Convert your fairway to bentgrass

During the 1960s and '70s, most golf-turf research focused on the management of putting greens. Improved chemical and mechanical cultural practices, irrigation management, root-zone mixes and equipment, as well as the development of bentgrass varieties better adapted to close mowing, have caused things to progress to the point that "good" greens are almost a given. Superintendents rebuild greens that they cannot successfully manage or, at a minimum, re-grass them.

During the past several years, however, research emphasis has shifted toward improving the playability of fairways. Researchers, superintendents and the industry in general have become fully engaged in the development of new and better equipment, irrigation systems, herbicides, plant growth regulators (PGRs) and improved turfgrasses to improve the quality of fairways.

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Root-zone modification provided the solution to many management problems on greens.

Likewise, some superintendents have used core cultivation followed by topdressing to improve root-zone soil conditions on some fairways. However, this is a significant undertaking. Another option is to convert your fairway to a new turfgrass variety.

What should your objective be? High-quality fairway turf should be dense and upright, able to withstand relatively close mowing and recover quickly in landing areas. It also should have slow vertical growth and still be able to compete aggressively with unwanted species, without excessive thatch production. This is a significant wish list and, at this time, no turfgrass variety exists that can provide all of these qualities with a high level of satisfaction. Therefore, it is necessary to prioritize. You must carefully consider the decision to convert an existing fairway to another variety and identify a clear set of long-range objectives with regard to future management practices. Can you maintain the variety you convert to after you have made the conversion? Do you have a firm commitment to the financial needs of managing the converted turf? Last, but not least, can you convert the new turf to something else if it does not work out?

The reasons for converting a fairway to some other variety are many and varied. The common thread that runs through all of them, and that often surfaces as the top priority, is the desire to mow at 0.5 inch or less. Being able to mow closely is not only a function of the turfgrass species but of the terrain as well. Many older golf courses do not have fairways smooth enough to accommodate the close mowing for which many golfers ask. Consequently, scalping and other indicators of poor mowing quality frequently become serious issues. In such situations, fairway conversions must include the physical elimination of the existing turf coupled with surface re-grading. Although extreme and expensive, this approach usually is successful.

At the other end of the conversion spectrum is the simple tactic of overseeding the desired species into the fairway during periods when the existing turf is under environmental stress and, therefore, less competitive.

The balance of this article will discuss the various methods you can use to convert fairway turf. The method you choose depends on the answers to the questions listed above.

Site-specific needs Every conversion has an element of site specificity. Indeed, within an individual golf course, conversion tactics could vary from fairway to fairway depending on existing conditions and the species composition of the turf.

For example, assume that your objective is to replace existing fairways of predominantly annual bluegrass with turf that is predominantly creeping bentgrass. In such a scenario, it is probable that your recent management of these fairways included the use of lightweight mowers, clipping collection and perhaps the use of PGRs. Such management tactics can result in a highly variable grass population from fairway to fairway, depending on how long you've employed this management regime. In those areas where some creeping bentgrass was present in the beginning, the bentgrass population may have increased significantly. However, in those areas where bentgrass was scarce, only slight or modest increases will have occurred.

To maximize the conversion to bentgrass in such a situation, the methods you employ must, first of all, preserve the existing bentgrass. Therefore, it is advantageous to map each fairway to delineate those areas that already are predominantly bentgrass vs. those areas that remain predominantly annual bluegrass. Once you've completed the mapping, you can complete the conversion in a more selective and specific way, concentrating on those areas where minimal bentgrass exists.

Merely overseeding bentgrass into existing vigorous annual bluegrass is a consummate waste of bentgrass seed. A successful "catch" of bentgrass depends on the existing annual bluegrass being non-competitive (either dead, seriously stressed or chemically suppressed). When the annual bluegrass is non-competitive, you can readily introduce the bentgrass for a significant stand conversion. An important point to remember about overseeded bentgrass is that it takes time before it begins to make an appearance. In most cases, the real evidence of overseeding success is not clearly obvious until the second year after you've begun the process.

Different tactics exist to suppress annual bluegrass that is not dead or significantly stressed. The most common method is to suppress it with a growth regulator before or after overseeding. Chemical suppression of the existing annual bluegrass should be with a material that has no soil activity. This is important because the germinating overseeded bentgrass will grow much more easily without a suppressing agent in the soil.

Renovation One method that superintendents use successfully is as follows: * Core cultivate at least three times.

* Verticut and drag the cores.

You can do this much to all the fairways without altering the existing turfgrass population. The following additional tactics are appropriate for those portions of the fairways that are predominantly annual bluegrass.

* Overseed the new bentgrass variety with a groove seeder in at least two directions, and also broadcast the seed at 0.25 pound of seed per 1,000 square feet. It is unwise to overseed at a rate in excess of 0.75 pound per 1,000 square feet--the crowding this causes will delay the maturation of the bentgrass (delayed stolonization).

* Four days after overseeding, apply trinexapac-ethyl (Novartis' Primo PGR). Use a rate of 0.5 ounce per 1,000 square feet for the EC formulation or 0.25 ounce for the WSB formulation. You can closely mow the treated areas before the application.

