Vol. 51—1997 - NorthEastern Weed Science Society

44
EXTE DED EFFECTIVENESSOF POSTEMERGENCECRABGRASSCONTROL
S. Wayne Bingham and Lloyd Hipkins!
ABSTRACT
dulum Post and Preclaim are similar mixtures of fenoxaprop and
pendime alin. These formulations were not directly compared to each other since they
are essen .ally the same; however, they were compared to fenoxaprop as Acclaim and
Acclaim tra and in some cases to a few preemergence herbicides. The more active
fenoxapr p isomer in Acclaim Extra is also in Pendulum Post and Preclaim.
In 995, Pendulum Post provided excellent crabgrass control for 10 weeks as
compare to Acclaim Extra for less than 6 weeks. Bluegrass quality also remained good
until era ass control became poor at 15 weeks. With the temporary injury occurring
with Acc im Extra, bluegrass quality was below acceptable and in open or thin
turfgrass crabgrass occurred at 6 weeks. Similar injury occurred with Pendulum Post;
however, pendimethalin reduced further emergence of crabgrass in the thin bluegrass,
Dithiopy gave 90% crabgrass control (1 to 3 tiller stage) and was similar to Acclaim
Extra aft r 3 weeks in regard to crabgrass control and turfgrass quality.
D ring 1996, pendimethalin and dithiopyr applied preemergence gave excellent
crabgras control for 16 weeks. Pendulum Post applied on 4 leaf crabgrass was equally
effective uring this period. Acclaim Extra gave excellent crabgrass control for 4 weeks
and allo ed reoccurrence before 9 weeks. Bluegrass injury was slightly less when
fenoxapr p was applied later in the season. Bluegrass quality was acceptable during
the entir period with pendimethalin and dithiopyr applied preemergence; however,
quality 0 bluegrass was slightly more variable with Pendulum Post.
P laim provided excellent crabgrass control for 14 weeks and did not appear
influenc d by triclopyr alone. However, broadleaf herbicides (triclopyr + clopyralid
and 2,4- + mecoprop + dicamba) reduced the effectiveness of Preclaim for crabgrass
control ter 8 weeks. Tank mixtures of Acclaim Extra with 2,4-D + mecoprop +
dicamba also showed a similar response on crabgrass.
inclorac at 0.75 lb aij A provided excellent crabgrass control but 0.50lb aiJ A
ffective at 4 weeks.
lProfess r Emeritus and Senior Research Associate, Department of Plant Pathology,
Physiol gy and Weed Science, Virginia Tech, Blacksburg, VA 24061-0331