Weed Control Guide for Ohio Field Crops

Total Postemergence Corn Herbicide Programs (with residual)

Total postemergence (POST) herbicide programs that provide substantial residual control can be used in fields with:

• most annual weed populations

Avoid use in fields with:

• perennial broadleaf weeds (might emerge too late for control)
• high giant ragweed and annual grass populations

Advantages of total POST with residual:

• one-pass, can plant first and apply later
• not dependent upon rainfall for postemergence activity (although soil moisture status affects weed response to herbicides)
• consistent control of many annual weed populations

Disadvantages of total POST with residual:

• should be applied before weeds exceed 4 inches in height to avoid yield loss
• application too early for best perennial weed control
• need rain within 2 weeks of application for residual activity

Approaches:
Can make a single postemergence application before weeds exceed 4 inches in height with mix of postemergence herbicides with grass and broadleaf activity and residual herbicides with primarily broadleaf activity (if grass population not high). Examples:

• Liberty ATZ (Liberty Link corn)
• ReadyMaster ATZ (RR corn)
• Accent + Marksman

In fields with moderate to high grass pressure, may need residual component with more activity on grasses than those listed above. Examples:

• Glyphosate + Harness Xtra (RR corn)
• Lightning + atrazine (Clearfield corn)

The following examples have limited soil residual, but residual may not be broad-spectrum or long enough in fields with moderate to high weed populations:

• Accent Gold
• Basis Gold + Clarity

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