Updated from Archived Crop Chatter post made June 28, 2013
I have received a few reports over the past couple of days where spring wheat are showing symptoms where flag leaf tips are yellowing and necrotic. Amir Farooq, Farm Production Extension Specialist from Hamiota, submitted this photo from a field in his area. He noted the symptoms appeared with the warmer temperatures.
Manitoba Agriculture’s Crop Diagnostic lab technician has seen similar symptoms in previous seasons when environmental conditions have caused rapid moisture loss from the leaves, i.e. windy weather combined with warm/hot temperatures. The result is leaf tip burn or necrosis.
Leaf tip necrosis normally progresses from the margins of the flag leaf tip and lower leaves should show some signs of it as well. Note that leaf tip burn caused by wind and/or hot temperature injury can appear similar to the damage of contact herbicides, fungal diseases, viral diseases (BYDV), foliar fertilizer burn or soil salinity. However, with wind and/or hot temperatures, damage is often limited to the newest, just emerging, leaf tips. Most reports to date in Manitoba indicate symptoms are on the flag leaf.
Symptoms of leaf tip necrosis can also be observed to some extent in all wheat varieties containing the leaf rust resistance gene Lr34. The leaf tip necrosis can be more pronounced after cooler weather, such as cooler evening temperatures.
The severity of the leaf tip necrosis is dependent on both the variety and the growing conditions during flag leaf emergence and early grainfill and thus some varieties have a tendency to show a lot more leaf tip necrosis than other.
Unfortunately, there is little information reported in the literature whether this type of damage causes any yield losses. However, the remainder of the canopy has a great ability to compensate for this type of physiological damage. In either case, there is nothing producers can do to avoid or alleviate the symptoms.
Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist, Manitoba Agriculture
Source: “Flag Leaf Burning: Hot Weather and Leaf Tip Necrosis in Wheat” by Jochum Wiersma, University of Minnesota