Economic analysis of creeping bentgrass and annual bluegrass greens maintenance

The costs of maintaining creeping bentgrass and annual bluegrass can vary widely, but annual bluegrass is generally more expensive.

Greens are normally planted to creeping bentgrass, but over time annual bluegrass may encroach and become the dominant species. This will alter playing characteristics and management inputs.
Photos by C. Bigelow

By Cale A. Bigelow, Ph.D.; and W. Tracy Tudor Jr.
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Putting green surfaces and their surrounds are the most critical play area on a golf course because this is where the most strokes occur during a round of golf. The expectations and opinions about maintenance intensity for these areas are highly varied and often hotly debated. In the United States, 47,525 acres (19,233 hectares) of putting green are cultivated, and 27,531 of those acres (11,141 hectares) are creeping bentgrass (Agrostis stolonifera L.) and 10,000 acres (4,047 hectares) are annual bluegrass (Poa annua L.) (6).

Throughout the cool-humid region of the United States — the upper half of the continental United States, east of the Mississippi River and north from northern Tennessee to North Carolina — the most common turfgrass species on greens are creeping bentgrass, annual bluegrass or some mixed species combination (4). Although most golf greens are originally planted using creeping bentgrass, over a period of about five to 10 years, annual bluegrass may become the dominant species. This is true for many older, intensively used golf courses. Mixed species stands are undesirable because they result in seasonally inconsistent conditions. Thus, most golf course superintendents tailor agronomic programs to favor either the creeping bentgrass or annual bluegrass.

Mixed-species greens do not offer consistent playing conditions from season to season as one turfgrass species thrives and the other declines.

There is no perfect grass, and each species has its strengths and weaknesses. Both are capable of forming a persistent, fine-textured, dense, uniform turf under close (less than 0.15 inch [4 millimeters]), frequent mowing. Creeping bentgrass is favored for its high shoot density, ability to self-repair, adaptation to a wide range of climactic conditions and green color. Although rarely intentionally planted, annual bluegrass has very similar characteristics to creeping bentgrass in terms of density and adaptation to intense maintenance. Both species are susceptible to numerous diseases and will require the application of plant protectants to maintain the highest-quality surfaces in the cool-humid region. Annual bluegrass is perceived to be more susceptible to many diseases and less heat- and cold-tolerant than creeping bentgrass. Some other negatives associated with annual bluegrass are its apple-green color and the profuse seedheads produced in spring. These seedheads disrupt surface uniformity and smoothness and ultimately affect ball roll. These concerns, however, should not preclude its use.

Both creeping bentgrass and annual bluegrass are capable of forming a dense turf when maintained intensively.

Regardless of the species grown, a superintendent’s goal is to provide the clientele or membership with putting surfaces that are smooth, firm and true. More important, however, is the ability to provide a persistent and reliable turf in an environmentally responsible manner. In recent years, economic sustainability has also become increasingly important. In the current global economy, superintendents are doing everything they can to improve operational efficiency, but their ability to produce persistent surfaces has become more and more difficult because of weather extremes and budget reductions. Thus, it is only natural to carefully evaluate every aspect of the operation, including the species being grown on putting greens, and ask, “Is this the best choice for our facility and its intended use, and are resources available for maintenance?” For example, the southeastern United States has seen a dramatic shift from creeping bentgrass to the ultradwarf bermudagrasses, which is a better agronomic and economic choice for many facilities.

Rolling greens is a common practice to improve surface smoothness and increase ball roll distances. We estimated that greens would be rolled about 70 times annually for a total cost of about $2,709.

Therefore, the purpose of this article is to provide a frame of reference related to the maintenance inputs and potential costs of cultivating a dominant stand of creeping bentgrass versus annual bluegrass. To our knowledge, no attempt has been made to compare these two species. Economic information has been published comparing other species or comparing the cost of changing to a newer creeping bentgrass cultivar (3,5,9), but no analysis has directly compared creeping bentgrass and annual bluegrass.

