MARK M. MAHADY & ASSOCIATES, INC. Consultant To The Turfgrass Industry

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1 MARK M. MAHADY & ASSOCIATES, INC. Consultant To The Turfgrass Industry An Evaluation of Trimmit SC for Suppression and Control of Annual Bluegrass in Creeping Bentgrass Putting Greens Located in California Coastal and Inland Locations Mark Mahady, Mark M. Mahady and Associates, Inc. Dean Mosdell, Ph.D., Syngenta Crop Protection, Inc. Mike McCullough, Northern California Golf Course Association Todd Cook and Lonnie Stevens, Poppy Ridge Golf Course Rick Key, Salinas Fairways Golf Course August 5, 00 Prepared By Mark M. Mahady, M.S. Certified Professional Agronomist President, Mark M. Mahady & Associates, Inc. 51 Country Club Drive, Carmel Valley, CA 99 Phone/Fax (81) :

2 Mark M. Mahady & Associates, Inc. Trimmit SC for Control of Annual Bluegrass in Creeping Bentgrass Putting Greens Introduction Many golf course superintendents located in the Northwest and the Midwest presently utilize a multiple application program of Trimmit SC (paclobutrazol) for successful suppression and control of annual bluegrass or Poa (Poa annua) in creeping bentgrass putting greens. The program concept uses a spring and fall application format at rates ranging from 8 to 16 ounces of Trimmit per acre with approximately three treatments in each season applied at four-week intervals. Field and research observations indicate that Poa annua is highly susceptible to the growth regulation properties of Trimmit. Repeat applications tend to reduce the size of individual Poa plants, actually making the plants more compact and diminutive (Photograph 1). The result is a Poa plant that is much less competitive and much less likely to spread and proliferate, particularly in a mixed stand with creeping bentgrass. As the Poa is regulated, the stolons from creeping bentgrass slowly advance, actually growing over the smaller Poa plants, and eventually occupying the space once held by the invading Poa. Photograph 1. Trimmit regulates Poa annua growth and makes Poa annua plants more diminutive and less competitive in stands of creeping bentgrass Mark M. Mahady & Associates, Inc. Seasonal weather conditions are another important variable that influence the competitive balance between bentgrass and Poa populations. The summer season in the Northwest and Midwest often presents a multitude of conditions that may include extremes in heat, humidity and disease stress.

3 Mark M. Mahady & Associates, Inc. Trimmit SC for Control of Annual Bluegrass in Creeping Bentgrass Putting Greens These types of climatic extremes favor the growth of bentgrass over Poa because bentgrass has a wider range of tolerance to these adverse conditions. Many believe that combining summer stress conditions with a Trimmit program would actually improve the potential for suppression and control of Poa annua. Poa subject to summer stress would exhibit poor vigor and when combined with the growth regulation effects of Trimmit would be more susceptible to decline. Under such conditions creeping bentgrass would have a dynamic competitive advantage over Poa annua. With these thoughts in mind, the question arises, How would the Trimmit program for suppression/control of Poa annua in creeping bentgrass putting greens perform in the diverse microclimates of California? California presents a multitude of microclimates. Coastal climates in Northern California are truly moderate. Early morning fog is common during the summer and often may not burn off until mid-day. As an example, the average maximum temperatures in Salinas, California during the months from May to September ranges from 67.5 to 7.5 F. In contrast, more inland climates such as Livermore, California are considerably warmer than coastal climates during the summer months. Early morning fog is much less common and if present burns off early after sunrise. The average maximum temperature in Livermore, California during the months from May to September, ranges from 77.0 to 89.8 F. During the month of July the average maximum temperature in the inland microclimate of Livermore is 18.7 degrees hotter (Table 1) than the coastal climate of Salinas. Table 1. A comparison of average monthly maximum temperature in Salinas, California (coastal) and Livermore, California (inland) over a 0-year period from 1961 to Derived from NCDC TD 961 Clim Normals. Sal F Ave. Max Liv F Ave Max Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year F In an attempt to address the impact of microclimate on the performance of Trimmit, two similar research protocols were deployed on creeping bentgrass putting greens located in two very different microclimates. One trial was located in the coastal climate of Salinas, California. The second trial was located in the inland climate of Livermore, California. The objectives of these Trimmit field studies were to determine the following: 1. Will multiple spring and fall treatments of Trimmit SC exhibit acceptable suppression/control of Poa annua in creeping bentgrass putting greens?. Will the level of Poa annua suppression and control be similar in each microclimate?. Is such a program safe for use on a high quality bentgrass putting surface?. Is Trimmit SC a practical tool for golf course superintendents to consider within the scope of an effective Poa annua management program?

