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

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POSTEMERGENCE ANNUAL GRASS CONTROL IN CORN WITH HPPD
INHIBITORS. R.R. Hahn and P.J. Stachowski, Cornell Univ., Ithaca, NY.
ABSTRACT
Postemergence (POST) activity of mesotrione, tembotrione, and topramezone
was evaluated for giant foxtail (Setaria faberi Herrm.) and large crabgrass (Digitaria
sanguinalis (L.) Scop.) control in corn (Zea mays L.). Previous research showed that
mesotrione has significant POST activity on large crabgrass but little activity on giant
foxtail. POST activity of topramezone on giant foxtail was observed in 2005 near
Aurora, NY. Due to inadequate rainfall, giant foxtail was not controlled with
preemergence (PRE) applications that were to be followed by POST applications of
mesotrione or topramezone. PRE applications of 1.43 lb ai/A of metolachlor controlled
only 60% of the giant foxtail. When PRE metolachlor applications were followed by
POST applications of 0.094 lb ai/A of mesotrione or 0.016 lb ai/A of topramezone in
combinations with 0.5 lb ai/A of atrazine and appropriate adjuvants, these POST
applications controlled 87 and 99% of the giant foxtail respectively. These PRE
followed by POST treatments averaged 130 bu/A of corn compared with 81 and 100
bu/A for the untreated check and PRE metolachlor treatment respectively. An
experiment established in 2006 near Aurora compared POST applications of 0.094 lb/A
of mesotrione, 0.123 lb ai/A of tembotrione, and 0.016 lb/A of topramezone with 0.56 oz
ai/A of a nicosulfuron/rimsulfuron premix. Each of these POST treatments included 0.5
lb/A of atrazine plus appropriate adjuvants. Applications were made when giant foxtail
was 3 inches tall. Tembotrione, topramezone, and nicosulfuron/rimsulfuron treatments
each controlled >95% of the giant foxtail while mesotrione only controlled about 20%.
Other treatments demonstrated the activity of tembotrione and topramezone for giant
foxtail control in POST combinations with 1.43 lb ai/A of pendimethalin plus 1 lb/A of
atrazine. When applied alone, pendimethalin plus atrazine controlled less than 20% of
the giant foxtail. When the pendimethalin plus atrazine combination was tank mixed
with tembotrione or topramezone, giant foxtail control was 99%. An experiment was
also established in 2006 near Valatie, NY in a field with good large crabgrass pressure.
Early postemergence (EPOST) applications were made when corn was in the V2 stage
of development and large crabgrass was less than 0.5 inch tall. When the three HPPD
inhibitor herbicides were applied following PRE application of 0.5X rate of metolachlor,
large crabgrass control 3 and 9 weeks after treatment (WAT) averaged 98 and 90%
respectively. These PRE followed by EPOST treatments produced an average of 120
bu/A of corn. When applied EPOST in combinations with 0.5 lb/A of atrazine and
appropriate adjuvants, large crabgrass control 3 WAT was 97% with 0.094 lb/A of
mesotrione or 0.123 lb/A of tembotrione, while 0.016 lb/A of topramezone controlled
90% of the crabgrass. Control declined to 60% with mesotrione and tembotrione, and
to 45% with topramezone by 9 WAT. Large crabgrass control with 0.56 oz/A of
nicosulfuron/rimsulfuron plus 0.5 lb/A of atrazine was 65% 9 WAT. These EPOST
treatments produced an average of 120 bu/A of corn while the untreated check
produced 80 bu/A.
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