May/June 2016 www.vaturf.org

leaf weed? When do you see the burs, in spring or in summer/fall?” The answers guide us as to whether the caller is asking about coastal sandbur or lawn burweed. This article will focus on coastal sandbur, the grassy weed.

options. We suspect, though, that erratic germination of coastal sandbur may necessitate postemergence treatments to control escapes later in the season. Acclaim Extra and Pylex are very effective for controlling emerged coastal sandbur and would be control

Our research

We have been evaluating chemical control options for this weed. One area that we have investigated is preemergence control of this weed. In this trial, we evaluated commonly used turf crabgrass preventers.

We have also been investigating postemergence control of this weed.

We added a nonionic surfactant to Monument and Tenacity treatments, while we added a methylated seed oil to the Pylex and Drive treatments.

Research results

In our preemergence trials, Dimension at 0.5 pounds active ingredient per acre (lb. ai/A) and Barricade at 0.75 lb. ai/A gave excellent control (over 90%) of this weed (Table 1).

Pendulum at 3 lb. ai/A, Specticle at 0.05 lb. ai/A and Ronstar 2G at 3 lb. ai/A gave fair to good control in the preemergence trials. Tenacity at 0.25 lb. ai/A reduced the sandbur stand but did not provide acceptable control following a preemergence application.

In our postemergence trials, Acclaim Extra at 0.13 lb. ai/A applied once, or two applications of Pylex at 0.025 lb. ai/A or MSMA at 2.0 lb. ai/A, gave excellent postemergence control of coastal sandbur (Tables 2 and 3).

We counted seedheads in the second postemergence trial. If allowed to grow, sandbur can produce a lot of painful burs! Both Acclaim Extra and Pylex gave excellent control of the burs. Applications of Monument at 0.025 lb. ai/A, , Tenacity at 0.25 lb. ai/ A and Image at 0.38 lb. ai/A, injured coastal sandbur, while Drive at 0.75 lb. ai/A did not control this weed.

The herbicides that we commonly apply for preemergence crabgrass control will also control coastal sandbur, with Barricade and Dimension appearing to be very good control

options in cool-season turf. Where labeled, MSMA is an effective postemergence treatment for control in turf. Additional research is needed to increase the available control options for emerged coastal sandbur in warm-season turf species. c

Treatment

Rate (lb. ai/A)

Number of applications

Percent control 1 month after 2nd application

Number of burs 1 month after 2nd application

Nontreated

—

—

—

339

Monument

0.025

2

27%

331

Image

0.38

1

40%

275

Acclaim Extra

0.13

1

100%

0

Pylex

0.02

2

93%

6

Tenacity

0.25

2

17%

390

Drive

0.75

1

0%

338

Table 3. Trial 2 — Postemergence control of coastal sandbur.

Journal of the Virginia Turfgrass Council

| 19

Research Report

Dollar Spot Suppression with Iron Sulfate Virginia Tech Researchers: Camden Shelton, Graduate Research Assistant; David McCall, Ph.D., Research Associate; and Erik Ervin, Ph.D., Professor

C

reeping bentgrass is commonly used on golf course greens, fairways and tees in temperate climates. Dollar spot, the most common disease of creeping bentgrass, degrades foliage by creating small, silver-dollar-sized depressions of dead turf that may persist throughout the winter. Fungicides are frequently applied throughout the growing season to prevent disease. The number of fungicides used to suppress dollar spot has dwindled because of government regulations, emergence of resistant pathogen populations and failure to provide consistent control.

Our research

Researchers have shown that various cultural strategies can suppress dollar spot. Previous research at Virginia Tech has shown that iron sulfate can effectively suppress the dollar spot pathogen in cultured laboratory studies and under normal field growing conditions. This discovery is being

expanded in 2016 to address whether the incorporation of iron sulfate can reduce the total needs of chlorothalonil (a broad-spectrum fungicide) throughout the growing season.

Trials are underway on ‘007’ creeping bentgrass putting greens at the Turfgrass Research Center and on ‘L-93’ creeping bentgrass fairways at the Glade Road Research Facility, both in Blacksburg, Virginia. Each study is replicated on a green and fairway.

