Glyphosate Efficacy as Influenced by Cultivation Practices on a Creeping Bentgrass Fairway Turf

Glyphosate is routinely used to eradicate existing turf in golf course fairway renovations. However, current label recommendations suggest delaying cultivation of glyphosate treated areas for 7 days. A 2-year held study was conducted to assess how various seedbed preparation techniques (i.e., verticutting, core-cultivation, or verticutting + core-cultivation) influence glyphosate efficacy on creeping bent grass fairway turf when completed at various intervals shortly after application [0-7 days before cultivation (DBC)]. Percent green cover declined from initial values of approximate to 90% to <= 0.2% at the end of the study after glyphosate application at all timings, regardless of cultivation during both years. All cultivated plots had 37.9% to 72.3%, or 5.9% to 62.3% less green cover compared with non cultivated plots when glyphosate was applied <= 3 days before cultivation in 2014 and 2015, respectively. Generally, the number of days until green cover reached 1% (GC,) ranged from 6.6 to 11.1 in 2014 and 5.2 to 6.9 in 2015. Within glyphosate application timings, no differences in GC(1) were observed between cultivated and non cultivated treatments in 2014, except at 0 DBC. The GC(1) for verticutting was 5.1 days longer than non cultivated plots; however, all other cultivation treatments were equivalent to non cultivated plots when glyphosate was applied 0 DBC. All cultivation treatments reduced GC(1) 1.7 to 2.5 days compared with the no cultivation treatment, regardless of glyphosate application timing in 2015. Results from this study indicate that cultivation of creeping bent grass fairway turf within 7 days of glyphosate application is not detrimental to long-term herbicide efficacy, and in some cases may actually enhance the rate of decline of glyphosate treated creeping bent grass.