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Weed control in corn
(2003)
Corn was seeded May 12 at
18,000 seeds/A into 30-inch rows. Individual plots were 10 x 30 ft and
replicated three times. Herbicide treatments were applied June 2 to V2 to V4
corn. The primary weeds evaluated were green foxtail (Grft), kochia (Kocz),
redroot pigweed (Rrpw), common lambsquarters (Colq), wild buckwheat (Wibw), and
cutleaf nightshade (Clns).
|
|
|
Grft |
Kocz |
Rrpw |
Colq |
Wibw |
Clns |
|
Treatmenta |
Rate |
Jun 18 |
Jul
1 |
Jul 15 |
Jun 18 |
Jul
1 |
Jul 15 |
Jun 18 |
Jul
1 |
Jul 15 |
Jun 18 |
Jul
1 |
Jul 15 |
Jun 18 |
Jul
1 |
Jul 15 |
Jun 18 |
Jul
1 |
|
|
|
———————————————% control
——————————————— |
|
Steadfast |
0.75 oz |
99 |
97 |
88 |
85 |
70 |
47 |
98 |
96 |
86 |
89 |
97 |
89 |
92 |
83 |
77 |
93 |
94 |
|
Steadfast +
Atrazine |
0.75 oz +
0.5 pt |
99 |
92 |
78 |
100 |
100 |
98 |
98 |
93 |
84 |
99 |
100 |
99 |
99 |
97 |
91 |
100 |
100 |
|
Steadfast +
Starane |
0.75 oz +
0.33 pt |
99 |
95 |
90 |
96 |
94 |
81 |
97 |
95 |
88 |
90 |
95 |
87 |
94 |
96 |
89 |
95 |
94 |
|
Steadfast +
Starane |
0.75 oz +
0.67 pt |
99 |
95 |
90 |
95 |
96 |
87 |
98 |
94 |
88 |
92 |
98 |
95 |
95 |
94 |
87 |
93 |
94 |
|
Steadfast +
Atrazine+
Starane |
0.75 oz +
0.5 pt +
0.33 pt |
99 |
96 |
90 |
98 |
98 |
92 |
99 |
97 |
90 |
99 |
98 |
95 |
100 |
99 |
97 |
100 |
99 |
|
Steadfast +
Atrazine +
Starane |
0.75 oz +
0.5 pt +
0.67 pt |
99 |
97 |
85 |
100 |
98 |
94 |
99 |
95 |
90 |
100 |
99 |
95 |
99 |
98 |
94 |
100 |
100 |
|
Option +
Starane |
1.5 oz +
0.67 pt |
98 |
96 |
87 |
95 |
95 |
83 |
96 |
90 |
83 |
91 |
98 |
94 |
94 |
92 |
85 |
97 |
100 |
|
Option +
Clarity |
1.5 oz +
2 fl oz |
97 |
95 |
85 |
95 |
93 |
83 |
99 |
95 |
84 |
91 |
99 |
98 |
80 |
73 |
60 |
96 |
98 |
|
Steadfast +
Clarity |
0.75 oz +
2 fl oz |
99 |
97 |
89 |
94 |
88 |
68 |
98 |
95 |
88 |
91 |
100 |
95 |
94 |
88 |
83 |
90 |
92 |
|
Steadfast +
Clarity +
Atrazine |
0.75 oz +
2 fl oz +
0.5 pt |
99 |
95 |
88 |
100 |
99 |
96 |
99 |
95 |
87 |
100 |
99 |
100 |
99 |
97 |
92 |
98 |
99 |
|
Option +
Clarity +
Atrazine |
1.5 oz +
2 fl oz +
0.5 pt |
95 |
93 |
84 |
99 |
98 |
98 |
98 |
94 |
86 |
100 |
100 |
96 |
100 |
96 |
93 |
100 |
100 |
|
Untreated |
|
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
LSD (0.05) |
|
3 |
4 |
5 |
3 |
8 |
17 |
3 |
5 |
8 |
2 |
3 |
7 |
3 |
11 |
17 |
10 |
10 |
|
CV |
|
2 |
3 |
4 |
2 |
6 |
13 |
2 |
4 |
6 |
1 |
2 |
5 |
2 |
8 |
13 |
7 |
7 |
aSteadfast
treatments were applied with MSO and 28% N at 1% v/v & 2 qt, respectively;
Option treatments were applied with MSO and 28% N at 1.5 pt & 2 qt,
respectively.
None of the treatments
caused visible corn injury. We applied the treatments early to control the
heavy population of 2- to 3-leaf foxtail. In the June 18 evaluation (16 DAT),
all treatments provided excellent control of all weeds, with the exception of
Steadfast alone on kochia and lambsquarters, as well as Option + Clarity on wild
buckwheat. Treatments containing atrazine had better season-long control of
several weeds. Lack of soil residual activity in several treatments resulted in
unacceptable weed control later in the season, particularly with kochia.
Steadfast alone provided poor kochia control, likely due to the presence of ALS-resistant
plants.
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