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Conversion of Golf Course Fairways Without Using Nonselective Herbicides

Zac Reicher and Glenn Hardebeck

Objective

Determine an efficient system of converting golf course fairways to creeping bentgrass without using a nonselective herbicide.

Rationale

Using a nonselective herbicide to convert golf course fairways to creeping bentgrass necessitates closing the fairway for extended periods resulting in inconvenience for golfers and a decrease in revenue. A gradual conversion process over multiple years using overseeding would eliminate this problem.

How It Was Done

Over multiple years, Penneagle creeping bentgrass is seeded into freshly aerified fairways at 0, 1.0, or 2.0 lbs seed/1000 ft² in early September, April, or September and April of each year. Prior to seeding, plots are treated with trinexapac-ethyl (Primo) at 0, 0.5, and 1.0 oz/1000 ft² to reduce competition from the established plants. This study is located at the Agronomy Research Center on a perennial ryegrass stand and on #6 fairway of the Purdue Ackerman Golf Course on a primarily Poa annua stand. Monthly ratings on bentgrass cover and visual quality are recorded throughout the growing season. The overseeding treatments have been applied in September of 1995, 1996 and 1997 and in April of 1996 and 1997. One more overseeding will occur in April 1998, and data will be recorded throughout the 1998 growing season.

Results to Date

• The success of overseeding depends on the type of turf that will be overseeded. Creeping bentgrass established and is spreading in many of the treatments at the Agronomy Research Center in a perennial ryegrass stand. However, in the Poa annua fairway at the Ackerman Course, no bentgrass has survived outside of control plots that were sprayed with Roundup and seeded in fall 1995 and spring 1996. This indicates that it is very difficult, if not impossible to convert a fairway from Poa annua to creeping bentgrass without using Roundup and reseeding.

• In the perennial ryegrass at the Agronomy Research Center, seeding in the fall only was as effective as seeding in the spring and fall, and far more effective than seeding in the spring only (Table 5).
• There is little benefit from increasing the seeding rate from 1.0 to 2.0 lbs/1000 ft² (Table 6). However, 1.0 lb/1000 ft² is far superior to 0.75 lb /1000 ft² used in a previous study.
• Applications of trinexapac-ethyl improved visual quality shortly after application in both spring and fall (Table 7 and 8). This improvement was due to a number of factors depending on location and the time of year. The spring application of trinexapac-ethyl reduced the "steminess" and poor mowability that is typically seen on perennial ryegrass in late spring. The spring application of trinexapac-ethyl on the annual bluegrass on the Ackerman Course fairway reduced the visibility of seedheads giving a much better appearance than the untreated annual bluegrass. Trinexapac-ethyl applied in Sept. turned the treated plants a slightly darker green.
• There has been no discernible increase in bentgrass establishment due to the trinexapac-ethyl application, regardless of rate.
• The ratio of bentgrass to Poa annua fluctuates tremendously over the course of a year because the competitiveness of each species changes with the weather (Fig. 1). Determining how much Poa annua and/or creeping bentgrass is present in a fairway is the very first step in determining if and how renovation should be attempted. A Poa annua problem might be overstated if judged in late Spring or late fall, or understated if judged in late summer.

The next scheduled seeding treatment for this study is in spring 1998 and data will be recorded from this study throughout the summer 1998.

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Send corrections, suggestions, and comments to biehlj@purdue.edu