Inherent in this undertaking is the recognition of the tremendous variation in putting green management practices and the numerous unique situations that require minimal or substantial inputs. This article is not biased toward one species over the other. Again, it is important to recognize that there is no perfect turfgrass, and one species might be superior to the other based on the prevailing weather, shade associated with cloud cover or fog, supplemental water hardness or salinity, intensity of use and available maintenance resources.

This article applies to golf facilities throughout the cool-humid region and suggests a generalized maintenance calendar and moderate intensity of use for approximately 3 acres of mature putting greens or about 150,000 square feet (~1.4 hectares) of putting greens on sand-based root zones or highly modified sandy soils. Preventive pesticide programs (fungicides and insecticides) and cultural and nutritional programs are intended to promote vigor and growth. As always, there will be exceptions on both the high and low ends of the maintenance budget, facility mission or member expectations that affect final costs.

Mowing, rolling and grooming

A superintendent’s goal is to provide a smooth, true surface, and mowing practices are at the heart of the cultural practices designed to achieve this goal. Most facilities will use a program that combines single- and double-cut mowing in combination with periodic lightweight rolling. These events will vary with the facility’s geographic location, intensity of use and the golfing calendar requirements (for example, club tournaments, etc.).

For the sake of this example and assuming walk-mowing was employed, it was estimated that a superintendent would mow approximately 200 times during a normal growing year (March 1–Nov. 15) and roll about 70 times. A previous survey in the transition zone reported that, on average, 216 mowings were conducted in Tennessee (13). By comparison, for intensively managed Penn A-4 greens in Virginia Beach, Va., mowing — either single- or double-cutting — was reported on 262 days and single rolling on 157 days (9). In addition, superintendents may use grooming practices like brushing and light vertical mowing for both creeping bentgrass and annual bluegrass to promote a more upright growth habit, to stand up annual bluegrass seedheads for thinning during mowing, or to incorporate sand into the turf canopy. This practice may occur four to six times annually.

As shown in Table 1, the costs of mowing and rolling are substantial, more than $60,000 annually, not including the cost of the equipment, depreciation or a skilled maintenance technician. The cost is likely to be similar for the two species. The table also includes estimated annual costs for grooming.

Growth regulation

Although the application of a plant growth regulator (PGR) is not essential, a significant number of superintendents use a PGR to condition surfaces. The reasons for PGR use vary but include reduced vertical growth/clipping management, improved daily/weekly putting green speed consistency, seedhead suppression, environmental stress tolerance and enhanced aesthetic appearance (2). The most widely used PGR is trinexapacethyl, which is sold under many brand names, but was originally released as Primo or Primo Maxx (Syngenta). Application intervals vary considerably depending on the intended goal. For the sake of this article, we assumed that 0.125 fluid ounce of product/1,000 square feet (4 milliliters/100 square meters) is applied every seven to 14 days or approximately every 10 days during peak growth for a total of 12 to 15 times annually (Table 2).

Suppressing annual bluegrass

Superintendents with primarily creeping bentgrass surfaces often seek not only to regulate growth but also to minimize annual bluegrass encroachment. These superintendents may substitute products containing paclobutrazol (Trimmit, Syngenta; Tide Paclo, Quali-Pro) or flurprimidol (Cutless, SePro) for trinexapac-ethyl because these PGRs have been shown to possess suppressive characteristics.

Managers with predominantly annual bluegrass surfaces will most likely use a strictly trinexapac-ethyl program and also apply another PGR to minimize seedheads during the peak spring flush. The presence of seedheads is unsightly and, more important, affects surface smoothness and uniformity. In addition, seedheads can deplete the plant’s carbohydrate (food) reserves. A lack of carbohydrate reserves can negatively affect summer persistence and vigor. The two most common options for seedhead suppression are either a chemical combination/tank-mix of ethephon (Proxy, Bayer) + trinexapac-ethyl, or mefluidide (Embark, PBI/Gordon) (Table 2). Seedhead applications are normally followed by a traditional trinexapac-ethyl regulation program. All of these PGRs are usually applied in conjunction with a liquid fertility program.

