PPO Inhibitor (HG 14) Herbicide Injury in Soybean
Published: 09/08/2023
Protoporphyrinogen oxidase (PPO) inhibitors, or Group 14 herbicides, are labeled for preemergence as well as postemergence applications in soybean. These herbicides interfere with the production of chlorophyll for photosynthesis and rapidly destroy tissue. Cell membranes are disrupted by the accumulation of peroxidative agents caused by these herbicides.
Symptoms of herbicide injury from preemergence PPO applications are usually due to one of three causes: herbicide being splashed or washed onto tissue at or just after emergence, poor furrow closure allowing herbicide to be applied or washed directly into a furrow following a rainfall, or slow metabolism by soybeans during prolonged cold and wet periods. Tissue develops necrosis, which may be noticeable on the hypocotyl or cotyledons, and in some cases, hypocotyls may be girdled resulting in plant death. Slow metabolism can also result in a crumpled or crimped leaf appearance, similar to a crumpled paper bag. Soybean normally recovers from these injury symptoms quickly, unless the hypocotyl is girdled, or the apical bud is damaged and no axillary buds have developed. Bronzing or necrotic speckling of new trifoliates can persist for several weeks. Increased risk of injury from preemergence PPO-inhibiting herbicides occurs on coarse and low organic matter soils. Soybean cultivars also vary in sensitivity to sulfentrazone, saflufenacil, and flumioxazin applied preemergence.
PPO inhibitor injury to soybean.
Kristine Schaefer
PPO inhibitor injury to soybean.
Kristine Schaefer
Postemergence use of PPO herbicides leads to speckling or necrotic tissue that the herbicide contacts. Injury is most likely to occur when postemergence applications are made during hot, humid weather or if long periods of cold temperatures follow application. Symptoms caused by PPO herbicides can be confused with soybean foliar diseases such as Cercospora leaf blight, frogeye leaf spot, and Septoria brown spot. Postemergence PPO injury is typically not yield-limiting if the product label is followed.
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.
Fomesafen injury to soybean. By Cal Shumway, Bob Scott, and John Boyd, www.uada.edu.
Carfentrazone injury to soybean. By Cal Shumway, Bob Scott, and John Boyd, www.uada.edu.
Carfentrazone injury to soybean. By Cal Shumway, Bob Scott, and John Boyd, www.uada.edu.
Lactofen injury to soybean. By Cal Shumway, Bob Scott, and John Boyd, www.uada.edu.
Acifluorfen injury to soybean. By Cal Shumway, Bob Scott, and John Boyd, www.uada.edu.
PPO inhibitor injury to soybean. By Kristine Schaefer.
PPO inhibitor injury to soybean. By Kristine Schaefer.
Gallery images courtesy Kristine Schaefer, Iowa State University and Cal Shumway, Bob Scott, and John Boyd, www.uada.edu.
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