Quick Guide to Herbicide Injury on Soybean

Plant Growth A B C D Regulators

Ex. dicamba, 2,4-D, 2,4-DB, and clopyralid Protox(PPO) A B C D Inhibitors

Ex. lactofen, fome- safen, carfentrazone, and acifl uorfen

Amino Acid A B C D Synthesis Inhibitors

Ex. imazethapyr, clo- ransulam, chlorimu- ron, and glyphosate

Photosystem I A B C D and II Inhibitors

Ex. atrazine, bentazon, metribuzin, and paraquat

Others A B C D

Ex. trifl uralin, quiza- lofop, glufosinate, me- sotrione, acetochlor, and S-metolachlor

Images are identifi ed on the back of sheet. IWM 3-3 June 2005 Quick Guide to Herbicide Injury on Soybean Symptoms can vary depending on the respective herbicide and the route (soil or foliar) of soybean exposure to the herbicide.

Plant Growth Injury Symptoms: Regulator Images: Injury is fi rst noticed on newly developed tissue or leaves. A) dicamba Stunting and inhibition of roots; improper root development. B) dicamba Translocated in xylem and phloem. C) clopyralid Stunted and cupped leaves; strapping of veins; paralle venation. D) severe cupping Twisting of stems and petioles (epinasty). PPO Inhibitor Injury Symptoms: Images: Little translocation following foliar application. A) fomesafen Contact leaf burn from foliar application. B) sulfentrazone Leaf crinkling and plant stunting. C) carfentrazone Injury typically increased with humidity and temperature. D) fl umioxazin Stem lesions from soil-applied treatments. Amino Acid Injury Symptoms: Inhibitor Translocated in xylem and phloem. Images: Stunted plants. A) thifensulfuron Slow development of symptoms following foliar applications. B) chlorimuron Leaf yellowing or chlorosis of leaf margins. C) prosulfuron Purple to dark red veination on the underside of leaf. D) glyphosate May resemble potassium defi ciency of soybean cyst nematode.

Photosystem I Injury Symptomsptoms: and II Inhibi- Little (xylem) to no translocation following foliar applications. tor Images: Triazines: leaf margin burn and interveinal chlorosis; older leaves affected fi rst. A) metribuzin Paraquat: Water-soaked early; chlorosis and necrosis of leaf tissue; exposure via B) paraquat drift occurs as speckling; symptoms develop quickly. C) bentazon Others: Necrotic spots, speckled chlorosis, or bronzing. D) atrazine Symptoms often increase in severity with increased humidity and air temperature.

Others Injury Symptoms: Images: Pigment Inhibitors: Bleaching and whitening of plants; eventual necrosis. A) S-metolachlor Chloroacetamides: Leaf crinkling and drawstring. B) quizalofop Thiocarbamates: Leaf crinkling and puckering; bud-seal. C) isoxafl utole Dinitroanalines: Swollen and cracked hypocotyls; stunted plants; crinkled leaves; D)D) mmesotrioneesotrione Callus tissue from soil splash; may cause lodging and breakage; stubby roots.

Authors: Dawn Nordby and Aaron Hager June 2005 University of Illinois Weed Science Extension Department of Crop Sciences