University of Missouri Extension

IPM1007, Revised November 2009

Practical Weed Science for the Field Scout: Corn and Soybean

Growth regulators

Injury from dicamba can cause stems to form callus tissue. Snap bean shown. Injury from dicamba can cause stems to form callus tissue. Snap bean shown.
 

Early applications of dicamba + atrazine with a sulfonyl­urea herbicide and methylated seed oil resulted in this severe case of onion-leafing on corn.Early applications of dicamba + atrazine with a sulfonyl­urea herbicide and methylated seed oil resulted in this severe case of onion-leafing on corn. Early applications of dicamba + atrazine with a sulfonyl-urea herbicide and methylated seed oil resulted in this severe case of onion-leafing on corn.
 

Leaf cupping caused by dicamba drift or dicamba-contaminated spray tank. Sometimes the mottled appearance can be confused with certain viruses of soybean.
Leaf cupping caused by dicamba drift or dicamba-contaminated spray tank. Sometimes the mottled appearance can be confused with certain viruses of soybean. Leaf cupping caused by dicamba drift or dicamba-contaminated spray tank. Sometimes the mottled appearance can be confused with certain viruses of soybean.
 

Stalk twisting and leaning after dicambe. Stalk twisting and leaning after dicambe. Stalk twisting and leaning after dicambe.
Green snap caused by high winds shortly after dicamba applications.

Green snap caused by high winds shortly after dicamba applications.
 

Dicamba and dicamba-containing products can also cause brace root fusion in corn with late postemergence applications. Dicamba and dicamba-containing products can also cause brace root fusion in corn with late postemergence applications.
 

Postemergence applications of dicamba can sometimes cause corn leaf rollling and mimic drought stress. Postemergence applications of dicamba can sometimes cause corn leaf rollling and mimic drought stress.
 

Draw-stringed leaves can also occur when proper rotational intervals are not followed with dicamba or clopyralid. Draw-stringed leaves can also occur when proper rotational intervals are not followed with dicamba or clopyralid."Draw-stringed" leaves can also occur when proper rotational intervals are not followed with dicamba or clopyralid (Stinger, Hornet).
 

Benzoic acids and pyridines chemical group

Herbicides

Mode of action and characteristics of activity

General symptoms

Injury from 2,4-D on soybeans appears as strapped leaves, irregular bending in the stems, and formation of callus tissue on the stem.
Injury from 2,4-D on soybeans appears as strapped leaves, irregular bending in the stems, and formation of callus tissue on the stem. Injury from 2,4-D on soybeans appears as strapped leaves, irregular bending in the stems, and formation of callus tissue on the stem.
 

Injury from Harness + 2,4-D tankmixes on spike-stage corn.
Injury from Harness + 2,4-D tankmixes on spike-stage corn.Injury from Harness + 2,4-D tankmixes on spike-stage corn.
 

Soybean injury can also occur when proper intervals are not followed after burndown with 2,4-D.
Soybean injury can also occur when proper intervals are not followed after burndown with 2,4-D. Soybean injury can also occur when proper intervals are not followed after burndown with 2,4-D.
 

2,4-D injury on corn appears as brittle stems, rolled up leaves (onion-leafing) and fused brace roots.
2,4-D injury on corn appears as brittle stems, rolled up leaves (onion-leafing) and fused brace roots. 2,4-D injury on corn appears as brittle stems, rolled up leaves (onion-leafing) and fused brace roots. 2,4-D injury on corn appears as brittle stems, rolled up leaves (onion-leafing) and fused brace roots.
 

Phenoxy acetic acid chemical group

Herbicides

Mode of action and characteristics of activity

General symptoms

IPM1007, revised November 2009

IPM1007 Practical Weed Science for the Field Scout: Corn and Soybean | University of Missouri Extension

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