Maximum Corn & Weed Size For Delayed Herbicide Applications

Source: Penn State University

Table 2.2-10 (from The Penn State Agronomy Guide) Maximum corn size, weed sizes for delayed preemergence/early postemergence herbicide applications.

See specific herbicide label(s) for additional information on application. This type of application generally is used when weather conditions preclude the use of a standard pre­emergence program. For most products, do not apply in liquid fertilizer if com has emerged. Poor control from residual herbicides may result if annual grasses such as foxtail and panicum have emerged at the time of application; tank-mix with product that controls emerged grasses. Delayed preemergence/early postemergence programs can work well with herbicide-resistant corn hybrids now available (e.g., Roundup Ready and Libertylink). When tank-mixing with other pesticides, follow the most restrictive product label.

Maximum Corn and Weed Sizes

Trade Name Maximum Corn Size Maximum Weed Size
Acuron 12 inches 3-inch broadleaves; inconsistent on emerged grasses
Acuron Flexi 30 inches 3-inch broadleaves
Anthem Maxx, Anthem ATZ 4 collars (V4) 2-inch broadleaves, before grass emergence
Atrazine 12 inches 1.5 inches
Axiom before emergence before emergence
Balance Flexx 2-leaf (V2) 1 true leaf stage
Bicep II Magnum 4-leaf or 2 collars 1- to 2-leaf
Corvus 2-leaf (V2) <2 inches (in general)
Dual 5 inches 2-leaf
Dual II Magnum, Bicep II Magnum, Bicep Lite II Magnum, Cinch ATZ Lite 5 inches 2-leaf
Fierce before emergence 2-inch broadleaves; by tank-mix partner for grasses
Guardsman Max/G-Max Lite 12 inches 1.5 inches broadleaves; before grass emergence
Halex GT 30 inches 4 inches
Harness, Harness MAX, Harness Xtra1, or Degree Xtra 11 inches or by tank-mix partner before broadleaf emergence, 2-leaf grasses or by tank-mix partner
Instigate 2-leaf (V2) 3 inches
Lexar EZ 12 inches 3-inch broadleaves; before grass emergence
Lumax EZ 12 inches 3-inch broadleaves; inconsistent on emerged grasses
Outlook 12 inches before emergence or by tank-mix partner
Prequel before emergence before emergence
Princep before emergence before emergence
Prowl H2O 30 inches before weed emergence
Python WDG/Accolade 20 inches (V6) before weed emergence
Resicore 11 inches 3-inch broadleaves
Resolve 12 inches 2-inch grasses; 3-inch broadleaves (in general)
SureStart II/TripleFLEX II11 inches 11 inches limited activity on 1-inch broadleaves; before grass emergence
Surpass NXT, FulTime NXT, TopNotch, or Keystone NXT, Breakfree NXT ATZ2 11 inches or by tank-mix partner before emergence or by tank-mix partner
Verdict before emergence before emergence
Zemax 30 inches (8-leaf) 3-inch broadleaves; before grass emergence
Zidua early postemergence before emergence or by tank-mix partner

1May be tank-mixed with Accent, atrazine (Harness), Banvel or Clarity, Marksman, Permit, or Roundup (Roundup Ready corn).
2May be tank-mixed with a number of different products, including Accent Q, Banvel or Clarity, Prowl, etc. See an herbicide label for specific information.

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