Comparing creeping bentgrass to annual bluegrass PGR programs

It is difficult to clearly compare PGR programs for creeping bentgrass to those for annual bluegrass because strategies can vary widely depending on the superintendent’s goals. Annual PGR program costs ranged from $1,364 to $3,860 (Table 2). In general terms, however, managers using a PGR will likely be using trinexapac-ethyl for general regulation, and those with annual bluegrass surfaces will also apply something else in early spring for seedhead suppression. If the assumption is that both managers will be choosing the least expensive PGR, trinexapac-ethyl, for seasonal regulation, then annual bluegrass managers will have slightly higher PGR program costs: $33 to $433, depending on the products they use for seedhead suppression. By contrast, a creeping bentgrass manager using a PGR to suppress annual bluegrass may have much higher costs than a superintendent following a trinexapacethyl-only program. These costs, however, can be reduced by applying the annual bluegrass suppressive PGR only in the “shoulder seasons,” early spring and fall, and substituting trinexapac-ethyl in summer. Although PGRs are an “optional” cost in the overall agronomic program, the potential for reducing the substantial daily mowing requirements may offset their expense.

Sand topdressing is used to dilute surface organic matter and thereby promote firm, smooth surfaces that permit lower cutting heights.

Core aeration and sand topdressing

Core aeration

Firm, smooth surfaces that readily drain are fundamental characteristics for any high-quality putting green. Core aeration is necessary to relieve surface compaction and manage organic matter. Both creeping bentgrass and annual bluegrass have the potential to accumulate excess organic matter in the upper soil profile, which can negatively affect performance over the long term. Thus, core aeration is a traditional fundamental agronomic practice most commonly conducted twice annually, regardless of species. Costs associated with supplemental summer coring (solid tining, venting, water injection, etc.) were not included in the calculation.

Sand topdressing

In addition to core aeration, regular sand topdressing must be applied to offset and dilute surface organic matter and promote firm, smooth surfaces that allow for the lowest practical cutting heights. A reasonable annual target amount of sand topdressing is 15-25 cubic feet/1,000 square feet (0.46-0.76 cubic meter/100 square meters), depending on geographic location. Outside of topdressing in conjunction with core aeration, it is suggested that superintendents regularly apply sand two to three times per growing month at 0.5-0.75 cubic foot/1,000 square feet (0.015-0.029 cubic meter/100 square meters) (Table 3).

It is commonly believed that the extremely high shoot density of the newer creeping bentgrass cultivars makes them more prone to accumulate surface organic matter. In extreme situations, these cultivars may develop a dense organic mat that restricts water and air flow into the soil. Thus, the sand topdressing requirement for creeping bentgrass surfaces in our example was increased by 20% relative to annual bluegrass. The other assumption for this example was that sand would be applied manually using walking spreaders and then broomed/brushed into the surface.

In the example (Table 3), core aeration costs were $3,045, but this figure does not include the costs and fuel usage of the aeration, brushing and mowing equipment. The cost for the two species would not be expected to be different. The real expense is with the sand topdressing, which ranged from $5,300 to $6,625. The higher cost of topdressing for the creeping bentgrass surface would result in a difference of $1,325.

Topdressing materials can be very expensive. Selecting the correct material is an important decision, and sands for putting greens need to be carefully selected based on particle size distribution. In the example (Table 3), we estimated that bulk sand would cost $50/ton. We are aware that some managers are using kiln-dried and bagged sand, which can cost as much as $130/ton and could dramatically affect topdressing costs.

Fertility and nutrition

Adequate fertilization is essential to keep putting greens healthy and minimize damage from environmental and pest stresses. Although the turf requires many nutrients to maintain vigor, nitrogen is the main nutrient that causes a plant response (greening and growth). Fertility programs are highly variable, and rates and application frequency are often tied to intensity of use. In many parts of the cool-humid region like the northeastern United States, annual nitrogen is applied at less than 3 pounds/1,000 square feet (1.5 kilograms/100 square meters) to limit rapid leaf growth and reduce frictional resistance to ball roll (8,16). Higher annual rates are planned where there is more use and/or expected environmental stress and/or pest damage (for example, anthracnose, etc.).

