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Integrated Pest & Crop Management



AUTHOR

Kevin Bradley
University of Missouri
Division of Plant Sciences
(573) 882-4039
bradleyke@missouri.edu

Replant Options Following Preemergence Corn Herbicides

Kevin Bradley
University of Missouri
(573) 882-4039
bradleyke@missouri.edu

Published: May 19, 2009

Some of the corn acreage in Missouri has suffered from heavy rains or flooding, and in some of these fields preemergence corn herbicides had already been applied. Yet again this year, questions have arisen about the replant restrictions of preemergence corn herbicides, as some producers now wish to plant soybeans into fields that already had corn and preemergence corn herbicides applied. Table 1 provides a list of some of our most common preemergence corn herbicides and the replant restrictions of these herbicides for corn, grain sorghum, and soybeans. As you can see from this table, soybeans SHOULD NOT be planted into fields where applications of atrazine or an atrazine premix have already been made this season. The label clearly states that soybeans should not be planted until the following year due to the likelihood of soybean injury from residues of atrazine that may still be present in the soil. The average field half-life of atrazine will vary dramatically depending on the soil and environmental conditions experienced, but the Herbicide Handbook published by the Weed Science Society of America lists the average field half-life of atrazine as 60 days. High soil pH's (>7.5) will also slow the degradation of atrazine, along with cool soil conditions. Fortunately, replanting corn or planting grain sorghum into these damaged areas will still be an option where atrazine or most of these atrazine premixes have been applied.

Table 1. Replanting restrictions for some common preemergence corn herbicides
  Interval Between Application and Planting
  Rate V1-V2 Corn at Application V4-V5 Corn at Application
––––––––––––––––––––––––––––––––– Months ––––––––––––––––––––––––––––––
Atrazine 0 0 NYa
Balance Pro 0 6 6
Balance FLexx 0 6 6
Basis 0 10 0.5-10d
Bicep II Magnum 0 0b NYa
Callisto 0 10 10
Camix 0 NYa NYa
Cinch 0 0b 0
Cinch ATZ 0 0b NYa
Define 0 12 0
Degree 0 NYa NYa
Degree Xtra 0 NYa NYa
Dual II Magnum 0 0b 0
Epic 0 12 6
Expert 0 0b NYa
Frontier 0 0b 0
Guardsman Max 0 0b NYa
Harness 0 NYa NYa
Harness Xtra 0 NYa NYa
Hornet 0 12 10.5
Keystone 0 NYa NYa
Lexar 0 NYa NYa
Linex/Lorox 0c 0c 0c
Lumax 0 NYa NYa
Marksman 0 0 NYa
Outlook 0 0b 0
Princep 0 NYa NYa
Python 0 12 0
Radius 0 12 6
Require Q 0 10 10
Resolve/Resolve Q 0 10 10
SureStart 0 NYa NYa
* Indicates control of the initial corn stand 60 days after planting.
a-NY=next year.
b-Replant interval only applies if safener-treated seed is used.
c-Thoroughly rework soil before replanting.
d-Iff 1/3 oz. Basis applied, rotation interval is 15 days. If >1/3 oz. Basis applied, rotation interval is 10 months.
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REVISED: March 6, 2012