4 Mark M. Mahady & Associates, Inc. Trimmit SC for Control of Annual Bluegrass in Creeping Bentgrass Putting Greens Materials & Methods Similar Trimmit protocols were deployed at Salinas Fairways Golf Course (SFGC) located in Salinas, California, representing a coastal microclimate, and Poppy Ridge Golf Course (PRGC) located near Livermore, California, representing an inland microclimate. The SFGC field study was conducted on the practice putting green. This Dominant creeping bentgrass putting green exhibited an average of.% Poa cover on the day of the first Trimmit application on March 0, 00. The practice putting green is six years old and is mowed seven days per week at a cutting height of 15/1000ths. The PRGC field study was also conducted on the practice putting green. This Dominant creeping bentgrass putting green exhibited an average of 1.8% Poa cover on the day of the first Trimmit application on April 1, 00. The practice putting green is five years old and is mowed seven days per week at a cutting height of 10/1000ths. Photographs &. The two Trimmit field research trials were located at Poppy Ridge Golf Course (left) and Salinas Fairways Golf Course (right) Mark M. Mahady & Associates, Inc. As previously mentioned, these two microclimates are quite different. This Salinas location is classified as a coastal Mediterranean climate with cool, foggy summer conditions. The average maximum temperatures in Salinas, California from May to September range from 67.5 to 7.5 F with occasional temperature spikes into the 90 s. Nighttime minimum temperatures during this period range from 9.1 to 5.5 F. Winters are moderate with average maximum air temperatures ranging from 60.8 F to 6.1 F and nighttime low temperatures of 5. F to 0.5 F. Average yearly rainfall is 1. inches with a very high percentage of precipitation occurring during the winter months from November to March. This Livermore location is classified as an inland climate with warm summer conditions and crisp winter temperatures. The average maximum temperatures in Livermore, California from May to September, ranges from 77.0 to 89.8 F. with occasional temperature spikes into the 100 s. Nighttime minimum temperatures during this period range from 6.8 to 5. F. Winters are moderate with average maximum air temperatures ranging from 56.5 F to 6.8 F and nighttime low temperatures of 5. F to. F. Average yearly rainfall is 1.6 inches with a very high percentage of precipitation occurring during the winter months from November to March.

5 Mark M. Mahady & Associates, Inc. Trimmit SC for Control of Annual Bluegrass in Creeping Bentgrass Putting Greens 5 Eight Trimmit SC applications were deployed at the rates presented in Table to a stand of Dominant creeping bentgrass at SFGC with.% Poa annua invasion beginning on March 0, 00. Treatments were deployed on March 0, April 6, May, June, July 0, September 9, October 8, and November, 00. Table. Trimmit SC application schedule at Salinas Fairways Golf Course, Salinas, CA. Rick Key, Superintendent. 00. Mark M. Mahady & Associates, Inc. Application Treatments Rate Schedule 1 1 Check * * Trimmit SC.0 oz/a /0, /6, 5/, 6/, 7/0, 9/9, 10/8, 11//0 Trimmit SC 8.0 oz/a /0, /6, 5/, 6/, 7/0, 9/9, 10/8, 11//0 Trimmit SC 1.0 oz/a /0, /6, 5/, 6/, 7/0, 9/9, 10/8, 11//0 5 Trimmit SC 16.0 oz/a /0, /6, 5/, 6/, 7/0, 9/9, 10/8, 11//0 6 Trimmit SC + Primo Maxx 6.0 oz/a oz/a /0, /6, 5/, 6/, 7/0, 9/9, 10/8, 11//0 7 Prograss 1.5 EC 8. oz/a /0, /6, 5/, 6/, 7/0, 9/9, 10/8, 11//0 1 Eight Trimmit SC applications. A similar Trimmit SC treatment protocol consisting of seven Trimmit applications as presented in Table was deployed at PRGC to a stand of Dominant creeping bentgrass with 1.8% Poa annua invasion beginning on April 1, 00. Treatments were deployed on April 1, April 8, May 8, September 11, October 9, November, and December 1, 00. The Prograss treatment received only six applications. Table Trimmit SC application schedule at Poppy Ridge Golf Course. Livermore, CA. Todd Cook, Superintendent Mark M. Mahady & Associates, Inc. Application Treatments Rate Schedule 1 1 Check * * Trimmit SC.0 oz/a /1, /8, 5/8, 9/11, 10/9, 11/, 1/1/0 Trimmit SC 8.0 oz/a /1, /8, 5/8, 9/11, 10/9, 11/, 1/1/0 Trimmit SC 1.0 oz/a /1, /8, 5/8, 9/11, 10/9, 11/, 1/1/0 5 Trimmit SC 16.0 oz/a /1, /8, 5/8, 9/11, 10/9, 11/, 1/1/0 6 Trimmit SC + Primo Maxx 6.0 oz/a oz/a /1, /8, 5/8, 9/11, 10/9, 11/, 1/1/0 7 Prograss 1.5 EC 8. oz/a /1, /8, 5/8, 9/11, 10/9, 11//0 1 Seven Trimmit SC applications. Individual treatment plots at both locations measured 5 x 10 with aisle ways. Treatments were replicated four times in a randomized complete block design. A calibrated CO propelled spray system pressurized to 8 psi and equipped with 1100LP Tee-Jet nozzles applied treatments at a spray volume of 65 gallons per acre. A pacing watch was used for all spray applications to ensure the uniform and accurate delivery of all treatments.

