Also, it is important to change herbicide programs from time to time so that you do not get hooked on any single herbicide program year after year. Thus, it’s important to know the strengths and weaknesses of each product in terms of the spectrum of weeds controlled. A table summarizing weed species response to various corn herbicides can be found on pages 24-26 of 2016 Chemical Weed Control for Field Crops, Pastures, Rangeland, and Noncropland (SRP 1126). See: http://www.ksre.ksu.edu/bookstore/pubs/chemweedguide.pdf
Nitrogen Metabolism Inhibitors (10)
Isoxazole family (27) – Balance, Huskie
ALS-AHAS inhibitors (2):
A new herbicide from Syngenta called Acuron contains Lumax EZ (27, 15, 5) + bicyclopyrone (27). Bicyclopyrone is an HPPD-inhibitor herbicide that enhances large-seeded broadleaf weed control and also has grass activity. Acuron (27, 15, 5) has enhanced control of giant ragweed, common ragweed, common cocklebur, and velvetleaf, along with improved morningglory control over Lumax EZ. An herbicide just registered in 2016 is called Acuron Flexi (27, 15) which is basically Acuron without atrazine. Acuron Flexi (27, 15) and Zemax (27, 15) which is basically Lumax without atrazine (5) were developed for areas where atrazine generally isn’t used or is prohibited. Without the atrazine (5), less broadleaf weed control is expected.
Cyclohexanedione family – Poast, Poast Plus, Select, Volunteer, Section, Arrow, Tapout
N-Phenylphthalimide family (14) – Encompass, Resource, Valor
Visit Acuron-Herbicide.com or talk to your local Syngenta retailer to learn more.
Cocklebur, giant ragweed and morningglory are often referred to as “large-seeded” broadleaf weeds because they produce larger seeds than their small-seeded counterparts: lambsquarters, marestail and waterhemp. While large-seeded broadleaf weeds tend to produce fewer seeds, the seeds are heartier and often remain viable in the soil for decades. Due to their larger size, the seeds often emerge from deep within the soil profile and present a larger plant mass when they appear, making them more established and difficult to control. To complicate matters, they often appear in flushes, which makes choosing a herbicide with strong residual control a must.
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Since large-seeded broadleaves often come in flushes and residual is important to maintain season-long control, we recommend applying Acuron or Acuron Flexi in a 2-pass system: a foundation rate of Acuron or Acuron Flexi followed later by the remaining rate. This approach incorporates multiple, effective modes of action and helps ensure long-lasting residual control.
The best approach to large-seeded broadleaf weed control in corn is to start clean with a burndown application or a burndown application followed by an application of Acuron® or Acuron Flexi corn herbicide. Both Acuron brands contain multiple, effective modes of actions including bicyclopyrone (group 27), which was developed to complement Callisto® herbicide (group 27) and provides improved control of large-seeded broadleaves.
All photos are either the property of Syngenta or are used with permission.
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Cobra. Cobra controls most annual broadleaf weeds. Major exceptions are lambsquarter, sicklepod, smartweed, and spurred anoda. Morningglory control often is inconsistent. Cobra applied at the full labeled rate (12.5 ounces per acre) usually causes moderate to severe soybean leaf burn. Although the soybeans usually recover and grow normally, the injury often is unacceptable to growers. For this reason, Cobra at the full labeled rate is generally not recommended. Several tank mixes containing Cobra at low rates (6 ounces per acre) are registered.
Pursuit kills weeds very slowly, and it may take as long as 3 weeks to kill morningglory. In some cases, the weeds do not die completely but rather stop growing and the soybean canopy fills in above them. In addition to controlling certain broadleaf weeds, a postemergence application of Pursuit usually gives adequate control of broadleaf signalgrass, foxtails, seedling johnsongrass, and shattercane, and it sometimes gives adequate control of rhizome johnsongrass. Pursuit does not control common ragweed, lambsquarter, prickly sida, sicklepod, and certain other weeds.