Effects of Multiple Applications of Plant Growth Regulators and Selected Herbicides on Poa annua L. var. reptans Hausskn. Reduction in Creeping Bentgrass.

Perennial annual bluegrass (Poa annua L. var. reptans Hausskn.) (ABG) remains one of the most difficult weed problems golf course managers have in creeping bentgrass (Agrostis stolonifera L.)  (CB)  greens and fairways.  There are limited options available for selective and unobtrusive ABG control. Same-site studies were conducted over  two or three years on fairway and green height CB to test the effects of  one herbicide and three plant growth regulators for gradual reduction of ABG.  The tests were conducted near Lexington, KY from 2005 through 2007.  Paclobutrazol and flurprimidol were shown to significantly reduce ABG in CB while at the same time having a significant positive effect on CB quality.  Trinexapac-ethyl increased overall quality of the bentgrass – Poa turf, but actually increased ABG in all tests.  Bispyribac-sodium was shown to have no significant effect on long term reduction of ABG without also producing undesirable effects on CB.  Consistent and long-term applications of either flurprimidol or paclobutrazol can significantly and selectively remove ABG from CB at both putting green and fairway heights, the key factor being regular and consistent timing of applications.