6 Mark M. Mahady & Associates, Inc. Trimmit SC for Control of Annual Bluegrass in Creeping Bentgrass Putting Greens 6 At the SFGC location treatment evaluations were conducted on March 0, April 6, May, June, July 0, September 9, October 8, November and December 11, 00. At the PHGC location treatments were evaluated on April 1, April 8, May 8, September 11, October 9, November, December 1, 00, and January, 00. Turf color was rated utilizing a 0-10 scale with 0 representing no green color, 6 minimally acceptable green color and 10 very dark green color. Turf quality was rated on a 0-10 scale with 0 representing no live turf and the poorest surface quality possible, 6 minimally acceptable putting green quality and 10 perfect putting green conditions. Turf injury was rated on a 0-10 scale with 0 representing no injury, the maximum level of acceptable injury and 10 dead turf. Percent annual bluegrass cover was estimated with visual evaluations. Percent annual bluegrass control was statistically calculated against the percent Poa annua cover in the untreated check plot. Data were summarized and statistically analyzed. Differences between means were determined via LSD. Results and Discussion The Influence of Trimmit on Creeping Bentgrass Color (Tables and A) At SFGC (Table ) multiple tank mixed treatments of Trimmit at 8 ounces of product per acre (oz/a) plus Primo Maxx at 5.5 oz/a resulted in the most consistent, statistically significant improvement in creeping bentgrass color when compared to the untreated check over the course of the nine month trial. Statistically significant results are presented in red highlights in all tables. Creeping bentgrass showed statistically significant improvement in color versus the untreated check with the Trimmit/Primo tank mix on six of nine rating dates. Trimmit alone at 1 0z/A and 16 oz/a showed statistically significant improvement in color versus the untreated check on four of nine rating dates. Trimmit is known to enhance the color of grasses such as creeping bentgrass and perennial ryegrass. If treatment evaluations had been conducted more frequently, such as every week or every two weeks instead of every four weeks, Trimmit may have shown potential to enhance bentgrass at rates as low as and 8 oz/a. Table. The Influence of Trimmit SC on Bentgrass Color. Salinas Fairways Golf Course, Salinas, CA. Rick Key, Superintendent. 00. Mark M. Mahady & Associates, Inc. Bent Bent Bent Bent Bent Bent Bent Bent Bent Color 1 Color Color Color Color Color Color Color Color /0 /6 5/ 6/6 7/0 9/9 10/8 11/ 1/11/0 Treatments Rate DOA1 DOA DOA DOA DOA5 DOA6 DOA7 DOA8 7DAT8 1 Check * 6.0 a 6.88 b 7.00 b 7.00 b 6.5 b 7.0 a 7.00 a 6.00 a 6.00 e Trimmit SC.0 oz/a 6.0 a 7.00 b 7.00 b 7.00 b 6.75 ab 7.0 a 7.00 a 6.00 a 6.75 d Trimmit SC 8.0 oz/a 6.0 a 7.5 b 7.00 b 7.00 b 7.00 ab 7.0 a 7.5 a 5.50 ab 7.00 cd Trimmit SC 1.0 oz/a 6.0 a 7.88 a 7.00 b 7.1 b 7.5 a 7.0 a 7.50 a.75 c 7.5 bc 5 Trimmit SC 16.0 oz/a 6.0 a 7.88 a 7.00 b 7.1 b 7.8 a 7.0 a 7.6 a.88 c 7.8 b 6 Trimmit + Primo oz/a 6.0 a 8.1 a 7.75 a 7.50 a 7.6 a 7.0 a 7.50 a 5.1 bc 8.00 a 7 Prograss 1.5 EC 8. oz/a 6.0 a 7.00 b 7.00 b 7.00 b 6.75 ab 7.0 a 7.00 a 6.00 a 6.1 e LSD (P=.05) Bentgrass color was rated on a 0-10 scale with 0 representing no green color, 6 minimally acceptable green color and 10 very dark green color. Days after treatment eight.

