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Effectiveness
of Some Newer Herbicides on Selected Broadleaf Perennial Weeds
in Corn. T.
J. Fritz, W.S. Curran, and N. L. Hartwig, 1992. Proc. NEWSS 46:30-31.
Perennial weeds in corn seem to be
increasing in Pennsylvania. Nicosulfuron, primisulfuron, clopyralid,
and dicamba were evaluated on horsenettle (Solanum carolinense
L.), and Canada thistle (Cirsium arvense L.) during the
1991 growing season. In addition, the efficacy of these materials
excluding clopyralid were also evaluated in 1990 and 1991 on dewberry
(Rubus sp.).
Extension agents in Erie, Montgomery
and York counties located fields with moderate horsenettle infestations
and conducted identical trials. Each location was a randomized
complete block design with 4 replications. Identical treatments
were applied postemergence at a early and late timing. Rates applied
(lb/A) were as follows: nicosulfuron, 0.031 and 0.062; primisulfuron,
0.036 and 0.071; clopyralid, 0.125 and 0.25; and dicamba, 0.25
and 0.5, respectively. The York County results were poor due to
drought and insect damage. Erie and Montgomery County results
were more similar to one another. Primisulfuron and dicamba provided
the best control, while nicosulfuron and clopyralid did not show
much activity. Optimum application timing could not be determined
by these trials. Late applications performed better at Erie, while
the early applications performed better at Montgomery. Higher
rates generally performed better than lower rates, although not
consistently.
A postemergence
randomized complete block design with 3 replications was used
to evaluate control of Canada thistle. Clopyralid (0.094 and 0.25
lb/A) was applied at an early and late timing at both rates. Dicamba
was applied at the high rate (0.5 lb/A) during the early application
and at the low rate (0.25 lb/A) during the late application timing.
Nicosulfuron (0.031 lb/A) and primisulfuron (0.036 lb/A) were
applied during the late timing. Trends were as follows: clopyralid
applied during the late application performed the best, dicamba
applied at the high rate early performed better than the low rate
applied later, primisulfuron was fair, and nicosulfuron was poor.
A randomized
complete block design with 3 replications was used to evaluate
control of dewberry in 1990 and 1991. Postemergence treatments
of nicosulfuron (0.031 and 0.047 lb/A), atrazine (2.0 lb/A), dicamba
(0.25 lb/A), and primisulfuron (0.036 and 0.054 lb/A) were applied.
None of the herbicides were very effective the year of application.
In the second year evaluation of the 1990 application year, nicosulfuron
provided excellent control, while atrazine control was fair. Control
of dewberry was poor for dicamba and primisulfuron.
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