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Weeds Waking Up: Cocklebur

March 29, 2019

Knowing when weeds emerge can help distinguish between weeds that may have similar characteristics in their early growing stages. For cocklebur, the next weed in our Weeds Waking Up series, the seedling stage can often be confused with giant ragweed, as the long fleshy cotyledons of cocklebur look similar. However, giant ragweed emerges several weeks prior to corn and soybean planting over a short duration of about 2 to 3 weeks, while cocklebur emerges closer to the end of corn and soybean planting.

Cocklebur has very large leaves that can intercept a lot of sunlight, causing competition with your crop, which will in turn can cause a yield reduction if left to compete with your crop.

Additionally, cocklebur is a prolific seed producer; therefore, it is critical to manage the weed seed bank. If an infestation occurs, the seeds can last up to 35 years in the soil, which can increase management costs for many years to come.

It is crucial to control this weed early in the growing season so it does not get a chance to compete with your crop. Cultural practices to help control this weed include narrow row spacing and increasing plant populations to create more competition with this weed species.

When considering management options for the control of common cocklebur, it’s important that you apply an effective pre-emergence application at planting to maintain control of this weed season long.  Start clean and stay clean throughout the season with an application of Acuron® or Acuron Flexi corn herbicides. Acuron has 3 effective sites of action (Groups 5, 15 and 27) and Acuron Flexi has 2 (Groups 15 and 27). Both herbicides contain bicyclopyrone, which is designed to complement the other active ingredients in the premix to deliver broader spectrum, more consistent control of tough weeds other products are missing.

In soybeans, Syngenta recommends a post-emergence herbicide, such as Flexstar® GT 3.5 that delivers 2 different sites of action (Groups 9 and 14),

If you would like input in developing a herbicide program for 2019 based on the specific weed pressures in your field, contact your Syngenta retailer, local Syngenta sales rep or visit www.ResistanceFighter.com.

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