7 Mark M. Mahady & Associates, Inc. Trimmit SC for Control of Annual Bluegrass in Creeping Bentgrass Putting Greens 7 At PRGC (Table A) Trimmit did not exhibit the same degree nor frequency of bentgrass color enhancement as was observed at SFGC. Creeping bentgrass showed statistically significant improvement in color versus the untreated check with the Trimmit/Primo tank mix on two of ten rating dates. Trimmit alone at 1 oz/a and 16 oz/a showed statistically significant improvement in color versus the untreated check on one of ten rating dates. Table A. The Influence of Trimmit SC on Bentgrass Color. Poppy Ridge Golf Course, Livermore, CA. Todd Cook, Superintendent Mark M. Mahady & Associates, Inc. Bent Bent Bent Bent Bent Bent Bent Bent Bent Bent Color 1 Color Color Color Color Color Color Color Color Color /1 /8 5/8 6/8 8/1 9/11 10/9 11/5 1/1/0 1//0 Treatments Rate DOA1 DOA DOA 1DAT 78DAT DOA DOA5 DOA6 DOA7 DAT7 1 Check * 7.0 a 7.00 a b 7.00 b 6.75 ab 6.0 a 6.00 ab 5.75 a 7.00 a 6.0 a Trimmit SC.0 oz/a 7.0 a 7.00 a b 7.00 b 6.8 b 6.0 a 6.00 ab 6.5 a 7.8 a 6.0 a Trimmit SC 8.0 oz/a 7.0 a 6.88 ab b 7.00 b 6.6 ab 6.0 a 6.00 ab 5.6 a 7.00 a 6.0 a Trimmit SC 1.0 oz/a 7.0 a 6.50 b 6.65 b 7.00 b 6.75 ab 6.0 a 6.00 ab 5.50 a 7.50 a 6.0 a 5 Trimmit SC 16.0 oz/a 7.0 a 5.88 c 6.56 b 7.00 b 6.75 ab 6.0 a 6.50 a 5.6 a 6.88 a 6.0 a 6 Trimmit + Primo oz/a 7.0 a 7.1 a 7.65 a 7.6 a 6.88 a 6.0 a 6.5 ab 5.88 a 7.50 a 6.0 a 7 Prograss 1.5 EC 8. oz/a 7.0 a 6.88 ab b 6.88 b 6.88 a 6.0 a 5.75 b 5.75 a 6.75 a 6.0 a LSD (P=.05) Bentgrass color was rated on a 0-10 scale with 0 representing no green color, 6 minimally acceptable green color and 10 very dark green color. Days after treatment seven. The Influence of Trimmit on Creeping Bentgrass Injury (Tables 5 and 5A) Within the scope of these four-week evaluation formats, Trimmit exhibited very few statistically significant injury rating events. At SFGC (Table 5) multiple applications of Trimmit at 1 and 16 oz/a resulted in statistically significant injury to creeping bentgrass when compared to the untreated check on only one of nine rating dates. These injury levels were not severe and fell within a range of what would be perceived to be acceptable from a golf course superintendents perspective. Similar trends were observed at PRGC (Table 5A). Trimmit at 16 oz/a resulted in statistically significant injury to creeping bentgrass when compared to the untreated check on only one of nine rating dates. The protocol format for this field trial designated treatment evaluations approximately every four weeks. At a four-week rating interval few injury issues were observed with Trimmit even at the highest application rate of 16 oz/a. No injury ratings were conducted 1, or weeks after application. No reports from the on-site superintendents were received concerning unacceptable levels of injury one to three weeks following Trimmit applications. Prograss exhibited the most severe injury to creeping bentgrass of all treatments reviewed at PRGC. Prograss exhibited a consistent trend for bentgrass injury in two of four replications at PRGC. Multiple applications of Prograss at 8. oz/a (0. gallons/a) resulted in statistically significant injury to creeping bentgrass when compared to the untreated check on two of nine rating dates. However, Prograss exhibited unacceptable levels of injury to creeping bentgrass during all three rating dates following the fifth Prograss application. At PRGC in plot areas with consistent traffic and slightly moist conditions, Trimmit caused very slight thinning of creeping bentgrass for a short time at the 1 and 16 oz/a rates. In those areas with normal moisture levels no thinning or reduction in surface quality was noted. Under higher spring temperatures the 16 oz Trimmit rate caused slight discoloration of creeping bentgrass.

8 Mark M. Mahady & Associates, Inc. Trimmit SC for Control of Annual Bluegrass in Creeping Bentgrass Putting Greens 8 Avoid applying Trimmit approximately weeks prior to or after weeks hollow tine aerification and sand topdressing. Trimmit reduces vertical leaf extension of creeping bentgrass. If Trimmit is applied too soon before or after aeration and sand topdressing, it will reduce the vertical growth of bentgrass and slow the movement of grass blades through the sand topdressing layer. Table 5. The Influence of Trimmit SC on Bentgrass Injury. Salinas Fairways Golf Course, Salinas, CA. Rick Key, Superintendent. 00. Mark M. Mahady & Associates, Inc. Bent Bent Bent Bent Bent Bent Bent Bent Bent Injury 1 Injury Injury Injury Injury Injury Injury Injury Injury /0 /6 5/ 6/6 7/0 9/9 10/8 11/ 1/11/0 Treatments Rate DOA1 DOA DOA DOA DOA5 DOA6 DOA7 DOA8 7DAT8 1 Check * 0.0 a 0.00 a 0.0 a 0.0 a 0.00 a 0.0 a 0.0 a 0.00 c 0.0 a Trimmit SC.0 oz/a 0.0 a 0.00 a 0.0 a 0.0 a 0.00 a 0.0 a 0.0 a 0.00 c 0.0 a Trimmit SC 8.0 oz/a 0.0 a 0.5 a 0.0 a 0.0 a 0.00 a 0.0 a 0.0 a 0.75 bc 0.0 a Trimmit SC 1.0 oz/a 0.0 a 0.1 a 0.0 a 0.0 a 0.00 a 0.0 a 0.0 a 1.8 ab 0.0 a 5 Trimmit SC 16.0 oz/a 0.0 a 0.8 a 0.0 a 0.0 a 0.00 a 0.0 a 0.0 a 1.88 a 0.0 a 6 Trimmit + Primo oz/a 0.0 a 0.00 a 0.0 a 0.0 a 0.00 a 0.0 a 0.0 a 0.75 bc 0.0 a 7 Prograss 1.5 EC 8. oz/a 0.0 a 0.00 a 0.0 a 0.0 a 0.8 a 0.0 a 0.0 a 0.50 bc 0.0 a LSD (P=.05) Bentgrass injury was rated on a 0-10 scale with 0 representing no injury, a maximum level of allowable injury and 10 dead turf. Days after treatment eight. Photograph. Injury to creeping bentgrass following five Prograss treatments applied at a rate of 8. oz/a or 0. gal/a. Note severe bentgrass thinning. Poppy Ridge Golf Course Mark M. Mahady & Associates, Inc.