Annual fertility recommendations for mature creeping bentgrass are about 3 pounds/1,000 square feet (1.5 kilograms/100 square meters), but rates for annual bluegrass putting greens vary widely, ranging from 2.7 to 6.3 pounds/1,000 square feet (1.3-3.1 kilograms/100 square meters), with approximately 2 to 3 pounds (1-1.5 kilograms/ 100 square meters) of nitrogen suggested during summer months (1,15). To minimize anthracnose severity, researchers at Rutgers University suggest that soluble nitrogen be spoon-fed and applied at 0.1 pound/1,000 square feet (0.049 kilograms/100 square meters) every seven days (up to 1.2 pounds/1,000 square feet [0.59 kilograms/100 square meters]) starting in May and continuing through the growing season (7). This process of spoon-feeding helps reduce damage and recovery time from disease.

Granular vs. liquid formulations

One suggested fertilizer strategy is to supply the necessary nutrients through both granular and liquid formulations. Granular fertilizers are applied in spring and fall, most likely around cultivation periods, and are intended to supply a background level of nutrients while also correcting any potential soil nutrient deficiencies. Smaller doses of supplemental nutrients are applied in a liquid formulation during peak use periods to promote steady controlled growth. Of all nitrogen sources, urea is the most inexpensive nitrogen source, and provides a consistent and predictable response (12). Remember, extra nutrients in the soil will not make the turf “extra healthy” or more tolerant of stresses, and it is important not to apply excess nutrients that might cause unwanted growth surges or become lost to the environment.

Sample fertility program

As previously mentioned, fertility programs are highly variable. All turf managers know their course and their grasses best, and there is no substitute for experience. There are many successful fertility programs; see Table 4 for an example and a starting point for discussion. This program assumes no major soil nutrient deficiencies, focuses on nitrogen and iron (one of the most widely applied micronutrients), and incorporates a combination of granular and liquid applied nutrients. For annual bluegrass, applications of the liquid formulations of nitrogen should be more frequent in summer to minimize anthracnose. Not included in the program are applications of numerous plant health supplements, biostimulants, phosphites, humic acids, exogenous hormone packages, etc. Their usage, costs and application frequencies vary widely. It is plausible, however, that managers with predominantly annual bluegrass surfaces might be more inclined to incorporate these products into their nutritional programs because this species is perceived to be less tolerant of heat and drought stress.

In this example, annual fertilizer costs ranged from $2,090 to $3,773, with additional costs of ~$1,600 for annual bluegrass, which requires higher overall fertilizer applications (4.3 vs. 3 pounds [2.1 vs. 1.5 kilograms] of nitrogen annually) and the increased labor costs associated with these applications. This extra fertility was included to promote annual bluegrass summer vigor and reduce anthracnose incidence.

Irrigation, soil moisture and soil surfactants

There are many, many philosophies with regard to putting green irrigation management. These vary based on overall turfgrass health, intensity of use, member expectation and other site conditions. The general rule of thumb for irrigation is to supplement rainfall and to practice a “deep and infrequent” management program. Although most golf greens are equipped with an in-ground automatic irrigation system, a superintendent’s goal is to provide a firm surface. This generally means managing root-zone moisture status toward the drier end of the spectrum and supplementing rainfall with timely overhead irrigation for recharging the soil moisture reservoir.

Hand-watering and syringing

Superintendents also hand-water and syringe to compensate for differences in micro-environments, surface undulations and summer stress periods. The main goal is to provide putting green conditions that are as uniform as possible, and relieve afternoon stress. This practice is labor-intensive and highly variable depending on the turfgrass species and soil conditions. The values in Table 5 do not include supplemental overhead irrigation costs.

