Leaf Condition
Marginal Necrosis, Interveinal Necrosis, Stunted
Leaf Color
Yellow, Purple, Marginal Chlorosis, Interveinal Chlorosis, Complete Chlorosis
Leaf Location
Entire, Edge, Young
Petioles Condition
Short Or Stunted
Petioles Color
Plant Size
Field Distribution
Uniform, Random, Edges
Prior Environmental
Organic Soil, Rain, Dry, Wind, High Temp, Pesticide Spray
Early Vegetative, Mid To Late Vegetative
Cropping System
Soybean Followed By Soybean, Conventional Till, Reduced Till


Acetolactate synthase (ALS)-inhibiting herbicides (HG 2) cease the production of branched-chain amino acids, precursors to essential plant enzymes and structures. ALS-inhibiting herbicides can be applied pre- and postemergence. While there are many ALS-inhibiting herbicides labeled for soybeans, injury can still be prevalent. Injury symptomology includes plant stunting, root stunting (i.e. bottle brushing), chlorosis, and purpling of leaf veins. Initial injury can be mistaken for nutrient deficiency; development of ALS-inhibiting herbicide injury on soybeans will be a slow process. The ALS-inhibiting herbicides are phloem mobile which results in injury observed primarily on new plant growth. Injury from the ALS-inhibiting herbicides labeled for soybeans is usually transient, however, ALS-inhibiting herbicides not labeled for soybeans can result in plant death.


Since ALS-inhibiting herbicides can be applied pre- and post-emergence injury can be incurred on emerging and established soybean plants. If soybeans are injured by labeled ALS-inhibiting herbicides, injury will subside over time and no yield loss will occur.

Labeled rotation restrictions should be followed to ensure that soybeans are not injured by carryover of ALS-inhibiting herbicide labeled for other crops and vice versa. Depending on when the previous ALS-inhibiting herbicide was applied, yield losses can range significantly and are often environmentally dependent. Soybeans injured from physical drift from a non-labeled ALS-inhibiting herbicide, incurred injury can vary widely, depending on the dose. Physical drift can be avoided by spraying when the average wind speed is less than 10 miles an hour and mid-day or –afternoon to avoid a temperature inversion.


Extension Weed Specialist and Associate Professor
Crop & Soil Sciences
Graduate Research Assistant
Crop and Soil Sciences
 This NC State FactSheet can be viewed and printed at https://content.ces.ncsu.edu/als-inhibiting-herbicide-injury-on-soybean.
NC State Extension