Dollar spot infection centers, visual estimation of percent disease and visual estimation of turf quality are being collected twice weekly throughout the season. Cumulative disease-progression data will be used to estimate the role of iron sulfate throughout the growing season.

One study investigates whether the use of iron sulfate can reduce chlorothalonil rates applied biweekly, while maintaining adequate dollar spot suppression. Five rates of chlorothalonil (0, 1, 2, 3 and 4 fl. oz./1,000

ft2 Daconil WeatherStik®, Syngenta Professional Products) are being applied to plots treated with iron sulfate (1 lb./1,000 ft2, 20% ferrous sulfate heptahydrate) or untreated controls.

Very early indications show that the use of iron sulfate may result in a substantial chlorothalonil rate reduction to maintain bentgrass below an acceptable threshold. A truer estimation of chlorothalonil reductions will not be available until later in the season. The actual reduction will be dependent on what is considered an acceptable threshold for each individual facility.

Other studies underway will investigate effective iron sulfate rates for acceptable dollar spot suppression and extended control with a standard chlorothalonil application. Our previous research has demonstrated a dollar spot reduction with 1 lb. iron sulfate/1,000 ft2. This suppression may be seen at lower rates, although our data is inconclusive at this point in our studies. Through June, we have been able to save one chlorothalonil application by incorporating iron sulfate.

As with any chemical or culturalmanagement strategy, the use of iron sulfate will most likely not eliminate dollar spot. This tactic should be used as part of an integrated approach to maintain turf below an unacceptable limit. Each of these studies will be repeated in 2017 on creeping bentgrass putting greens and fairways. c

Chlorothalonil Rate 0 fl. oz./1,000 ft2

1 fl. oz./1,000 ft2

2 fl. oz./1,000 ft2

Untreated Control

Ferrous Sulfate 1 lb./1.000 ft2

20 | Virginia Turfgrass Journal May/June 2016 www.vaturf.org

3 fl. oz./1,000 ft2

4 fl. oz./1,000 ft2

Research Report

Spring Dead Spot Control Using Fungicides

different fungicides and rates applied in the trial.

Research results

Virginia Tech Researchers: Cam Shelton, Graduate Research Assistant, and David McCall, Ph.D., Research Associate Research Sponsors: BASF, FMC, PBI-Gordon and Syngenta

S

pring dead spot (SDS) is one of the most common diseases of bermudagrass in the transition zone. The pathogen causing SDS attacks the stolons and rhizomes of the bermudagrass plant, leaving depressed voids of turf as the turf breaks dormancy in the spring.

To date, there is no silver bullet to consistently and completely control the disease in one growing season.

Turf managers normally utilize various management strategies to reduce this disease to acceptable levels, including the use of fungicides.

Product

Our research

Research trials were conducted at Tuscarora Country Club in Danville, VA, to determine fungicide efficacy against SDS. The research was conducted on a ‘MiniVerde’ ultradwarf bermudagrass practice putting green.

Fungicides were applied when soil temperature declined to approximately 65°F (September 18, 2015), followed by a second application four weeks later (October 16, 2015). Treatments were applied at a spray volume of 2 gal./1,000 ft2 and immediately watered in. Table 1 shows the Application A (9/18/2015)

Rate

Application B (10/16/2015)

Untreated check

March 10, 2016

Lexicon

0.47 fl. oz./ 1,000 ft2

Velista

0.7 oz./1,000 ft2

Headway

3 fl. oz./1,000 ft2

Velista Headway

0.7 oz./1,000 ft2 3 fl. oz./1,000 ft2

Briskway Headway

0.72 fl. oz./ 1.000 ft2 3 fl. oz./1,000 ft2

Kabuto

3.42 fl. oz./ 1,000 ft2

Kabuto

2 fl. oz./10,00 ft2

Kabuto

1.47 fl. oz./ 1,000 ft2

Frame + T

In this research study, Lexicon, Velista, Fame + T and Kabuto suppressed and reduced the severity of SDS compared to the untreated check.

Applications of Headway reduced the severity of SDS, but they did not reduce the diseased area or number of patches. Both rates tested of Kabuto showed the best control of SDS, but the disease is not currently on the label, and the product was applied above labeled rates for other diseases.

In the photo below, you can see control by Kabuto compared to the untreated check in the background.

