Herbicides are designed to injure or kill either a single species of plants or a range of plant species. This fact makes herbicides a powerful asset in the battle to save your plants from invasive weeds and grasses; it also makes herbicides potentially dangerous. Herbicide injury occurs when a plant other than the plant you are trying to kill with the herbicide (the "non-target species") suffers a deleterious reaction upon being exposed to the herbicide. Soybeans, for instance, can sometimes suffer injury from commonly used herbicides such as Sonic, and recognizing signs of herbicide injury is key to protecting the health of your soybeans.
Sonic is the trade name for a broad spectrum herbicide marketed for control of numerous weeds and invasive grasses such as cocklebur, palmer amaranth, kochia, common and giant ragweed, lambsquarter, Russian thistle and many others. The two active herbicide ingredients in Sonic are sulfentrazone and cloransulam-methyl. Sonic is a pre-emerge herbicide, meaning it should be applied to soybean prior to planting and up to 3 days after planting. Sonic is designed to be used especially with Roundup Ready soybeans, soybean strains that have been genetically modified to account for glyphosate tolerance.
Symptoms of Injury in Soybeans
The exact symptoms of herbicide injury in soybean plants vary according to the herbicide chemical being used. Sulfentrazone, one of the active ingredients in Sonic, will cause leaf crinkling and stunted new growth in injury-sensitive soybean plants. Cloransum, an amino acid synthesis inhibitor and the other active ingredient in Sonic, will cause in injured soybeans leaf yellowing and necrotic leaf tissue and purple and red leaf vein colors on the underside of leaves.
Treating Injured Soybean Plants
If you notice injury symptoms in your soybean plants and you suspect that Sonic herbicide may have caused the injury, usually all that is necessary to revive the plants is to avoid using that herbicide until soybean plants have outgrown the damage inflicted by the herbicide. If soybean plants are severely damaged, you may need to dig them up and replace them with less injury-prone cultivars of soybean. If injury symptoms persist throughout successive seasons, you may need to experiment with other herbicides to find one that will offer effective weed control without injuring your soybeans.
One of the best ways to avoid injury on any plants you grow by any herbicide you use is to always follow the manufacturer's labeled instructions exactly. Injury is always an inevitable risk when using an herbicide, but many herbicide injuries to plants are caused unnecessarily be neglecting to apply the herbicide in a manner consistent with the manufacturer's recommendations. Using herbicides exactly according to manufacturer's instructions not only will increase the effectiveness of the herbicide but will avoid injury problems as well.
- Purdue University Cooperative Extension Service: Herbicide Injury Symptoms on Corn and Soybeans
- University of Illinois Extension; Quick Guide to Herbicide Injury on Soybean
- University of Illinois Extension; Plant Growth Regulator Injury to Soybean; Kevin Kelley, et al
- Dow Chemical; New Sonic™ Herbicide for Soybeans
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