NEW
FEATURE ARTICLE
HERBICIDES FOR 2021, PART I
By Scott McElroy, Ph.D. – Professor, Department of Crop, Soil, and Environmental Sciences Jim Harris – Research Associate, Department of Crop, Soil, and Environmental Sciences, Auburn University The following article will discuss select new products that will be available for turfgrass industry use in 2021. The discussion of these products is not an endorsement of the products and exclusion of products that may be newly available is not opposition to those products. Products discussed have been researched in Dr. McElroy’s research group and some available data is presented. Always follow the label regardless of what any article may say about a product. The label is the law.
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ew herbicide products do not necessarily mean new active ingredients. New herbicide product names may simply be repackaged active ingredients or novel mixtures of previously available active ingredients. Novel active ingredients are a rarity with respect to new herbicide products. The lack of a novel active ingredient does not necessarily mean that the products do not bring a new control angle to the turfgrass industry. Novel combinations of older active ingredients can provide additive or even synergistic herbicide effects and can broaden the spectrum of weeds controlled. But with new combinations it is important to understand the activity of individual active ingredients contained in the products.
Coastal Coastal herbicide is a new combination of older products – imazaquin, prodiamine, and simazine. Imazaquin previously labeled as Image can now be purchased as the stand alone product Scepter T&O. Prodiamine was first labeled as Barricade and simazine was first labeled as Princep (There are other product names, it is simply easier to refer to the first product name used). New herbicide mixtures primarily target new combinations of post herbicides — Trimec-type herbicides or herbicides with mixtures of sulfentrazone (Dismiss) and quinclorac (Drive). Echelon is a combination of prodiamine and sulfentrazone, pre and post, respectively, but few (if any) others exist. Coastal is another unique combination because it also combines both pre and post herbicides. Prodiamine is strictly a preemergence herbicide with no postemergence activity. Simazine is used for post winter weed control, primarily Poa annua, but it can provide 14–28 days of residual. Imazaquin is a postemergence herbicide with minimal residual activity. Coastal is labeled for use on bermudagrass, centipedegrass, St. Augustinegrass, and zoysiagrass. Like the name implies, it is primarily targeted at warm-season turf along the gulf coast. Being registered for weed control on the four-primary warmseason grasses is important for lawn care because it does not require the changing of products from one turfgrass lawn to the next.
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MTC TURF NEWS
Research conducted in 2019–2020 evaluated Coastal in September and October for Poa annua and winter annual broadleaf control. Coastal was applied at 32 or 64 fl oz/a with or without metsulfuron (MSM) at 0.5 oz/a. A comparison treatment Specticle at 6.5 fl oz/a plus metsulfuron at 0.5 fl oz/a was included. •A ll treatments controlled Poa annua completely regardless of split or single applications (data not shown). The additional benefit of Coastal is that it also provided effective control of the annual broadleaf, small hop clover (Trifolium dubium; Figure 1). Coastal with and without metsulfuron reduced hop clover cover to 2–4%, while hop clover cover was > 25% in non-treated plots. The combination of residual activity from prodiamine and simazine combined with the postemergence activity of simazine and imazaquin likely lead to the effective control.
FIGURE 1: Small hop clover control with Coastal.
