ALS (HG 2) Inhibitor Herbicide Injury in Soybean
Published: 09/08/2023
Acetolactate synthase (ALS) inhibitors, also referred to as Group 2 herbicides, catalyze the first step in the biosynthesis of branched-chain amino acids. Symptoms of plant injury include stunting, chlorosis of new trifoliates, and/or reddish leaf veins typically visible on the underside of the leaves. Other symptoms are yellowing of the margins, crinkled leaves, stacked or shortened internodes, and reduced root system with bottle brush roots or root pruning. Symptoms typically first appear in the newest growth of the soybean plant. Symptoms can be confused with those caused by nutrient issues such as iron or potassium deficiency.
Halosulfuron injury to soybean.
Cal Shumway, Bob Scott, and John Boyd, www.uada.edu.jpg.
Leaf yellowing caused by ALS herbicide.
Kristine Schaefer
Symptoms may occur following application during high temperatures and high humidity. In these cases, plants often recover with no yield loss. Injury may be caused by carryover of herbicide and is more likely to occur when winter weather results in soils that are cooler and/or drier than expected. Sulfonylurea chemistries are more likely to carryover in high pH soils, while imidazolinone chemistries are more likely to carryover in low pH soils. Soybean varieties with STS (sulfonylurea tolerant soybean), SR (sulfonylurea ready), or BOLT™ traits have an increased tolerance to sulfonylurea herbicides and are less susceptible to carryover injury. Injury can also occur when ALS-herbicides are applied either sequentially or in a tank-mix with organophosphate insecticides.
See the Herbicide Classification Chart from Take Action for herbicide selection information to help slow the development of resistant weeds.
Prepared and reviewed by Dr. Thomas (Tommy) Butts, University of Arkansas; Dr. Joe Ikley, North Dakota State University; the Integrated Pest Management Program at Iowa State University; Dr. Sarah Lancaster, Kansas State University; Dr. Travis Legleiter, University of Kentucky; and Dr. Rodrigo Werle, University of Wisconsin-Madison.
Primisulfuron injury to soybean. By Cal Shumway, Bob Scott, and John Boyd, www.uada.edu.
Chlorsulfuron injury to soybean. By Cal Shumway, Bob Scott, and John Boyd, www.uada.edu.
Trifloxysulfuron injury to soybean. By Cal Shumway, Bob Scott, and John Boyd, www.uada.edu.
Imazaquin injury to soybean. By Cal Shumway, Bob Scott, and John Boyd, www.uada.edu.
Penoxsulam injury to soybean. By Cal Shumway, Bob Scott, and John Boyd, www.uada.edu.
Prosulfuron injury to soybean. By Cal Shumway, Bob Scott, and John Boyd, www.uada.edu.
Bispyribac injury to soybean. By Cal Shumway, Bob Scott, and John Boyd, www.uada.edu.
Bispyribac injury to soybean. By Cal Shumway, Bob Scott, and John Boyd, www.uada.edu.
Trifloxysulfuron injury to soybean. By Cal Shumway, Bob Scott, and John Boyd, www.uada.edu.
Orthosulfamuron injury to soybean. By Cal Shumway, Bob Scott, and John Boyd, www.uada.edu.
Leaf yellowing caused by ALS herbicide. By Kristine Schaefer.
Halosulfuron injury to soybean. By Cal Shumway, Bob Scott, and John Boyd, www.uada.edu.jpg.
Gallery images courtesy Kristine Schaefer, Iowa State University and Cal Shumway, Bob Scott, and John Boyd, www.uada.edu.jpg.
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