Photosystem II Inhibitor (HG 5) Herbicide Injury in Soybean
Published: 09/08/2023
Photosystem II inhibitors, or Group 5 herbicides, interfere with photosynthesis by preventing the binding of photosystem II proteins, stopping the electron flow that creates energy production, causing rapid deterioration of cells and possible interference with other plant processes.
One of the most distinguishable symptoms of Group 5 herbicide injury is interveinal chlorosis of leaves followed by necrosis. Symptoms are more severe near the leaf margins, appearing to move from the outside of the leaf inward. Soil-applied herbicide injury symptoms will not appear until after photosynthesis begins, appearing on older leaves which slowly become yellow with green veins. Foliar-applied injury symptoms may occur as early as three days after exposure, as leaf burning. Over time, affected leaves may drop off the plant completely.
Photosystem II inhibitor injury on soybean.
Kristine Schaefer
Atrazine injury on soybean.
Cal Shumway, Bob Scott, and John Boyd, www.uada.edu.
Soybean cultivars have varied tolerance to metribuzin (ranging from very sensitive to very tolerant) and injury is more likely to occur on high pH, coarse textured soil with low OM. Atrazine injury may also occur on soybean due to carryover and physical drift or tank contamination.
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.
Atrazine injury to soybean. By Cal Shumway, Bob Scott, and John Boyd, www.uada.edu.
Atrazine injury to soybean. By Cal Shumway, Bob Scott, and John Boyd, www.uada.edu.
Propanil injury to soybean. By Cal Shumway, Bob Scott, and John Boyd, www.uada.edu.
Fluometuron injury to soybean. By Cal Shumway, Bob Scott, and John Boyd, www.uada.edu.
Metribuzin injury to soybean. By Cal Shumway, Bob Scott, and John Boyd, www.uada.edu.
Photosystem II inhibitor injury on soybean. By Kristine Schaefer.
Atrazine injury to soybean. By Cal Shumway, Bob Scott, and John Boyd, www.uada.edu.
Gallery images courtesy Kristine Schaefer, Iowa State University and Cal Shumway, Bob Scott, and John Boyd, www.uada.edu.
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