Weed Control Guide for Ohio Field Crops

Preemergence Soybean Herbicide Programs

Total preemergence (PRE) herbicide programs fit fields with:

• low annual grass populations
• low to moderate populations of annual broadleaf weeds, including common ragweed, smartweed, pigweed, and velvetleaf
• most populations of lambsquarters

Total preemergence programs do not fit fields with:

• moderate to high annual grass populations
• giant ragweed, cocklebur, burcucumber, marestail, annual morningglory, waterhemp, or marestail
• perennial weeds

Advantages:

• 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 soybean yields

Disadvantages:

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

Approaches:

The most broad-spectrum programs include mixtures of a grass herbicide (Command, Dual, Outlook, Prowl, etc) with Canopy XL, FirstRate, Gauntlet, or Scepter, or use of premix products such as Steel or Squadron. Python and Sencor have less activity on tough broadleaf weeds compared to the previously listed products. OSU research results suggest the following ranking of preemergence grass herbicides (Axiom not included because rates labeled for soybeans are too low for season-long control):

For longevity of grass control:

Command > Dual II Magnum > Outlook > Prowl = alachlor

Amount of rain needed for activity:

Command < Outlook < Dual II Magnum = alachlor < Prowl

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