Identifying Glyphosate Drift Injury on Wheat Plants

Off-target movement and deposition of herbicides, such as glyphosate, may potentially damage productivity of sensitive crops.  Missisissippi’s winter wheat acreage this season is much higher than the past several years and lately we are seeing considerable instances and reports of potential glyphosate drift in wheat fields.

Moderate glyphosate drift typically bleaches or whitens the lower portion of young leaves and may exhibit an interveinal pattern.

Moderate glyphosate drift on wheat produces symptoms primarily characterized by bleached or white tissue normally localized in the lower section of upper leaf blades near the collar.  Minor leaf wrinkling, wrapping or cupping is also common on wheat when drift occurs during vegetative growth stages. Slight to moderate glyphosate drift injury is normally localized on youngest, uppermost leaves emerging on the plant.  Injury symptoms are also normally quite variable from plant to plant.

Although some nutrient deficiencies, such as zinc, sulfur or iron, may bleach leaf tissue of young leaves, drift injury is typically much more localized on specific leaves or even a section of leaf.  While these nutrient deficiencies should be most pronounced in young leaves, compared to older or lower leaves, symptoms are generally apparent spread over substantial plant tissue.  Furthermore, onset of nutrient deficiency is usually gradual and can often be distinguished by analyzing soil nutrient levels, soil properties, and their interaction with environmental conditions.  Considering that environmental conditions have generally been quite favorable for wheat growth this spring, such nutrient deficiencies are not particularly likely, or would likely be isolated in nature.

Glyphosate drift symptoms are typically quite localized on uppermost wheat leaves.

Stunted plant growth resulting from herbicide drift is typically much more abrupt and distinctive to a finite time period, compared to nutrient deficiencies.  These symptoms or injury can often be correlated to a time frame or plant growth stage when herbicide drift occurred.

Glyphosate drift will often stunt the flag leaf causing the head to bend over as it attempts to emerge from the injured sheath.

Herbicide injury to wheat during spring vegetative growth stages typically stunts normal leaf development and emergence of subsequent organs.  Thus, stunted, twisted, restricted and/or malformed vegetative growth and seed heads may be common.