Weed Control Guide for Ohio Field Crops

Preemergence Corn Herbicide Programs

Total preemergence (PRE) herbicide programs fit fields with:

• low to moderate annual grass populations
• low giant ragweed populations
• any population of most annual broadleaf weeds

Total preemergence programs do not fit fields with:

• high grass populations
• moderate to high giant ragweed, cocklebur, velvetleaf, and annual morningglory populations
• perennial weeds
• burcucumber

Advantages of PRE programs:

• one-pass, can apply while planting
• with adequate rain, provides control through the first 6 weeks, and later-emerging weeds have much reduced impact on corn yield
• effective on many annual grass and broadleaf weeds

Disadvantages of PRE programs:

• dependence upon adequate rain within narrow period of time
• not effective enough on tough broadleaf or perennial weeds or in high grass populations
• corn needs to be competitive earlier in season compared to PRE plus POST programs

Approaches:
Atrazine premix products (Bicep, Harness Xtra, etc) or similar mixes are effective broad-spectrum treatments for fields suited to total preemergence.

• can add simazine or Balance to improve grass control
• can add reduced rate of Balance to boost consistency under low rainfall conditions
• can add Balance, Callisto, Python, or Hornet to improve triazine-resistant lambsquarters and velvetleaf control
• atrazine rates of 1.5 to 2 lb/A can improve control of velvetleaf and giant ragweed some premix products have less than 1.5 lbs/A

In low to moderate grass populations with adequate rain, it is difficult to tell difference between grass herbicides, especially when mixed with atrazine. However, differences show occasionally in OSU research:

For longevity of grass control:

Axiom = Degree = Dual II Magnum > TopNotch > Harness = Outlook > Balance
(TopNotch similar to Dual II in no-till, but similar to Harness in tilled fields)

Amount of rain needed for activity:

Balance < Harness = TopNotch < Outlook = Degree < Axiom = Dual II Magnum

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