What’s Causing the Bleached Heads in My Wheat Crop?

Based on archived post from September 2014

In 2012 and 2014 bleached, white heads showed up in wheat, barley, and oat fields across Manitoba.  It appears the bleached heads are making a reappearance in 2015.

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White heads caused by root rot. (Image: Kansas State University)

There are a number of things that could be the cause:

  1. Insect damage – One of the tests to see if a white head is potentially wheat stem maggot is to try to pull the head out of the stem. If the head pulls out easily, it could be because a larva of wheat stem maggot has severed the stem, resulting in the head turning white. Larvae may be present above the top node.  See Manitoba Agriculture’s website for more information on wheat stem maggot:  http://www.gov.mb.ca/agriculture/crops/insects/wheat-stem-maggot.html
  2. Root rot – infected plants will generally pull free from the soil without much resistance. In years where the plants are under stress due to either lack of moisture or excess moisture, a loss of root tissue from root rots will have a much larger impact.
  3. Fusarium head blight – if seed is produced they are smaller, chalky, and can be shrivelled. Pink or orange mycelium may be visible at the base of the glumes.
  4. Aster yellows – infected plants show white heads, but green stems and seemingly healthy root systems.
  5. Environmental stress – high temperatures, bright sunlight, and hot winds can results in white, empty heads.

Additional information can be found in the July 27, 2012 issue of Manitoba Agriculture’s Manitoba Insect & Disease Report available at: http://www.gov.mb.ca/agriculture/crops/miu/2012/2012-07-27/report.pdf

Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist, Manitoba Agriculture

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Seeing Leaf Tip Burn in Your Cereal Fields?

Manitoba Agriculture’s Crop Diagnostic Lab receives several spring wheat samples over the growing season.

This post is from June 2013 where the lab had received samples showing symptoms where leaf tips are yellowing and necrotic.  Rejean Picard with Manitoba Agriculture in Somerset, submitted this photo from a field in his area.  He noted the symptoms appeared with the warmer temperatures and was evident in localized areas of several fields.

Leaf Tip Burn/Necrosis in Wheat
Photo by Rejean Picard, Manitoba Agriculture, Somerset

Mardi Desjardins, the former Crop Diagnostic Specialist, had 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.

Wind and/or high temperature can result in injury of leaf tips of small grains
Credit: Photo Library of Manitoba Agriculture’s Crop Diagnostic Lab Reports (2009)

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.  Back in 2013, most reports in Manitoba indicated symptoms were on the flag leaf, with one case where symptoms also appeared on the penultimate leaf.

In the United States, the severity of leaf tip necrosis has been noted to be dependent on both the growing conditions during flag leaf emergence and the variety.

Unfortunately, there is little information reported in the literature whether this type of damage causes any yield losses.

Submitted by:  Pam de Rocquigny, Provincial Cereal Crop Specialist, Manitoba Agriculture

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