Vol. 51—1997 - NorthEastern Weed Science Society

7
TaL~NCEaFHNE~CU~TaCL~HarnM
Larry J. Kuhns And Tracey L. Harpster'
ABSTRACT
In past studies it was found that fine fescues were immune to the effects of two of the most
commonly used graminicides, fluazifop-p-butyl and sethoxydim. This study was initiated to
determine the tolerance of three fine fescues; chewings (Festucarubra spp. commutata Gaud.­
Beaup.), hard (FestucalongifoliaThuill.), and creeping red (Festucarubra L.); to clethodim alone
or with a crop oil concentrate (CDC) or a non-ionic surfactant (NIS)2. The treatments presented in
Table 1 were applied on October 23, 1995. The percent green cover was rated on May 22 and
July 9, 1996. Thq treatments presented in Table 2 were applied on May 31, 1996 and were
evaluated on July 9, 1996. All treatments were applied with a CC>:2pressurized test plot sprayer at
30 psi through an ~E nozzle at 22 GPA. A randomized complete block design with three
replications per treatment and species was used.
Applied inlthe fall at O.25lb/a alone or with NIS, clethodim had little effect on chewings or
creeping red fescue (Table 1). With hard fescue, some injury was evident on May 22, but it
recovered by July p. The addition of cac resulted in moderate injury to all three species, with
only partial recovery by July 9. Severe injury of all species from clethodim applied at l lb/a was
evident on May 24' The amount of recovery that occurred by July 9 was dependent on the spray
additive used. With none, all of the grasses recovered fairly well. With NIS, moderate injury to
hard fescue persisted:and with COC, unacceptable injury to all species persisted.
Similar results were obtained when the treatments were applied in the spring (Table 2).
The 0.251b/a rate caused slight injury, regardless of additive. The 1.0 Ib/a rate caused severe
injury, with treatments including cae injuring hard fescue slightly worse than those including
NIS. The 0.5lb/a'rate caused an intermediate degree of injury.
None of the clethodim treatments totally killed any of the fine fescues. However,
unacceptable injury was caused by the 0.5 and 1.0 lbla rates, regardless of additive, and by the
0.251bla + cac treatment. Injured turf was invaded by broadleaved weeds and was lower quality
even after recovering from initial injury.
1 Prof. of Ornamental Horticulture and Research Associate, Dept. of Horticulture, The Pennsylvania State
University, University Park, PA 16802
2 X-77 Spreader, Loveland Ind., Inc.•Greeley, CO 80632-1289