The suppression of the existing turfgrass canopy should last for about 5 to 6 weeks, while the bentgrass should germinate within a day or two of the Primo application. As a result, the bentgrass seedlings should be at the three- to four-leaf stage and competitive before the annual bluegrass begins to outgrow the chemical suppression of the Primo application.

Conversion for mixed stands On many golf courses in the Mid-Atlantic and northeastern United States, the fairway turf is a combination of cool-season species. Usually, annual bluegrass is present and often is the predominant species. On a limited number of courses, zoysia is the primary species. Over the past 25 years, the most common fairway conversion has been to perennial-ryegrass blends. Primarily, this choice has evolved because of the herbicide ethofumesate (AgrEvo's Prograss) and its ability to control annual bluegrass both pre- and post-emergently. Plus, breeders are steadily releasing new varieties with increased disease resistance, adaptability to close mowing and better mowability. Also, manufacturers have introduced a series of new fungicides for the control of the diseases that plague perennial ryegrass.

However, during the past 3 years, the weather has created significant problems for perennial ryegrasses. Gray leaf spot has become a major disease problem in many locations during the summer, and losses due to winter problems (particularly ice damage) also have occurred. As a result, many courses now are converting to creeping bentgrass.

* Favor bentgrass with PGRs. If the fairway is mostly bentgrass (greater than 60 percent), alternatives to a complete renovation exist. However, as a management foundation, you must commit to lightweight mowing, clipping removal and making most of the nitrogen in the fertilization program available to the turf when the creeping bentgrass is most actively competing against the annual bluegrass (June, July or August). Available nitrogen at other times of the year favors the competitiveness of annual bluegrass.

With this management foundation in place, you can complete a conversion without overseeding. Research has shown that the use of PGRs such as paclobutrazol (Scotts' TGR) can selectively suppress the annual bluegrass and thereby increase the amount of creeping bentgrass (some other PGRs also may be suitable for this purpose). Application timing is important and should coincide with the growth cycles of the two species. For example, annual bluegrass is physiologically weakened after it produces seedheads in late spring. This time of year is also coincident with the first soil-temperature-driven creeping-bentgrass growth. Application of a PGR at this time can effectively enhance creeping-bentgrass competitiveness. Coupled with available nitrogen, the creeping bentgrass can make significant increases during the summer months.

In the fall, just after annual bluegrass begins to germinate, but before creeping bentgrass growth slows due to lower light intensity and cooler soil temperatures, another PGR application is advantageous. This application timing slows the growth of the annual bluegrass at a time when it normally becomes more competitive. In addition, any newly germinated annual-bluegrass plants have difficulty becoming established, and those yet to germinate will be stunted after they do.

* Favor bentgrass with herbicides. Another approach you can use when creeping bentgrass is the predominant species is fall applications of Prograss. Although you cannot use the higher rates (typical for perennial ryegrass) without injury to creeping bentgrass, you can apply lower rates sequentially. Application of 0.75 pounds of active ingredient per acre in late September, late October and late November (if possible) are effective in reducing annual-bluegrass populations in creeping bentgrass. This might cause some slowness in spring greenup in creeping bentgrass but no long-lasting injury or thinning. The Prograss approach has particular merit where the annual bluegrass germinates throughout the winter months. Prograss is an effective pre-emergent for annual-bluegrass control. It has post-emergence activity as well, but its strength is as a pre-emergent.

When you overseed as part of the conversion program, the use of Primo as described earlier is the preferred tactic: Both Prograss and TGR can interfere with the successful introduction of creeping bentgrass via overseeding.

When the creeping bentgrass is less than 50 percent of the stand, and lightweight mowing and clipping removal have not successfully increased the population, you may need to use more drastic measures. Superintendents have used applications of non-selective herbicides such as glyphosate (Monsanto's Roundup Pro) or glufosinate-ammonium (AgrEvo's Finale) to convert fairway turf, particularly when annual bluegrass or perennial ryegrass is the predominant and undesired species.

These compounds have no activity on the annual-bluegrass seed in the soil. However, by using aggressive core cultivation, verticutting and dragging after the existing turf dies, you can establish significant creeping-bentgrass populations with groove and broadcast seeding. If you perform this operation when the soil temperature is above 70°F, the germination rate of annual bluegrass will be lower than when the soil temperature is below 70°F. In most cases, the resulting turf will be predominantly creeping bentgrass. This then provides the opportunity to embark on a program, as I described, for locations where the creeping bentgrass is 60 percent or more of the population.

Recently, interest in converting fairways to Kentucky bluegrasses has increased. Breeders are releasing new varieties that offer many of the attributes golfers look for in high-quality fairway turf, including greater tolerance of relatively low mowing heights. We need more research in this area, but such a conversion has considerable merit and may well be a successful solution for some situations. As with creeping bentgrass, you could introduce Kentucky bluegrass into existing fairways with several methods. A total vegetative kill would probably bring about the quickest conversion, as most fairways have little existing Kentucky bluegrass with which to work.

More methods exist for converting fairway turfgrass species than I can discuss in this article. However, the most important thing is to focus on your ultimate management objective as the long-term plan for the fairway turf. Once you choose a course of action, stick to it. Being consistent will lead to success, while wavering and changing your approach in the middle of the project usually spells disaster.

Dr. Thomas L. Watschke is professor of turfgrass science at The Pennsylvania State University (University Park, Pa.).

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