This was the first year of testing Kabuto for the control of SDS, and it was applied at excessive rates. Future research will explore the consistency and efficacy of this product against SDS at more conventional rates. c

1 fl. oz./1,000

ft2

Table 1. Fungicides and rates used in this trial.

22 | Virginia Turfgrass Journal May/June 2016 www.vaturf.org

Untreated check

Kabuto 3.42 fl oz/ 1000 ft2 (1 app)

Research Summary

Organic Amendments Improve Tall Fescue Lawn Performance in Urban Soil Virginia Tech Researchers: Mike Badzmierowski, Ph.D. Student; Gregory Evanylo, Ph.D., Professor and Extension Specialist; and Erik Ervin, Ph.D., Professor of Turfgrass Culture & Physiology Research Sponsors: Metropolitan Washington Council of Governments and Virginia Agricultural Experiment Station

D

evelopment is a leading cause of urban soil degradation. The loss of organic matter and nutrient-rich topsoil and the subsequent compaction of subsoil typically result in a poor rooting medium for supporting plant growth.

Organic matter and nutrient-rich biosolids products may be used for renovating such disturbed soils by improving physical and chemical properties.

The objective of this study was to compare various biosolids-based organic amendments and inorganic fertilizer for establishment and production of turfgrass in disturbed urban soils. Exceptional-quality biosolids products, compared with soil test-recommended inorganic fertilizer rates, were: (1) dewatered anaerobically digested and pasteurized biosolids

from Alexandria, Virginia (Alexandria Renew Enterprises, ARE), (2) ARE biosolids blended with sand and sawdust at a ratio of 50% biosolids/25% sand/25% sawdust and (3) biosolids generated at three wastewater-treatment facilities in Spotsylvania County and composted with wood chips (Livingston Compost). All amendments were applied at a target rate of 200 lbs. N/acre.

Research plots were established in September 2013. Two irrigation rates, based on 0% and 80% evapotranspiration replacement, were applied.

Turfgrass color, quality and clipping yield were measured bi-weekly from establishment through the 2016 growing season.

During the initial season (September 2013 – August 2014),

24 | Virginia Turfgrass Journal May/June 2016 www.vaturf.org

fertilizer treatment outperformed the biosolids-based treatments for clipping yield and turf quality in both irrigated and non-irrigated plots. Fertilizer likely performed better than biosolids because nitrogen supplied by the split applications of fertilizer were more efficiently used than that supplied by the biosolids treatments, which were applied entirely prior to planting in September 2013.

During September 2014 – June 2015, all nutrient sources were split applied throughout the year. Biosolids products performed as well or better than the fertilizer during this period, likely due to residual effects of the organic products and greater N use efficiency due to split applications.

During July 2015 – May 2016, no amendments were applied to the trial area to test the effects of a “residual year.” Once again, biosolids products performed as well or better than the fertilizer during this period.

In June 2016, a Blue Plains dewatered and air-dried biosolids product to be marketed as “Bloom” was substituted for the ARE dewatered biosolids. A biosolids-sand-sawdust ratio of 1.5:1:1 was substituted for the ARE biosolids-sand-sawdust product.

Measurements of turfgrass color, quality and clipping yield will continue in addition to soil-atmosphere greenhouse-gas fluxes (i.e., CO2, CH4 and N2O) for the next several years. c

Research Summary

The Heating Characteristics of Tall Fescue/ Kentucky Bluegrass and Bermudagrass Sods Virginia Tech Researchers: Mike Goatley Jr., Ph.D., Professor and Extension Turfgrass Specialist; Whitnee Askew, Turfgrass Program Manager; and Jon Dickerson, Senior Research Specialist Research Cooperators: Jeff Everhart and Scott Woodward (Woodward Turf Farms, Remington, VA), the Virginia Turfgrass Foundation and the Virginia Agricultural Council

K

nowing more about the effects on sod-pallet heating — as influenced by turfgrass sod-harvest timing (morning vs. afternoon), turf cutting height and soil moisture at harvest — will allow producers to make informed decisions regarding the anticipated shelf life of cool-season turfgrass sods.

