Herbicide Injury Symptoms

Growth Regulators

Common Herbicides in the Group:

• 2,4-D

• MCPA

• MCPP

• cloypalid (Stinger)

• triclopyr (Garlon, Turflon)

• dicamba (Banvel)

• picloram (Tordon)

• 2,4-DB

How Applied:

Mostly foliar applied, some soil activity.

Movement in the Plant:

Move readily in the phloem with carbohydrates which are being synthesized in the leaves. Movement is to areas where carbohydrates are being utilized for growth in the short tips and buds or for storage in stem and root tissue. Movement can also occur with mineral nutrients and water upward in the xylem.

Mode of Action:

Mimic natural plant auxins causing abnormal growth and disruption of the transport tissue.

Common Symptoms:

Twisted, malformed leaves and stems, callus-like growth on young woody stems.

Effects of Growth Regulators:

The bean plant on the left had been treated with a low concentration of 2,4-D ten days earlier. Note the twisted leaf petioles and cupped leaves.

Many broadleaf plants show severe leaf malformation when exposed to this group of herbicides. Even concentrations of just a few parts per million can result in injury. Spray drift of 2,4-D onto sensitive crops during critical periods can results in the type of injury seen here on grapes.

Exposure to this group of herbicides also can cause adventitious stem growth which causes restrictions in the vascular or transport system of the plant. Exposure to triclopyr has resulted in abnormal stem growth, with swelling and splititng seen here in grapes.