Vol. 54—2000 - NorthEastern Weed Science Society

TRINEXAPAC-ETIIYL EFFECTS ON TIIATCH DEVELOPMENT AND MOWING
QUALITY OF 'TIFWAY' BERMUDAGRASS
MJ. Fagemess and F.H. Yelverton'
ABSTRACT
Recent observations of reduced mowing injury in trinexapac-etbyl (TE) treated 'Tifway'
bennudagrass [Cynodon doctylon (L.) Pers. x Cynodon transvoolensis (Burtt-Davy)]
produced the bypothesis that, in addition to canopy height reduction, TE may affect the
developmentof thatchin this species. Researchwas conductedat two locations in North
Carolinain summer1999 to investigatehow variousseasonalapplicationpatternsof TE
affected thatchlayer developmentin established'Tifway' bermudagrassover the course
of the growing season. TE was applied once, twice, or three times during the growing
season at 0.11 kg a.i./ha. Physical development of the thatch layer was quantified through
measurements of thatch depth and thatch biomass while mowing quality was assessed
using subjectivevisual qualitymeasurementsandquantificationof both shootdensityand
the percentage of verdure which was green tissue. Additioual assessment of mowing
quality was achieved through acquisition and comparative analysis of digital images. All
measurements were conducted at biweekly intervals, beginning at the time TE was
initially applied. While thatch development parameters did vIII}' with location, results
showed that neither thatch depth not thatch biomass were appreciably affected by TE at
either location, especially later in the growing season when chmnic effects of TE might
be most evident. However, patterns of visual quality and shoot density did favor areas
treated with TE, illustrating that a) assessment of torfgrass quality is influenced by shoot
density and b) reduced canopy heights in TE treatedareas, coupled with increased shoot
density, may serve to buffer 'Tifway' bennudagrass from mowing injury. Additioually,
measurementsof the percentageof verdurecomposedof greenshoot materialfavoredTE
treated areas, especially earlier in the growing season. This pattern diminished towards
the end of the growing season, as did patterns of TE enhanced shoot density and visual
quality. The absence of dramatic differences among plots inhibited the utility of digital
image analysis for quantifying mowing quality but identified trends showed TE treated
torfto be of higher mowing quality. Overall, results suggested that TE effects on canopy
development in 'Tifway' bennudagrass can have a significant impact on mowing quality
while development of the thatch layer was unaffected by TE and seemed of limited
importanceto mowing quality.
, Research Assistant and Assoc. Prof., Crop Science Dept., North Carolina State
University, Raleigh, NC 27695-7620
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