9 Mark M. Mahady & Associates, Inc. Trimmit SC for Control of Annual Bluegrass in Creeping Bentgrass Putting Greens 9 Table 5A. The Influence of Trimmit SC on Bentgrass Injury. Poppy Ridge Golf Course, Livermore, CA. Todd Cook, Superintendent Mark M. Mahady & Associates, Inc. Bent Bent Bent Bent Bent Bent Bent Bent Bent Bent Injury 1 Injury Injury Injury Injury Injury Injury Injury Injury Injury /1 /8 5/8 6/8 8/1 9/11 10/9 11/5 1/1/0 1//0 Treatments Rate DOA1 DOA DOA 1DAT 78DAT DOA DOA5 DOA6 DOA7 DAT7 1 Check * 0.0 a b b 0.00 a 0.00 a 0.00 a 0.00 a 0.00 b 0.00 a 0.00 a Trimmit SC.0 oz/a 0.0 a b b 0.00 a 0.00 a 0.00 a 0.00 a 0.00 b 0.00 a 0.00 a Trimmit SC 8.0 oz/a 0.0 a b 0.06 b 0.00 a 0.00 a 0.00 a 0.00 a 0.00 b 0.00 a 0.50 a Trimmit SC 1.0 oz/a 0.0 a b 0.50 b 0.1 a 0.00 a 0.00 a 0.00 a 0.50 b 0.6 a 0.88 a 5 Trimmit SC 16.0 oz/a 0.0 a a 0.65 b 0.1 a 0.00 a 0.00 a 0.00 a 0.50 b 0.50 a 1.00 a 6 Trimmit + Primo oz/a 0.0 a 0.50 b 0.06 b 0.00 a 0.00 a 0.00 a 0.00 a 0.00 b 0.00 a 0.50 a 7 Prograss 1.5 EC 8. oz/a 0.0 a 0.15 b a 0.6 a 0.00 a 0.00 a.6 a.6 a.75 a.50 a LSD (P=.05) Bentgrass injury was rated on a 0-10 scale with 0 representing no injury, a maximum level of allowable injury and 10 dead turf. Days after treatment seven. The Influence of Trimmit on Creeping Bentgrass Quality (Tables 6 and 6A) Overall, few treatments exhibited dynamic enhancement in creeping bentgrass quality when compared to the untreated check over the course of the nine-month field trial. At SFGC (Table 6) multiple tank mixed treatments of Trimmit at 8 oz/a plus Primo Maxx at 5.5 oz/a resulted in a statistically significant improvement in creeping bentgrass quality on two of nine rating dates. Multiple treatments of Trimmit alone at 16 oz/a resulted in a statistically significant improvement in creeping bentgrass quality on only one of nine rating dates. Table 6. The Influence of Trimmit SC on Bentgrass Quality. Salinas Fairways Golf Course, Salinas, CA. Rick Key, Superintendent. 00. Mark M. Mahady & Associates, Inc. Bent Bent Bent Bent Bent Bent Bent Bent Bent Quality 1 Quality Quality Quality Quality Quality Quality Quality Quality /0 /6 5/ 6/6 7/0 9/9 10/8 11/ 1/11/0 Treatments Rate DOA1 DOA DOA DOA DOA5 DOA6 DOA7 DOA8 7DAT8 1 Check * 7.0 a 7.88 a 8.00 b 8.00 a 7.00 b 8.0 a 8.00 a 7.00 a 7.8 a Trimmit SC.0 oz/a 7.0 a 8.00 a 7.88 b 7.88 a 7.00 b 8.0 a 8.00 a 7.00 a 8.0 a Trimmit SC 8.0 oz/a 7.0 a 7.6 a 8.00 b 7.75 a 7.1 b 8.0 a 8.00 a 6.75 ab 8.0 a Trimmit SC 1.0 oz/a 7.0 a 7.88 a 8.00 b 8.00 a 7.8 ab 8.0 a 8.00 a 6.50 ab 8.0 a 5 Trimmit SC 16.0 oz/a 7.0 a 7.75 a 8.00 b 8.00 a 7.8 ab 8.0 a 7.75 a 6.5 b 7.8 a 6 Trimmit + Primo oz/a 7.0 a 8.5 a 8.8 a 8.1 a 7.75 a 8.0 a 8.5 a 6.6 ab 8.0 a 7 Prograss 1.5 EC 8. oz/a 7.0 a 8.1 a 8.00 b 8.00 a 7.1 b 8.0 a 8.00 a 7.00 a 8.0 a LSD (P=.05) Bentgrass quality was rated on a 0-10 scale with 0 representing no quality, 6 minimally acceptable quality and 10 the very best quality. Days after treatment eight.

