Herbicide and Nonherbicide Injury Symptoms on Spring Wheat and Barley

Unclassified
The last two small grain herbicides are categorized as unclassified because they do not have common characteristics that could be used to place them in a specific herbicide family.

Difenzoquat (Avenge)
Application Timing (spring wheat and barley): Wheat, 3- to 5-leaf wild oats (wheat is usually 5- to 6-leaf stage); barley, 3- to 5-leaf wild oats (barley is usually 2- to leaf). Barley is very tolerant to Avenge, but selectivity to hard red spring wheat is cultivar (variety) dependent.
Injury Symptoms: Common injury symptoms appear on leaf tips as chlorosis or necrotic burn spots that develop soon after application. Leaf tip burn or yellowing occurs on hard red spring wheat and barley 5 to 8 days following Avenge application. This injury symptom is temporary and disappears in about two weeks. Crop injury potential from Avenge can be heightened if temperatures exceed 85°F following application. The most common time for this injury to occur are the first three days following application. See photos 19 and 20.
Site of Action: Unknown and believed to have multiple sites.

Photo 19 Avenge can cause leaf burn and leaf necrosis under hot, dry conditions. This injury is usually temporary and disappears as new leaves emerge.

Photo 20 Avenge can only be applied to labeled varieties of spring wheat. Application of Avenge to sensitive varieties will result in severe injury or death.

Propanil (Stampede)
Application Timing (spring wheat and barley): Wheat, postemergence from the 2- to 5-leaf stage; barley, postemergence from the 2- to 4-leaf stage.
Injury Symptoms: Injury appears as leaf tip burn, leaf necrosis, and reduced plant height. Hard spring wheat and barley tolerance is influenced by crop growth stage, post-treatment temperatures, and tank mixes. Hard red spring wheat height reductions may be greater following treatment at the 5-leaf rather than the 2-leaf stage. Temperatures greater than 86°F that soon follow treatment can lead to more leaf tip burn and necrosis. Tip browning and yellowing can appear on foliage 2 to 5 days after application and will generally last about two weeks. Applications of Stampede made under adverse growing conditions can cause more severe crop injury and delay the recovery time. Crop injury to small grains may also occur if frost immediately follows an application of Stampede. See photo 21.
Site of Action: Multiple sites-photosynthesis, RNA synthesis, and protein synthesis.

Photo 21 Stampede causes leaf burn, yellowing, and stunting. Injury is usually temporary and will disappear as new leaves emerge (10-14 days).

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