FINE FESCUE VARIETAL TOLERANCE TO GLYPHOSATE RATES. M.C. Cox*, S. Askew, W. Askew, and J. Goatley Jr., Virginia Tech, Blacksburg, VA (43)


As the current economic turn down affects golf budgets, more scrutiny is placed on managed turf areas to reduce fertility and mowing costs.  Nonmow areas, or secondary roughs, are a cost effective and visually appealing approach to maintaining out-of-play areas on the golf course.  Fine fescues are typically used for these areas because they are shorter than other grasses and tend to allow golfers to find and advance errant shots.  A unique set of weeds exist in nonmow situations and weed control programs are lacking.  Some fine fescues have demonstrated tolerance to glyphosate in past research, and glyphosate would be a valuable tool for controlling various perennial grass weeds in nonmow areas.  More information is needed to determine which fine fescue varieties are more tolerant to glyphosate and how glyphosate rates affect visual quality and seedhead production of fine fescues.  The objective of this study was to evaluate glyphosate at 0.6, 0.8, and 1.4 kg ai/ha for effects on visual quality, NDVI, and seedhead production of 56 fine fescue varieties. 

Glyphosate was applied at 0.6, 0.8, and 1.4 kg ai/ha with an 18 inch wide sprayer on May 16, 2011.  The 56 fine fescue varieties were comprised of 1 sheep fescue, 3 slender creeping fescues, 12 hard fescues, 13 chewings fescues, and 27 strong creeping fescues.  All plots were mowed in April approximately 5 weeks prior to treatment and not mowed again for the duration of the study.  Glyphosate injured fine fescue most at 1 month after treatment.  At this timing, 22, 9, and 2 varieties maintained acceptable quality when treated with 0.6, 0.8, and 1.4 kg ai/ha glyphosate, respectively.  Of the 22 varieties that maintained acceptable quality 1 month after 0.6 kg ai/ha glyphosate, 12 were hard fescues, 8 were strong creeping, 1 was a slender creeping, and 1 was a sheep fescue.  The following 7 hard fescue and 1 sheep fescue varieties maintained acceptable quality 1 month after 0.8 kg ai/ha glyphosate: SPM, Pick HF#2, Berkshire, Quatro, IS-FL 28, Scaldis, SRX 3K, Oxford, and Heron.  Only Quatro sheep fescue and Oxford hard fescue maintained acceptable quality 1 month after glyphosate at 1.4 kg ai/ha.  When not treated with glyphosate, the following 9 hard fescues and 5 strong creeping fine fescue varieties had seedheads on 25% of plots or less:  Predator, SPM, A0163Rel, C-SMX, Pick HF#2, Berkshire, DLF-RCM, IS-FRR30, IS-FL 28, SR 3000, Oxford, DP 77-9360, DP 77-9579, and Heron.  When not treated with glyphosate, the following 12 chewings fescues, 2 strong creeping fescues, and 1 slender creeping fescue had seedheads on 70% or more of plot area:  7 Seas, ACF 174, Jamestown 5, ACF 188, LongFellow II, IS-FRC17, BUR 4601, SRX 51G, SRX 55R, Ambassador, DP 77-9885, DP 77-9886, PST-4TZ, Musica, and Navigator.  When treated with 0.6 kg ai/ha glyphosate, seedhead coverage was less than 6% regardless of variety and seedheads were not produced by any variety when treated with the two higher glyphosate rates.  These data suggest chewings fescues produce the most seedheads while hard fescues and sheep fescues have better glyphosate tolerance.