10 Mark M. Mahady & Associates, Inc. Trimmit SC for Control of Annual Bluegrass in Creeping Bentgrass Putting Greens 10 At PRGC (Table 6A) multiple treatments of Trimmit alone at 16 oz/a resulted in a statistically significant improvement in creeping bentgrass quality on only one of ten rating dates. Table 6A. The Influence of Trimmit SC on Bentgrass Quality. Poppy Ridge Golf Course, Livermore, CA. Todd Cook, Superintendent Mark M. Mahady & Associates, Inc. Bent Bent Bent Bent Bent Bent Bent Bent Bent Bent Quality 1 Quality Quality Quality Quality Quality Quality Quality Quality Quality /1 /8 5/8 6/8 8/1 9/11 10/9 11/5 1/1/0 1//0 Treatments Rate DOA1 DOA DOA 1DAT 78DAT DOA DOA5 DOA6 DOA7 DAT7 1 Check * 9.0 a 7.88 a 8.00 a 8.1 a 8.1 a 8.0 a 8.00 a 8.00 a 8.00 a 7.50 a Trimmit SC.0 oz/a 9.0 a 8.00 a 8.00 a 8.00 a a 8.0 a 8.00 a 8.00 a 8.00 a 7.6 a Trimmit SC 8.0 oz/a 9.0 a 8.00 a 7.88 a 8.00 a 8.15 a 8.0 a 8.00 a 8.00 a 8.00 a 8.0 a Trimmit SC 1.0 oz/a 9.0 a 7.6 a 7.6 a 7.88 a 8.50 a 8.0 a 8.00 a 7.6 a 7.6 a 8.00 a 5 Trimmit SC 16.0 oz/a 9.0 a 7.00 b 6.75 a 7.88 a 8.75 a 8.0 a 8.00 a 7.75 a 8.00 a 8.8 a 6 Trimmit + Primo oz/a 9.0 a 7.6 a 7.88 a 8.00 a 8.1 a 8.0 a 8.00 a 8.00 a 7.88 a 8.8 a 7 Prograss 1.5 EC 8. oz/a 9.0 a 7.88 a 7.00 a 7.50 a a 8.0 a 6.1 a 5.50 a 5.8 a 5.75 a LSD (P=.05) Bentgrass quality was rated on a 0-10 scale with 0 representing no quality, 6 minimally acceptable quality and 10 the very best quality. Days after treatment seven. The Influence of Trimmit on Poa annua Injury (Tables 7 and 7A) At SFGC (Table 7) multiple Trimmit treatments resulted in only minor and subtle injury and plant growth regulator symptoms to Poa annua throughout the course of the nine-month field trial. Trimmit at 1 oz/a resulted in statistically significant injury to Poa annua on two of nine rating dates. Trimmit at 16 oz/a resulted in statistically significant injury to Poa annua on only one of nine rating dates. Multiple tank mixed treatments of Trimmit at 8 oz/a plus Primo Maxx at 5.5 oz/a resulted in a statistically significant injury to Poa annua on only one of nine rating dates. It is hypothesized that the very cool and moderate temperatures of this coastal climate, combined with moderate humidity and low stress potential for Poa annua, reduces the effectiveness of Trimmit in this microclimate. In contrast, multiple Trimmit applications resulted in much more noticeable injury and plant growth regulator effects on Poa annua at PRGC (Table 7A). Trimmit at 1 oz/a and 16 oz/a resulted in statistically significant injury to Poa annua on four of ten rating dates, respectively. Multiple tank mixed treatments of Trimmit at 8 oz/a plus Primo Maxx at 5.5 oz/a resulted in a statistically significant injury to Poa annua on three of ten rating dates. Six applications of Prograss at.8 oz/a or 0. gal/a resulted in a statistically significant injury to Poa annua on two of nine rating dates. It is hypothesized that the much hotter summer temperatures of the inland climate increased the total stress level on Poa annua. This effect combined with the plant growth regulator effects of Trimmit, enhanced injury to Poa annua.

11 Mark M. Mahady & Associates, Inc. Trimmit SC for Control of Annual Bluegrass in Creeping Bentgrass Putting Greens 11 Table 7. The Influence of Trimmit SC on Poa annua Injury. Salinas Fairways Golf Course, Salinas, CA. Rick Key, Superintendent. 00. Mark M. Mahady & Associates, Inc. Poa Poa Poa Poa Poa Poa Poa Poa Poa Injury 1 Injury Injury Injury Injury Injury Injury Injury Injury /0 /6 5/ 6/6 7/0 9/9 10/8 11/ 1/11/0 Treatments Rate DOA1 DOA DOA DOA DOA5 DOA6 DOA7 DOA8 7DAT8 1 Check * 0.0 a 0.00 a b 0.00 a 0.0 a 0.0 a 0.0 a 0.00 b 0.0 a Trimmit SC.0 oz/a 0.0 a 0.1 a 0.8 ab 0.00 a 0.0 a 0.0 a 0.0 a 0.00 b 0.0 a Trimmit SC 8.0 oz/a 0.0 a 0.5 a ab 0.88 a 0.0 a 0.0 a 0.0 a 0.75 ab 0.0 a Trimmit SC 1.0 oz/a 0.0 a 0.5 a a 0.00 a 0.0 a 0.0 a 0.0 a 1.75 a 0.0 a 5 Trimmit SC 16.0 oz/a 0.0 a 0.50 a 0.8 ab 0.1 a 0.0 a 0.0 a 0.0 a.5 a 0.0 a 6 Trimmit + Primo oz/a 0.0 a 0.1 a 0.15 b 0.00 a 0.0 a 0.0 a 0.0 a 1.6 a 0.0 a 7 Prograss 1.5 EC 8. oz/a 0.0 a 0.00 a b 0.00 a 0. a 0.0 a 0.0 a 1.5 ab 0.0 a LSD (P=.05) Poa annua injury was rated on a 0-10 scale with 0 representing no injury, a maximum level of allowable injury and 10 dead turf. Days after treatment eight. Table 7A. The Influence of Trimmit SC on Poa annua Injury. Poppy Ridge Golf Course, Livermore, CA. Todd Cook, Superintendent Mark M. Mahady & Associates, Inc. Poa Poa Poa Poa Poa Poa Poa Poa Poa Poa Injury 1 Injury Injury Injury Injury Injury Injury Injury Injury Injury /1 /8 5/8 6/8 8/1 9/11 10/9 11/5 1/1/0 1//0 Treatments Rate DOA1 DOA DOA 1DAT 78DAT DOA DOA5 DOA6 DOA7 DAT7 1 Check * 0.0 a 1.50 a c c 0.0 a 0.0 a 0.5 a 0.0 b 0.0 c 0.0 a Trimmit SC.0 oz/a 0.0 a a 0.75 bc 1.15 bc 0.0 a 0.0 a 0.50 a 0.0 b 0.0 c 0.0 a Trimmit SC 8.0 oz/a 0.0 a 1.81 a 0.81 abc bc 0.0 a 0.0 a 0.50 a 0.0 b 1. bc 0.0 a Trimmit SC 1.0 oz/a 0.0 a.50 a 1.50 ab.15 a 0.0 a 0.0 a 1.8 a 1.5 a.5 b 0.0 a 5 Trimmit SC 16.0 oz/a 0.0 a a a.81 a 0.0 a 0.0 a 1.8 a 1. a.8 a 0.0 a 6 Trimmit + Primo oz/a 0.0 a.000 a ab.000 b 0.0 a 0.0 a 0.6 a 0.5 ab.5 b 0.0 a 7 Prograss 1.5 EC 8. oz/a 0.0 a 1.65 a 0.75 bc c 0.0 a 0.0 a 1.5 a 1. a.5 b 0.0 a LSD (P=.05) Poa annua injury was rated on a 0-10 scale with 0 representing no injury, a maximum level of allowable injury and 10 dead turf. Days after treatment seven. The Influence of Trimmit on Percent Poa annua Cover and Control (Tables 8 and 8A) Trimmit did not exhibit any level of Poa annua control at any rate within the coastal microclimate found at SFGC (Table 8). Even after receiving eight Trimmit applications at the highest rate of 16 oz/a, Poa annua populations continued to increase throughout the nine-month trial. On the day of the first application (March 0, 00) Trimmit treatment plots at the 16 oz/a rate averaged 6.5% Poa cover. Nine months later following eight Trimmit applications at the 16 oz/a rate, the same plots averaged 5.8% Poa cover.