Like mowing, which is also highly labor-intensive, hand-watering and syringing can become expensive (>$15,000 annually). Moisture management is critical to turfgrass survival during stressful summer months and requires skilled and dedicated employees. However, the cost difference between annual bluegrass and creeping bentgrass appears substantial, as the additional attention required in the afternoons for “late-afternoon wilt watch” for annual bluegrass adds up to more than $4,500 annually (Table 5).

Soil surfactants

Like PGRs, soil surfactants are optional in an agronomic program, but many superintendents may apply soil surfactants to improve the moisture status of a putting green and promote greater uniformity. Further, many sand-based surfaces are prone to the formation of localized dry spots that may require additional manual attention to remedy or water during stress periods. A soil surfactant program can help reduce these needs. The annual costs for one of these programs ranges from $1,880 to $2,720, and there would be no expected cost difference between species (Table 6).

Superintendents supplement general irrigation with handwatering and syringing. Late-afternoon syringing or “wilt watch” during periods of heat stress or drought is labor-intensive and potentially costly.

Weed suppression

Few herbicides are labeled for use on greens, and most superintendents will not risk potential injury from a herbicide application. Where small populations of weeds occur (for example, chickweed, white clover, pearlwort, etc.), they are often physically removed by hand or affected areas are plugged out. On occasion superintendents with creeping bentgrass greens may treat for moss or algae. In addition, some may apply a pre-emergence herbicide like bensulide in late summer to suppress annual bluegrass. These concerns, however, are not common to all greens. The cost for these programs is $1,873 (Table 7).

Insect control

For insect suppression, putting greens in the cool-humid region are frequently treated for white grubs, black turfgrass ataenius and surface-feeding insects that include a number of caterpillars like black cutworms and armyworms. Throughout much of the northeastern United States, superintendents who manage annual bluegrass greens must consider the potential for damage from the highly destructive annual bluegrass weevil (Listronotus maculicollis), which has become one of the most difficult-to-manage insect pests on golf courses because of its multiple generations and insecticide-resistant populations. Annual bluegrass treatment would result in $2,402 in additional costs (Table 8).

Anthracnose is a common disease in annual bluegrass greens. Best management practices suggest employing a preventive fungicide program and weekly liquid nitrogen applications during the summer months.
Photo by A. Moeller

Disease management

Both creeping bentgrass and annual bluegrass are inherently susceptible to numerous diseases. The occurrence and severity of these diseases is a function of both the specific growing environment and the cultural management intensity that may impart additional stress on the turfgrass plant and render it more susceptible to disease (4). Maintaining a dense, persistent and smooth putting surface that is free of scars and pits that may develop as a result of disease is important not only for maintaining golfer satisfaction but also for maintaining turf health and vigor, which ultimately result in stand persistence during environmental stress periods.

A general program

A very general preventive fungicide program for both species would include fungicides for the fungal pathogens that cause dollar spot, Rhizoctonia brown patch and Pythium blight. In the cool-humid region, the most chronic disease problem is dollar spot. Regardless of the disease, research has shown a strategic preventive fungicide program implemented before peak disease pressure is more effective and cost-effective than a curative program (10). Diseases like brown ring patch, fairy ring, Pythium root dysfunction/rot, take-all, summer patch of creeping bentgrass, the recent very serious summer decline phenomenon (for example, bacterial wilt/Acidovorax) and algae are not specifically targeted in this program. For annual bluegrass, a fungicide program and aggressive fertility program preventively address anthracnose and summer patch concerns. A spring disease cleanup spray (Microdochium patch, dollar spot, leaf spot) and a season-closing spray for snow mold would be optional inclusions.