This study was conducted in May, August and October of 2015 on an 85/15 (% by weight at seed establishment) mixture of tall fescue [Festuca arundinacea L. (Schreb.)]/Kentucky bluegrass (Poa pratensis L.) sod at Woodward Turf Farm (Remington, VA) and on a tall fescue sod at the Virginia Tech Turfgrass Research Center (Blacksburg, VA).

The research utilized small-roll sizes (8.5 ft2) stacked on a pallet (540 ft2 total) at Remington or as individual rolls on a pallet at Blacksburg. For the sod farm site, remote temperature sensors set to record temperatures on 15-minute intervals for periods of at least 3 days were installed to record temperatures at specified lower, middle and upper locations of the sod on the pallet for sod harvested in either the afternoon or morning of the same or consecutive days (Photo 1).

At the Blacksburg site the pre-harvest treatments included varying mowing height (7.5 cm vs 5 cm) and dry (soil % volumetric water content targets of 15-20%) vs. moist (> than 25% VWC) at harvest. The sod was either immediately replaced in the field or hand-rolled with a sensor installed in the center of the roll and placed on a

pallet for 1, 8 or 24 hours when it was returned to the field and irrigated to monitor recovery. Time of harvest data varied for the three harvest months, with the afternoon harvest having the highest temperatures recorded for May and October.

As anticipated, heating was less in October than for other harvest months. While not part of the planned research, rain events on the

harvested sod on the pallet in the field impacted internal heating characteristics, seemingly trapping the accumulated heat load. While moist soil warmed more than dry when left on the pallet for 24 hours, moist soil at harvest was highly beneficial for sod recovery (Photo 2). There were no significant differences in heating or recovery characteristics based on variable cutting heights in these trials. c

Photo 1. Temperature sensors were installed near the bottom, middle and top layers of stacked sod in order to monitor sod-pallet heating characteristics over three or more days in the field at Woodward Turf Farms, Remington, VA.

Photo 2. Greater % volumetric soil water (VSW) contents at harvest provided much better recovery in the field trials at the Blacksburg Turfgrass Research Center.

26 | Virginia Turfgrass Journal May/June 2016 www.vaturf.org

Research Summary

Preemergence Crabgrass Control in Bermudagrass

it with Specticle for the second application since sprayable formulations of oxadiazon cannot be applied to actively growing bermudagrass.

Our research

Virginia Tech Researchers: Jeffrey Derr, Ph.D., Professor of Weed Science, and Adam Nichols, Research Assistant, Hampton Roads Ag. Research and Extension Center, Virginia Beach

T

his trial was initiated in an established stand of ‘Riviera’ bermudagrass. The purpose was to compare a split application to a single application of Dimension, Barricade, Pendulum and Specticle, common preemergence herbicides used for crabgrass control. The rate used for the single-application treatments was cut in half for each of the split-application treatments, so the total amount of herbicide was the same for a given product. We also evaluated Specticle at 2 applications of 9 fl. oz./A. Golf course superintendents and others maintaining bermudagrass are

Application A, 3/18/15 — 42°F air temperature; 47% relative humidity; 5% cloud cover; wind 9 MPH NNE. Rain 1 DAT.

concerned about needing to apply a crabgrass preventer prior to bermudagrass greenup. Therefore, they need to apply a crabgrass preventer before they know if winter injury or disease has thinned the turf stand. Most crabgrass preventers are root inhibitors, inhibiting the pegging down of bermudagrass runners. Ideally, it would be preferable to apply a crabgrass preventer that would not interfere with sprigging if the bermudagrass was injured during the winter.

Oxadiazon, commonly sold under the trade name Ronstar, is not a root inhibitor. We evaluated it as the early season treatment, following

Application B, 5/15/15 — 72°F air temperature; 62% relative humidity; 30% cloud cover; wind 8 MPH E. Irrigated 5 hours after treatment.

Research results

No bermudagrass injury was observed.

