Weed Control Guide for Ohio Field Crops

Corn Herbicide Management Strategies

Preemergence herbicide programs have long been the mainstay of weed management in corn, due in large part to the low cost of atrazine and its broad spectrum of control. A total preemergence approach can still be effective in fields with low to moderate populations of most annual weeds. The commonly used premix of atrazine plus an acetamide herbicide (Bicep II Magnum, Degree Xtra, Fultime, etc) can be supplemented as necessary with Balance, Python, Hornet, or simazine to improve control of weeds such as fall panicum, triazine-resistant lambsquarters, and velvetleaf. However, all of these tank-mix partners except simazine can occaionally injure corn, especially when corn is planted too shallow, on coarse-textured soils, and when cold, wet conditions occur after planting. In fields with moderate to high weed populations, a preemergence plus postemergence approach will provide more consistent control with less risk of corn injury. A number of options are available for this type of program at a reasonable cost. A preemergence plus postemergence approach is especially effective in fields with giant ragweed, burcucumber, moderate to high annual populations of anual grass, velvetleaf, and triazine-resistant lambsquarters, and perennial weeds. A number of effective total postemergence herbicide programs are also available. However, OSU research indicates that total postemergence programs that lack residual activity should be used only in fields with low weed populations. A total postemergence herbicide program should be applied before most weeds in a field exceed 4 to 6 inches in height, and reinfestation with later-emerging weeds is likely if a herbicide with residual activity is not included. Using a postemergence program that has substantial residual activity allows more flexibility in the window of application. Herbicides can be applied when weeds are anywhere from 2 to 5 inches tall, since the residual component will control weeds that emerge after application.

Back | Forward | Table of Contents