12 Mark M. Mahady & Associates, Inc. Trimmit SC for Control of Annual Bluegrass in Creeping Bentgrass Putting Greens 1 It is hypothesized that the cool coastal climate creates an ideal moderate environment for the aggressive year-round growth of Poa annua. Under conditions ideal for aggressive growth, Poa annua is less susceptible to the plant growth regulating properties of Trimmit. These moderate conditions are also not ideal for creeping bentgrass, which prefers warmer summer conditions for aggressive growth. Table 8. The Influence of Trimmit SC on Poa annua Cover and Calculated Percent Poa annua Control. Salinas Fairways Golf Course, Salinas, CA. Rick Key, Superintendent. 00. Mark M. Mahady & Associates, Inc. Poa Poa Poa Cover Cover Cover 1 (Control) (Control) Application /0/0 7/0/0 1/11/0 Treatments Rate Schedule DOA1 6DAT 7DAT8 1 Check * *.5 a a 1.8 a (0%) (0%) Trimmit SC.0 oz/a /0, /6, 5/, 6/, 7/0, 9/9, 10/8, 11//0.0 a 7. a. a (1%) (-6%) Trimmit SC 8.0 oz/a /0, /6, 5/, 6/, 7/0, 9/9, 10/8, 11//0 5.5 a 7.0 a.8 a (%) (-%) Trimmit SC 1.0 oz/a /0, /6, 5/, 6/, 7/0, 9/9, 10/8, 11//0 1.5 a 6. a.0 a (%) (-1%) 5 Trimmit SC 16.0 oz/a /0, /6, 5/, 6/, 7/0, 9/9, 10/8, 11//0.8 a 6.5 a. a (%) (-1%) 6 Trimmit + Primo oz/a /0, /6, 5/, 6/, 7/0, 9/9, 10/8, 11//0 9.5 a.5 a 5.8 a (1%) (-10%) 7 Prograss 1.5 EC 8. oz/a /0, /6, 5/, 6/, 7/0, 9/9, 10/8, 11//0 9.0 a 1. a 7.8 a (17%) (10%) LSD (P=.05) Poa annua cover was determined through visual estimation. Calculated percent control versus the untreated check. Days after treatment eight. 5 Under much hotter summer conditions at PRGC, Trimmit exhibited good Poa annua suppression and control (Table 8A). Seven sequential treatments of Trimmit at, 8, 1 and 16 oz/a resulted in statistically significant reductions in Poa annua cover compared to the untreated check days after the seventh application on January, 00. The 16 oz/a rate exhibited 77% Poa annua control, the 1 oz/a rate 6% control, the 8 oz/a rate 68% control, and the oz/a rate 9% control. There would appear to be a critical threshold rate between the and the 8 oz/a Trimmit rates. The tank mix combination of Trimmit at 8 oz/a plus Primo Maxx at 5.5 oz/a also performed very well exhibiting 71% Poa annua control days after the seventh application. Prograss exhibited 55% Poa annua control following six treatments applied at 8. oz/a or 0. gal/a. However, Prograss should never be used on putting surfaces. Prograss caused unacceptable injury to bentgrass in this trial and is not registered for use on putting greens.