Split applications of Dimension and Pendulum AquaCap gave better crabgrass control than single applications, similar to what we have seen in the past. Single applications of Barricade and Specticle did better than split applications. Oxadiazon followed by Specticle was an effective treatment for crabgrass control. c

Percent Crabgrass Cover Treatment

June 17, 2015 91 DAT1 / 33 DAT2

Aug. 20, 2015 155 DAT1 / 97 DAT2

Sept. 24, 2015 190 DAT1 / 132 DAT2

53%

90%

97%

1

Untreated

2

Dimension

0.25 lb. ai/a AB

5%

18%

18%

3

Dimension

0.5 lb. ai/a A

4%

28%

28%

4

Barricade 4F

0.38 lb. ai/a AB

3%

9%

10%

5

Barricade 4F

0.75 lb. ai/a A

1%

1%

2%

6

Pendulum AquaCap

1.5 lb. ai/a AB

0%

1%

1%

7

Pendulum AquaCap

3.0 lb. ai/a A

2%

5%

7%

8

Specticle FLO

4.5 fl. oz./a AB

10%

33%

45%

9

Specticle FLO

9 fl. oz./a A

9%

15%

23%

10

Specticle

9 fl. oz./a AB

4%

3%

4%

11

Oxadiazon FLO

3.0 lb. ai/a A

1%

2%

3%

12

Oxadiazon FLO Specticle FLO

2.0lb. ai/a A 6 fl. oz./a B

1%

1%

2%

9

6

5

LSD P = .05 Table 1. Percent crabgrass cover over time.

Journal of the Virginia Turfgrass Council

| 27

Research Summary

Preemergence Crabgrass Control in Tall Fescue Virginia Tech Researchers: Jeffrey Derr, Ph.D., Professor of Weed Science, and Adam Nichols, Research Assistant, Hampton Roads Ag. Research and Extension Center, Virginia Beach

temperature; 47% relative humidity; 5% cloud cover; wind 9 MPH NNE. Rain 1 DAT. Application B, 5/15/15 — 72°F air temperature; 62% relative humidity; 30% cloud cover; wind 8 MPH E. Irrigated 5 hours after treatment.

Research results a given product. We included Specticle FLO in the study as it had been suggested that tall fescue could tolerate this herbicide. We applied Tenacity either once or twice to see if applications at 8 fluid ounces per acre (0.25 pounds active ingredient/acre) could provide acceptable crabgrass control.

Our research Application A, 3/18/15 — 42°F air

Specticle injured and thinned tall fescue. At least in this study, tall fescue did not have acceptable tolerance to Specticle. Both single and split applications of Dimension, Barricade and Pendulum and the single application of Specticle gave good to excellent crabgrass control. The split application of Specticle and both treatments of Tenacity gave lower crabgrass control than the other treatments. Tenacity does not have the length of control as the other products tested. c

6 7 8 9

Specticle FLO 9 fl. oz./a A

10

Tenacity

11

Tenacity LSD P = .05

0.25 lb. ai/a AB 0.25 lb. ai/a A

Sept. 24, 2015 190 DAT1 / 132 DAT2

Treatment

68%

1

0%

5%

3%

2

0%

4%

5%

3

0%

5%

8%

4

1%

5%

4%

5

0%

1%

2%

6

0%

5%

4%

7

1%

19%

16%

8

3%

6%

3%

9

Untreated 0.25 lb.

Dimension ai/a AB 0.5 lb.

Dimension ai/a A 0.38 lb.

Barricade 4F ai/a AB Barricade 4F 0.75 lb. ai/a A Pendulum AquaCap 1.5 lb. ai/a AB Pendulum 3.0 lb.

AquaCap ai/a A 4.5 fl. oz./a Specticle FLO AB Specticle FLO 9 fl. oz./a A

0%

15%

19%

10

Tenacity

1%

23%

29%

11

Tenacity

2

5

5

Table 1. Percent southern crabgrass cover over time.

LSD P = .05

0.25 lb. ai/a AB 0.25 lb. ai/a A

Sept. 24, 2015 Density 1 to 9 190 DAT / 132 DAT2

5

46%

Aug. 20, 2015 Density 1 to 9 155 DAT1 / 97 DAT2

4

1%

June 17, 2015 Density 1 to 9 91 DAT1 / 33 DAT2

3

0.25 lb.

Dimension ai/a AB 0.5 lb.

Dimension ai/a A 0.38 lb.

Barricade 4F ai/a AB Barricade 4F 0.75 lb. ai/a A Pendulum AquaCap 1.5 lb. ai/a AB Pendulum 3.0 lb.

