Influence of Cultural and Chemical Management Strategies on Annual Bluegrass Populations on Golf Course Putting Greens.
Open Access
- Author:
- Han, Kyung Min
- Graduate Program:
- Agronomy
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- July 02, 2012
- Committee Members:
- John Edward Kaminski Iii, Thesis Advisor/Co-Advisor
- Keywords:
- Annual bluegrass
Creeping bentgrass
Trinexapac-ethyl
Flurprimidol
Iron sulfate
Amicarbazone
Methiozolin
Bispyribac-sodium - Abstract:
- Annual bluegrass (Poa annua L.; ABG) is widely adapted to most growing environments and is often considered a weed on creeping bentgrass (Agrostis stolonifera L.; CBG) golf course putting greens. Undesirable characteristics of ABG include its light-green color, prolific seedhead production, shallow root system, high susceptibility to various pathogens and poor tolerance to extreme temperatures (Vargas and Turgeon, 2004). Although various strategies have been implemented to eradicate ABG, its control has proven elusive. Recent interest in a programmatic approach to suppressing ABG has been gaining popularity among golf course superintendents throughout the United States and golf courses in Europe and Australia. Generalities of this program include: 1) low seasonal nitrogen (N) rates; 2) the use of Class B plant growth regulators (PGRs); and 3) routine applications of iron sulfate. Additional commonalities of the program include minimal disturbance to the soil profile, routine sand topdressing, relatively low mowing heights and limited phosphorous fertilization. The claimed benefits of the program include reductions in ABG populations and disease incidence and severity. The impact of these strategies on the short and long-term health of the turfgrass system remains unknown. A two-year field study was initiated to evaluate the influence of N rates (24 or 108 to 147 kg N ha-1 year-1), PGRs (trinexapac-ethyl, flurprimidol, and none) and iron sulfate rates (0, 12, and 49 kg Fe ha-1 application-1) on ABG populations. Annual bluegrass populations were influenced by varying chemical and cultural management practices. In general, ABG populations were lower when treated with low seasonal N rates, flurprimidol and high rates of iron sulfate. Although the impact of these programs on disease activity was minimal in 2010, turfgrass receiving lower seasonal N rates generally had less dollar spot throughout 2011. In addition to the cultural and chemical management programs for suppressing ABG, new herbicides continue to be introduced. Limited information on the efficacy of these products on suppressing diverse biotypes of ABG typically found on golf courses is available. A second objective of this thesis was to evaluate the ability of commercially available and experimental herbicides to control a variety of ABG biotypes. A pot study was conducted to evaluate the ability of amicarbazone, methiozolin and bispyribac-sodium to suppress 30 to 31 annual and perennial biotypes of ABG. Control of ABG with amicarbazone was rapid and generally, all biotypes were suppressed within 3 to 6 weeks after the initial application. A slower suppression of ABG was observed when ABG was treated with methiozolin and bispyribac-sodium. While amicarbazone and methiozolin generally provided nearly complete control of all ABG biotypes evaluated in this study, variation in ABG suppression was exhibited with bispyribac-sodium. In areas where ABG populations are low and/or where rapid suppression is desired, amicarbazone may be utilized. In situations where ABG populations are relatively high, methiozolin or bispyribac-sodium may allow for a slower conversion to a more desirable species such as CBG. Based on results, the manipulation and suppression of ABG may be achieved through a combination of chemical and cultural practices. The long-term impact of these non-traditional programmatic management programs, however, remains unknown. Additionally, the safety and field efficacy of relatively new herbicides must be evaluated to ensure the safe use of these products on desirable turfgrass species grown on golf courses.