13 Mark M. Mahady & Associates, Inc. Trimmit SC for Control of Annual Bluegrass in Creeping Bentgrass Putting Greens 1 Photograph 5. Poa annua control with Trimmit at 16 oz/a (right) versus an untreated check plot (left) days after the seventh application. January, 00. Mark M. Mahady & Associates, Inc. Table 8A. The Influence of Trimmit SC on Poa annua Cover and Calculated Percent Poa annua Control. Poppy Ridge Golf Course, Livermore, CA. Todd Cook, Superintendent Mark M. Mahady & Associates, Inc. Poa Poa Poa Cover Cover Cover 1 (Control) (Control) Application /0/0 8/1/0 1//0 Treatments Rate Schedule DOA1 78DAT DAT7 1 Check * * 1.8 a a.0 a (0%) (0%) Trimmit SC.0 oz/a /1, /8, 5/8, 9/11, 10/9, 11/1, 1/1/0 1.5 a 1. a 17.0 b (1%) (9%) Trimmit SC 8.0 oz/a /1, /8, 5/8, 9/11, 10/9, 11/1, 1/1/0 1.8 a 1.0 a 7.8 c (1%) (68%) Trimmit SC 1.0 oz/a /1, /8, 5/8, 9/11, 10/9, 11/1, 1/1/0 1.8 a 1.8 a 8.8 c (16%) (6%) 5 Trimmit SC 16.0 oz/a /1, /8, 5/8, 9/11, 10/9, 11/1, 1/1/0 1.8 a 10.8 a 5.5 c (0%) (77%) 6 Trimmit + Primo oz/a /1, /8, 5/8, 9/11, 10/9, 11/1, 1/1/ a 11.0 a 7.0 c (8%) (71%) 7 Prograss 1.5 EC 8. oz/a /1, /8, 5/8, 9/11, 10/9, 11/1/ a 1. a 10.8 c (7%) (55%) LSD (P=.05) Poa annua cover was determined through visual estimation. Calculated percent control versus the untreated check. Days after treatment three. 5

14 Mark M. Mahady & Associates, Inc. Trimmit SC for Control of Annual Bluegrass in Creeping Bentgrass Putting Greens 1 Photograph 6. Poa annua control with Trimmit at 1 oz/a (left) and Trimmit at oz/a (right) days after the seventh application. January, 00. Mark M. Mahady & Associates, Inc. It is hypothesized that the much hotter summer temperatures of the inland climate increased the total stress level on Poa annua while creating an environment for more aggressive growth of the creeping bentgrass. These two factors combined with the active growth regulation of Poa annua with Trimmit, changed the competitive balance of the grass stand, favoring the growth of creeping bentgrass over that of Poa annua. The most dynamic reductions in Poa populations at PRGC were observed following the late summer and fall applications. It is possible that properly timed late summer and fall applications serve to control young emerging Poa annua seedlings, which are known to germinate between September and December. At PRGC the finer textured, tighter growing biotypes, which would most likely be characterized as perennial biotypes, appeared to be more susceptible to the growth regulation of Trimmit (Photograph 5), than the more coarse textured annual biotypes (Photograph 6).

15 Mark M. Mahady & Associates, Inc. Trimmit SC for Control of Annual Bluegrass in Creeping Bentgrass Putting Greens 15 Photograph 7. Growth regulation of a perennial biotype of Poa annua following three Trimmit treatments applied at a rate of 1 oz/a. June 7, 00. Mark M. Mahady & Associates, Inc. Photograph 8. Growth regulation of an annual biotype of Poa annua following three Trimmit treatments applied at a rate of 1 oz/a. June 7, 00. Mark M. Mahady & Associates, Inc.

16 Mark M. Mahady & Associates, Inc. Trimmit SC for Control of Annual Bluegrass in Creeping Bentgrass Putting Greens 16 Summary and Practical Perspectives Eight Trimmit treatments applied at rates of, 8, 1 and 16 oz/a during the spring, summer and fall failed to control Poa annua in a creeping bentgrass putting green at Salinas Fairways Golf Course located in the coastal climate of Salinas, California. It is hypothesized that cool coastal climates create an ideal moderate environment for the aggressive year-round growth of Poa annua. Under such conditions, Poa annua is less susceptible to the plant growth regulating properties of Trimmit. Creeping bentgrass prefers warmer summer conditions for active growth and does not grow aggressively under moderate summer temperatures. These factors combined to change the competitive balance of the grass stand, ultimately favoring the growth of Poa annua over creeping bentgrass. Seven Trimmit treatments applied at rates of 8, 1 and 16 oz/a during the spring, late summer and fall resulted in good control (6% to 77%) of Poa annua in a creeping bentgrass putting green at Poppy Ridge Golf Course located in the inland climate of Livermore, California. It is hypothesized that the much hotter summer temperatures of the inland climate increased the total stress level on Poa annua while creating an environment for more aggressive growth of the creeping bentgrass. These two factors combined with the active growth regulation of Poa annua with Trimmit, changed the competitive balance of the grass stand, favoring the growth of creeping bentgrass over that of Poa annua. The most dynamic reductions in Poa populations at the inland location were observed following the late summer and fall applications. It is possible that properly timed late summer and fall applications serve to control young emerging Poa annua seedlings, which are known to germinate between September and December. Continuing to apply monthly treatments of Trimmit during September, October, November and December is recommended in order to maintain consistent growth regulation of newly emerging Poa seedlings. When used in inland microclimates with warm to hot summer temperatures, Trimmit would appear to be a very valuable agronomic tool for the suppression/control of Poa annua in creeping bentgrass putting greens. * * * * *