AquaCap ai/a A 4.5 fl. oz./a Specticle FLO AB

April 10, 2015 Injury 1 to 9 23 DAT1 / 23 DAT2

2

Untreated

Aug. 20, 2015 155 DAT1 / 97 DAT2

1

Tall fescue

June 17, 2015 91 DAT1 / 33 DAT2

Treatment

Percent Crabgrass Cover

1

6

4

3

1

6

6

7

1

7

5

6

2

7

6

7

1

6

6

6

1

7

6

7

1

5

5

6

4

5

3

5

6

4

2

3

1

7

6

6

1

7

5

6

1

2

1

1

Table 2. Tall fescue injury and density in this study.

28 | Virginia Turfgrass Journal May/June 2016 www.vaturf.org

Tall fescue injury: 1 = no injury, 9 = complete death Tall fescue density: 1 = no stand, 9 = complete turf cover

T

his trial was initiated in an established stand of ‘Southern Belle’ tall fescue.

The purpose was to compare split applications to single applications of Dimension, Barricade and Pendulum, common preemergence herbicides used for crabgrass control. The rate used for the single-application treatments was cut in half for each of the split-application treatments, so the total amount of herbicide was the same for

Research Summary

New Hands-Off Approach for Monitoring Drought Stress to Creeping Bentgrass and Bermudagrass Virginia Tech Researchers: Travis Roberson, Graduate Research Assistant, and David McCall, Ph.D., Research Associate Research Sponsors: the Virginia Agricultural Council and the Virginia Turfgrass Foundation

W

ater conservation efforts continue to be a high priority for turf managers throughout the world. Most turfgrasses are often over-watered because of isolated underlying soils that tend to dry down faster than others. Many golf course superintendents and sports turf managers have transitioned to routinely monitoring of site-specific needs with the aid of handheld soil moisture meters for localized hand watering. This method can save tremendous amounts of water, but it can be time consuming and may lead to missed areas in need of irrigation.

Measuring light reflectance from the turf canopies is a rapid means for

collecting large amounts of data and is being explored by several researchers, including our lab at Virginia Tech.

The normalized difference vegetation index (NDVI) is most commonly used for rapid reflectance measurement because of an increased sensitivity to stress from near infrared light. This index can be related to visual turf quality, nitrogen needs, water needs and disease outbreaks.

The primary issue is the inability to differentiate insufficient moisture from other stressors. We have explored the use of a water band index (WBI) that quantifies water-absorption features of creeping bentgrass canopies in sandy soils, and we found this to be more closely related to water stress

than NDVI and is independent of nutritional needs.

The next question that our lab aims to address is how the WBI translates to creeping bentgrass and hybrid bermudagrass grown in various soil textures.

We are currently testing this method with each grass species on straight sand, organic-amended sand, sandy loam, silt loam and clay soils. Once relationships are established, we will continue exploring the WBI and related vegetation indices derived from light reflectance on a larger scale using unmanned aerial systems (drones). Our ultimate goal is for rapid, early detection of drought stress across multiple soil textures found within property with the use of drones. c

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Journal of the Virginia Turfgrass Council

| 29

Turfgrass Calendar September 12

October 20–21

January 24–27, 2017

February 4–9, 2017

Bob Ruff Jr. Memorial Research Golf Tournament

GIE+EXPO and Hardscape North America

STMA Conference and Exhibition

Golf Industry Show

December 5–8

January 30 – February 2, 2017

Wintergreen Resort — Devil’s Knob Wintergreen, VA

October 19–21 Landscapes 2016

(formerly the PLANET Green Industry Conference) Louisville, KY

Kentucky Expo Center Louisville, KY

Short Course

Belmont Golf Course Henrico County, VA

Orlando, FL

Mid-Atlantic Turfgrass Expo

Fredericksburg Expo & Conference Center Fredericksburg, VA

Orange County Convention Center Orlando, FL

February 28 – March 1, 2017 Come to the Bay

Virginia Beach Resort Hotel Virginia Beach, VA

Digital Marketplace Scan the QR code: Download your favorite QR reader to your phone and scan the code to learn more about these companies.

30 | Virginia Turfgrass Journal May/June 2016 www.vaturf.org