Anthracnose and summer patch

The fundamental difference between species is the concern with anthracnose and summer patch. For optimal health, other researchers (14) suggest a preventive program for annual bluegrass greens that starts applications for summer patch and anthracnose early when average soil temperatures exceed 65 F-68 F (18 C-20 C). DMI fungicides are useful at this time, and application intervals of 14 to 28 days are appropriate when disease pressure is low. Application intervals of seven to 14 days are recommended when there is significant summer stress or high disease pressure. The program would include rotating various chemical classes to minimize fungicide resistance and products in general fungicides like fludioxonil (Medallion, Syngenta) and the DMI fungicides metaconazole (Tourney, Valent), propiconazole (Banner Maxx, Syngenta), tebuconazole (Torque, Cleary) and triticonazole (Trinity, BASF) have been shown to provide the best overall control. Since chlorothalonil has shown no resistance issues, it is recommended that this fungicide should be incorporated primarily during the summer applications.

Fungicide costs

Like fertilizer programs, fungicide programs, products, application intervals, etc., for creeping bentgrass and annual bluegrass may vary widely. In our example preventive fungicide program, costs ranged from $8,482 to $21,524 (Table 9). A basic program for creeping bentgrass with 11 sprays could cost $8,482, while a more aggressive program with 16 applications might cost $18,384. By contrast, an aggressive preventive program for annual bluegrass and a focus on anthracnose with 19 total sprays might cost $21,524. The increased spray schedule would be associated with very closely mowed surfaces grown in a difficult (hot-humid) growing environment and includes numerous and closely spaced (for example, seven-day intervals) applications. In addition, a suggested best management strategy for minimizing the severity of anthracnose is to encourage steady growth. This is accomplished by applying readily soluble nitrogen sources at low rates (for example, 0.1 pound nitrogen/1,000 square feet [0.49 kilogram/100 square meters) every seven days from late May through August. Superintendents will likely add a fungicide with this spray as an insurance policy against disease. These extra sprays would result in as many as eight to 10 weekly sprays during the summer specifically for the suppression of anthracnose.

By contrast, a fungicide program for creeping bentgrass would focus on dollar spot, the most chronic disease problem. The vast majority of greens were originally planted using Penncross bentgrass. This cultivar is moderately susceptible to dollar spot and damaged by multiple seasonal outbreaks (11). It is conceivable that significant fungicide and labor/fuel reductions could be made if those creeping bentgrass surfaces were renovated to a more disease-resistant cultivar like Declaration, 007, and others.

Looking forward

Maintaining putting greens can be costly, but many would argue that it is worth the labor and expense to produce a quality golf experience. It is difficult to put an exact number or generalized cost on golf green management regardless of the species being maintained. What we have calculated is intended to be a starting point for discussion, and we recognize that program costs vary widely for many reasons. In our example, annual bluegrass appears slightly more expensive to maintain than creeping bentgrass (Table 10).

Not surprisingly, the biggest expenses for both species are associated with general maintenance (mowing, rolling, supplemental irrigation and core aeration/topdressing). The difference in species-related expenses is associated with strategies or needs for supplemental afternoon syringing to minimize summer stress, additional fertility inputs and preventively managing troublesome pests like anthracnose, summer patch and annual bluegrass weevil. These may not be issues at every facility, but they certainly need to be considered. Furthermore, with recent environmental extremes in the cool-humid region, annual bluegrass persistence issues in both winter and summer have been amplified, making it even more stress-prone.

As stated in the beginning of this article, there is no perfect grass, but golf is played on natural grass, and golfers and golf facilities are fortunate to have skilled, enthusiastic superintendents who are willing to dedicate themselves to green maintenance. Individual species and cultivar selection comes at a cost, but today there are more options than ever. As turfgrass breeders continue to introduce new germplasm with greater pest resistance and environmental tolerances, creeping bentgrass inputs could decrease. For annual bluegrass, unfortunately, these breeding efforts have not been as strong and limit choices in improved annual bluegrass. It is possible that alternatives like the velvet bentgrasses and perhaps even fine fescues might become common in certain locations.

Finally, as superintendents evaluate their agronomic toolbox and carefully consider the economics associated with using the various tools, species and cultivar selection should be a fundamental underlying consideration. If financial resources are declining and putting green quality is suffering, perhaps it is time to carefully consider alternatives to the current species or cultivar. We hope you find this article helpful and welcome your thoughts and future success stories.

