“New” Corn Herbicides for 2008

Russ Hahn, Department of Crop & Soil Sciences, Cornell University

NY field corn producers should be aware of several “new” herbicides they may want to consider for the 2008 growing season and beyond:

Impact from AMVAC is registered for use on both field and sweet corn. Corn growers are likely familiar with another herbicide, Callisto, with the same site-of-action. While Callisto can be used both preemergence and postemergence (POST), Impact is for POST use only from the spike stage of corn up to 45 days prior to harvest. Impact has excellent activity against many annual broadleaf weeds including velvetleaf, pigweed, common ragweed, common lambsquarters, and wild mustard. It also provides significant burndown against annual grasses like giant foxtail and large crabgrass. The normal application rate is 0.75 fl oz/A, and the spray solution must include MSO (methylated seed oil) or COC (crop oil concentrate) and a nitrogen fertilizer source such as UAN (urea ammonium nitrate) or AMS (ammonium sulfate). For best performance, Impact should be tank mixed with 0.25 to 1 lb ai/A of atrazine. Small grains can be planted 3 months after application while alfalfa, soybeans, and several other crops can be planted after 9 months. The rotational interval for many other crops is 18 months.

Status from BASF is registered for field corn but not sweet corn. Dicamba, one of the active ingredients in Status, is also the active ingredient in Banvel and Clarity. Each of these products has activity against a wide variety of broadleaf weeds. Dicamba is rapidly absorbed by foliage and roots and readily moved throughout plants. It accumulates in growing points causing uncontrolled growth and plant death. A second active ingredient in Status, diflufenzopyr, blocks movement of dicamba away from growing points and increases the activity of the dicamba. Status also includes a safener for dicamba on corn. This safener should minimize concerns about the types of adjuvants and tank-mix partners used with Status. Status can be applied to field corn from 4 to 36 inches tall at rates of 5 to 10 oz/A. Adjuvants must be used with Status. Best results are achieved by combining a NIS (non-ionic surfactant), MSO, or COC with UAN or AMS. If at least 1 inch of rainfall is received following application of 5 oz/A or less, alfalfa, small grains, and soybeans can be planted 30 days after the rainfall event. Results from comparisons we’ve made in NYU suggest that Status may not consistently provide better weed control than Banvel or Clarity. In addition, Status is more costly than Banvel or Clarity and requires the use of spray additives. Unless corn injury is a concern, growers should proceed with caution until additional research is completed with Status.

Halex GT from Syngenta combines residual herbicides with glyphosate in a single product for use in glyphosate-resistant corn. This new product, which is available in bulk only, combines glyphosate for control of emerged weeds with Dual Magnum and Callisto for residual annual grass and broadleaf control. In addition to providing residual activity against a broad spectrum of weeds, this premix provides three different site-of-action (ways of killing weeds) classifications. The label shows that Halex GT contains herbicides from Groups 15 (Dual Magnum), 9 (glyphosate), and 27 (Callisto). With multiple sites-of-action, this product simplifies efforts to prevent development of herbicide-resistant weed populations. The label allows for the addition of atrazine with a fourth site-of-action (Group 5). In fact, Halex GT use guidelines encourage the addition of atrazine if broadleaf weeds are greater than 4 inches tall. Halex GT should be applied at 3.6 to 4 pt/A from corn emergence up to 30 inches in height and should be applied with NIS and AMS. Small grains may be planted after 4 months, and alfalfa and soybeans after 10 months.