Vol. 51—1997 - NorthEastern Weed Science Society

67
EV ALUATIO OF WIT..DFLOWER ESTABLISHMENT IN TURFGRASSES SUPPRESSED
WI1H HERBICIDES
Chad W. Spackman, Jon M. Johnson, and Larry J. Kuhnsl/
ABSTRACT
As part of a tive research project between the Pennsylvania Department of
Transportation an the Pennsylvania Department of Transportation, a study was conducted in 1995
in which annual owers were established in tall fescue (FestucaarundinaceaSchreb.) suppressed
with herbicides. e objective was to establish flowers in a suppressed turf that could be mowed
in the fall, leavin a stand of established turf. A similar study was established in 1996.
Treatments inclu ed an untreated check; glyphosate at 0.25,0.50,0.75, and 4lbs/ac; ethephon-' at
8 lbs/ac; trinexap c-ethyl at 0.375 and 0.75 lbs/ac; ethephon plus trinexapac-ethyl at 8 and 0.375
lbs/ac, respective y; and imazameth at 0.032Ibs/ac plus 0.125% (v/v) QwikWet 357. All
treatments con . ed Polytex Al001 drift control at 0.25% (v/v). The study area was arranged in a
randomized com lete block design with threereplications. Treatments were applied to 6 by 10 ft
plots in an unmo edt mixed stand of tall fescue and Kentucky bluegrass (PoapratensisL.) on
May 3, 1996. usi g a CO2-powered sprayer equipped with Spraying Systems XR 8004 VS spray
tips. delivering GPA at 35 psi. On May 10, 7 days after treatment (DAT). the untreated check
was mowed to 1. 5 in and clippings removed; the entire study area was verticut two times to a
depth of 0.5 in an excess thatch was removed; plots treated with glyphosate at 4 lbs/acwere
rototilled to sim ate a conventional seeding method; and all plots were seeded with annual flowers
at 12Ibs/ac. The annual flower mix contained 68% cosmos (CosmosbipinnatusCav.), 21.5%
cornflower (Cent ea cyanusL.). and 10.5% tall plains coreopsis (CoreopsistinctoriaNutt.),
The study area w s mowed September 25. Turf green cover ratings were taken May 3; May 10;
June 4.32 OAT; uly 25,83 OAT; and October 10,160 OAT. Average canopy height of the turf
was measured at ach rating period. A ground cover rating of weed pressure in each plot was
taken September O.130 OAT. Ratings of ground cover and average heights of the flowers were
taken July 25 an September 10. Results of turf ratings are reported in Table la and flower ratings
in Table lb.
Plots initially howed no differences in the amount of desirable turf and contained little weed
pressure. No was present throughout the study in the plots treated with 4 lbs glyphosate and
rototilled. The wed check, ethephon alone, and both trinexapac treatments alone. provided
significantly mo green cover on June 4 than all other treatments. Only the 0.751b rate of
glyphosate siani tly reduced the turf cover compared to the mowed check in July and October.
Glyphosate seve ly injured the bluegrass but only suppressed the tall fescue. No differences in
turf height were bserved at any rating period. with initial heights of 5 in and final heights of 14 in.
There was a signi cant difference in the weed pressure at the end of the study, with glyphosate at
0.75 lb plots ha . g 50 percent cover. Glyphosate treated plots at 0.5 and 4lbs, also had
significantly mor weeds thanthe mowed check and plant growth regulator treatments.
Glyphosate trea plots provided significantly higher wildflower cover than other treatments at
both rating peri s, At the September rating, glyphosate at 4 lbs provided the tallest wildflowers
with an average 50 in, and the other glyphosate plots had heights from 31 to 39 inches. The
mowed check av ge height was 20 in. All threespecies germinated in all plots.
Glyphosate a 4 lbs/ac plus rototilling resulted in increased wildflower cover and height,
however no desir ble turf remained Glyphosate at 0.75 lbs/ac resulted in increased wildflower
cover and height ut thinned the turf and had the highest percentage weed cover at the end of the
study. Glyphosa at 0.5 lb/ac provided an acceptable stand of wildflowers anddesirable turf.
The mowed chec and plant growth regulator treatments had no reduction in turf and little weed
invasion, but had poor stands of wildflowers.
1/ Research Technol gist. Project Assistant. and Professor of Ornamental Horticulture, respectively, The
Pennsylvania S University, University Park, PA.
2/ Ethrel, 4 lbs ethe on/gal, Rhone-Poulenc, is not currently labeled for use on turf.