Disclaimer

Mention of brand names and products is purely for example. Purdue University does not endorse or promote any product mentioned in this article to the exclusion of others.

Acknowledgments

The costs/prices listed in this publication were determined after consulting with numerous industry representatives who included experienced golf course managers across the region, fertilizer and pesticide company representatives, regional agronomists and other industry practitioners. We are indebted to their knowledge and willingness to share their expertise.

Literature cited

1. Beard, J.B., P.E. Rieke, A.J. Turgeon and J.M. Vargas Jr. 1978. Annual bluegrass (Poa annua L.) description, adaptation, culture and control. Research Report 352. Michigan State University Agricultural Experiment Station, East Lansing, Mich.

2. Bigelow, C.A. 2012. Plant growth regulators in bentgrass turf areas: Thoughts and trends in the use of a valuable management tool. USGA Green Section Record 50(8):1-4.

3. Davis, M. 1982. Comparing maintenance costs: bentgrass versus bermudagrass greens. USGA Green Section Record 20(1):5-7.

4. Dernoeden, P.H. 2012. Creeping bentgrass management. 2nd edition. CRC Press, Boca Raton, Fla.

5. Fry, J., M. Kennelly and R. St. John. 2008. Zoysiagrass: economic and environmental sense in the transition zone. Golf Course Management 76(5):127-132.

6. Lyman, G.T., C.S. Throssell, M.E. Johnson et al. 2007. Golf course profile describes turfgrass, landscape and environmental stewardship features. Applied Turfgrass Science Online. www.plantmanagementnetwork.org/pub/ats/research/2007/profile/(doi:10.1094/ATS-2007-1107-01-RS).

7. Murphy, J.A., J.C. Inguagiato, B.B. Clarke et al. 2007. Cultural management of anthracnose disease on annual bluegrass: Nitrogen fertility and growth regulators can have positive impacts on management of this potentially devastating disease. USGA Green Section Record 45(6):8-13.

8. Radko, A. 1985. Have we gone too far with low nitrogen on greens? USGA Green Section Record 23(2):26-28.

9. Robinson, C. 1998. A-4, not your parents’ bentgrass: New management techniques for a new bentgrass variety. USGA Green Section Record 36(5):16-18.

10. Royals, J.K. II, S.B. Martin, J.J. Camberato and S.N. Jeffers. 2005. Development and evaluation of strategic fungicide programs for control of warm weather diseases in creeping bentgrass. International Turfgrass Society Research Journal 10:237-246.

11. Ryan, C.P., P.H. Dernoeden and A.P. Grybauskas. 2012. Seasonal development of dollar spot epidemics in six creeping bentgrass cultivars in Maryland. HortScience 47(3):422-426.

12. Settle, D., and P.H. Dernoeden. 2009. Evaluation of cytokinian plant extract biostimulants, iron, and nitrogen products for their effects on creeping bentgrass summer quality. Online. USGA Turfgrass Environmental Research Online 8(1):1-15.

13. Strunk, W.D. 2006. Mowing and light-weight rolling of creeping bentgrass (Agrostis stolonifera L.) putting greens during summer heat stress periods in the transition zone. Masters thesis. University of Tennessee, Knoxville.

14. Tredway, L., and F. Wong. 2012. Managing anthracnose with fungicides: The future for anthracnose management looks brighter with new chemistries and an integrated management approach. Golf Course Management 80(6):90-96, 98.

15. Vargas, J.M., and A.J. Turgeon. 2003. Poa annua: physiology, culture and control of annual bluegrass. J.H. Wiley and Sons, Hoboken, N.J.

16. Zontek, S.J., D.A. Oatis, D. Bevard et al. 2010. Does the grass know the cost? Don’t get your green thumb by handing over cash. USGA Green Section Record 48(3):32-36.


Cale Bigelow (cbigelo1@purdue.edu) is an associate professor in agronomy and turfgrass science and W. Tracy Tudor is a graduate research assistant in turfgrass science at Purdue University, West Lafayette, Ind.