Comparative Responses of Poa annua Biotypes From Golf Greens to PGR and Herbicide Treatments.

Poa annua patches on golf course greens, which may represent different biotypes, are commonly observed to differ in regards to color, texture, growth rate, and number of seed heads.  It is not known whether these visual differences are promoted by management strategies and/or whether morphologically diverse Poa annua plants respond differentially to control programs. We conducted a greenhouse study to examine whether visually different Poa annua phenotypes responded differently to chemical treatments.  Poa annua plants were collected in 2011 from greens at the Lexington Country Club and The University Club of Kentucky, both located in Fayette County Kentucky, and grown in a greenhouse. The plants were collected based on their having one of two appearances while being on the same green: 1. Dark green, with few to no flower heads (“dark” biotype) or 2. Light green, with numerous flower heads ("light" biotype).  Treatments were as follows: paclobutrazol (270 g a.i./ha applied every 3 weeks); flurprimidol (490 g a.i./ha applied every 3 weeks); bispyribac-sodium (25 g a.i./ha applied once at the beginning and the end of the study); and amicarbazone (49 g a.i./ha applied weekly for the first 4 weeks).  The experiment was repeated with the same plants in 2011 and 2012.  In 2011, bispyribac-sodium reduced the quality of the “dark” biotypes more than the “light” biotypes from both the University Club and the Lexington Country Club.  Paclobutrazol and flurprimidol reduced the quality of the “dark” biotypes more than the “light” biotypes from the University Club.  However, in 2012, flurprimidol reduced the overall quality of the “light” biotypes from the Lexington Country Club more than those collected from the University Club. These results demonstrate the potential for different responses between Poa annua biotypes to PGRs and herbicides and that these differences, like all things about Poa annua, may be complex.