Thursday, May 28, 2015

Wheat Disease Update

Spring and Winter Wheat

1) Stripe rust 

Stripe rust is being reported from a widespread area, including northern Utah, western Idaho, southern Idaho (Twin Falls and Burley / Rupert area) and now eastern Idaho (Newdale and Blackfoot).

All reports so far have been in Brundage soft white winter wheat.

Brundage is very susceptible. If you have not be applying fungicides to this variety up to now, I would consider it infected and treat with a triazole fungicide which has some curative activity.

Strobilurin products may have reduced efficacy on stripe rust if the plants are already infected.

The Pre-Harvest Interval (PHI) has been reached in some winter wheat production at which time it is too late to apply fungicides. Always follow label directions.

Spray appropriate fungicides on susceptible spring wheat varieties at herbicide application.  

2) Barley Yellow Dwarf Virus

Barley yellow dwarf symptoms are re-occurring in infected fields. Expect to see flag leaves with the typical yellow and red “flags”. For more information, see and click on publications to download the BYD bulletin published by the UI. The heavy rains have really helped to mitigate the damage.

3) Russian Wheat Aphids

Russian Wheat Aphids are damaging wheat in several areas - look for white (bleached) stripes on tightly curled leaves, and trapped heads which appear similar to frost damaged heads. We are seeing frost damage (which is the likely cause in the picture below) and RWA damage in wheat. RWA will colonize both wheat and barley.

Saturday, May 16, 2015

Stripe Rust Spring Wheat Western Idaho Update

By Juliet Marshall, Cereal Pathologist and Agronomist

1776 Science Drive Suite 205, University of Idaho Idaho Falls R&E Center, Idaho Falls, ID 83402

PROTECT susceptible spring wheat with fungicides applied at herbicide timing. A fungicide efficacy chart is below. Variety ratings of spring wheat to stripe rust in 2014 are available in the 2014 Small Grain Research Report (also on our website). This cool, wet weather will allow rapid spread and infection to occur.

Stripe rust is spreading in western Idaho. Stephens is widely grown in western Idaho and is susceptible to stripe rust. Fields are being sprayed with fungicides but are getting close to the cut-off point for spraying with specific fungicides. Be aware of the PHI (pre-harvest interval) associated with the fungicide being applied - in some cases the PHI restriction may not be when crop is 50% flowering, but before. Know the crop growth stage prior to application to avoid residue issues and off-label applications. 
A white-chaffed, semidwarf, widely adapted variety released by Oregon AES, USDA-ARS in 1977. Stephens dominated the Pacific Northwest during the 1980's and continues to be the most commonly grown wheat in the Treasure Valley  where Cephalosporium Stripe and Septoria do not limit production. Stephens is high-yielding and has an average level of winter hardiness.  It is especially adapted in the Treasure Valley when late planted in November following beets or potatoes. It is very resistant to lodging, stripe rust, leaf rust, and smut. It is susceptible to dwarf smut (TCK), flag smut, snow mold, Cephalosporium stripe, and Septoria tritici. In areas where winter hardiness and Cephalosporium tolerance are important, it is recommended to not grow large acreages of Stephens. Varieties with better winter hardiness and Cephalosporium tolerance should be used in these areas. Milling/baking quality of Stephens is good.   Stephens is relatively early but not as early as Brundage. Stephens has medium height and has proven to be too tall under favorable conditions for some low profile sprinkler systems such as wheel lines.
Brundage is also very susceptible to stripe rust, and Brundage fields in Twin Falls county are showing infection. 

Released by Idaho AES, USDA-ARS in 1997.  It is shorter and earlier heading than Stephens and has excellent straw strength and lodging resistance.  It is awnless.   Brundage has not  exceeded Stephens in yield.  It  has lower protein percentage under favorable conditions.   Brundage may have a greater vernalization requirement than Stephens and therefore may be slower to tiller in the spring.  It is most competitive when early fall planted so that fall tillers may develop.  Brundage is also more sensitive to early spring moisture stress than Stephens.  It is better adapted to early fall than late fall plantings.  Brundage has excellent test weight, 2-3 lb/bu higher than Stephens, Malcolm and MacVicar. Brundage has excellent soft wheat quality.

Fields near Hansen, ID are showing severe BYD and starting to show stripe rust. Fields heavily infected with BYD and showing signs of stripe rust development will probably not be worth spraying with fungicides!! Depending upon the level of BYD, It would be wise to green chop those fields for feed and plant another crop. Check green chop materials for nitrate levels prior to feeding.
 Please  report information on rust (and other diseases) to Juliet Marshall:
Idaho Falls R&E Center
1776 Science Drive Suite 205
Idaho Falls, ID 83402
208-529-8376 office

Please include the following in your report:

include variety, crop growth stage and approximate location.

Photo by Clay Seamons