Proceedings of the Sixty-first Annual Meeting of the Northeastern ...

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YELLOW NUTSEDGE CONTROL WITH SULFENTRAZONE, SULFOSULFURON AND
MESOTRIONE. P.H. Dernoeden, J. Fu, and S.J. McDonald, Univ. Maryland, College
Park.
ABSTRACT
Yellow nutsedge (Cyperus esculentus, CYPES) is a common problematic weed in
turfgrasses. Three field studies were conducted in 2005 and 2006. Study I involved a
single application of six rates of sulfosulfuron (0.012, 0.024, 0.036, 0.047, 0.059 and
0.070 lb ai/A) and halosulfuron (0.06 lb ai/A) on 17 August 2005. Study II was a
preemergence study in which mesotrione was applied once or sequentially (0.25 and
0.125 + 0.125 lb ai/A) and sulfosulfuron (0.05 lb ai/A) was applied only once beginning on
21 April 2006. Study III compared the effectiveness of single and sequential
postemergence applications of sulfentrazone (0.125, 0.250, 0.375 and 0.125 + 0.125,
0.250 + 0.250, 0.375 + 0.375 lb ai/A); mesotrione (0.250 and 0.125 + 0.125 lb ai/A); and
sulfosulfuron (0.05 lb ai/A) beginning on 26 May and the sequential treatments were
applied 16 June 2006. In Studies I and III, plots were 5 ft by 5 ft and were arranged in a
randomized complete block with four replications. In Study II, plots were 5 ft by 10 ft with
two replicates. Herbicides were applied in 50 GPA using a CO 2 pressurized (35 psi)
sprayer equipped with an 8004E flat fan nozzle. Postemergence treatments were applied
to 2.5-3.0 inch tall CYPES plants. Injury and weed cover data were subjected to
analyses of variance and significantly different means were separated using Fisher’s least
significant difference test at P ≤ 0.05. Mesotrione and sulfosulfuron, but not
sulfentrazone, were tank-mixed with a non-ionic surfactant at 0.25% v/v. In Study I,
sulfosulfuron treatments were applied 17 August and all treatments provided an equal
level of burndown or browning of CYPES leaves by 13 Sep. 2005. Numerous plants
treated at the lower two rates had some green leaf tissue and may have recovered. The
plots were not monitored thereafter and potential recovery of CYPES plants from tubers
was not determined. In Study II and III, the site was treated with glyphosate in early April
and diskseeded with perennial ryegrass (Lolium perenne) on 19 April 2006. In Study II,
treatments were applied preemergence on 21 April and the sequential mesotrione
treatment was applied 18 May 2006. CYPES began to emerge from tubers on 24 April.
Mesotrione did not affect perennial ryegrass emergence or vigor, but sulfosulfuron
reduced germination and seedlings vigor in May. Perennial ryegrass cover, however,
was equal among herbicide-treated plots by 13 July (78 to 88%), which was statistically
greater than was observed in untreated plots (55%). Sulfosulfuron and mesotrionetreated
plots (0.25 lb ai/A) had 11 to 16% CYPES cover, while mesotrione (0.125 + 0.125
lb ai/A)-treated plots had 2% CYPES cover on 13 July. Plots were evaluated for CYPES
recovery from tubers on 15 September. CYPES in sulfosulfuron-treated plots had
recovered (34% CYPES cover) and levels were statistically equivalent to untreated plots
(45% CYPES cover). Mesotrione (0.125 + 0.125 lb ai/A)-treated plots had only 4%
CYPES cover on 15 Sep. In Study III, sulfentrazone (0.375 lb ai/A, and all sequentials)
had provided excellent CYPES control (0 to1% CYPES cover); mesotrione provided fair
control (8 to 13% CYPES cover), and sulfosulfuron (39% CYPES cover) provided no
control, when compared to untreated plots (32% CYPES cover) on 15 Sep. 2006.
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