[Fhb-update_cgp] FHB Update from OK, 05/15/15

[FHB Update - Central GP, Hard Winter Wheat]

Early this week I spent time around Stillwater, Lahoma (10 miles west of
Enid), and Cherokee and Alva (north-central OK not far from the Kansas
border). Wheat ranged from soft dough around Stillwater to milk at Alva (but
quickly approaching dough). There is a big difference between the wheat in
these areas; obviously wheat around Alva suffered more drought stress than
Cherokee, which is worse than Lahoma or Stillwater. However, lots of
moisture and cool temperatures are allowing wheat to fill and mature.

As expected, leaf rust has exploded around Stillwater, with susceptible
varieties such as OK Bullet at 80-90S. Leaves are gone on varieties that
were highly susceptible to stripe rust, but varieties with stripe rust
resistance that are susceptible to leaf rust (e.g., Jackpot, Greer) are now
hit hard with leaf rust.

Weather since the middle of April has been reminiscent of the weather in
April and May of 2007. As a result, wheat diseases favored by cool and wet
weather are starting to occur with increasing frequency and severity. These
diseases are causing head discoloration, which can be caused by fungi or
bacteria. Around Stillwater and Lahoma, head discoloration due to a
bacterium (Xanthomonas) has been observed. l have had reports of similar
symptoms on wheat in southwestern OK, where more rain has fallen then around
Stillwater. This bacterial disease is called black chaff when on the heads
and is called bacterial streak when symptoms are expressed on leaves. The
fungi Septoria and Stagonospora also can cause head discoloration, and we
have isolated Septoria from several samples during the last week or so. For
a full discussion of the various causes of head discoloration along with
pictures, clicking on the following link will take you to the e-Pest Alert
sent out in June, 2007.
http://entoplp.okstate.edu/pddl/pddl/2007/PDIA6-17.pdf

Barley yellow dwarf also was observed this past week, but it was not
extensive and little to no stunting was associated with the BYD spots
indicating infection most likely occurred in the spring.

I have had reports of Fusarium head blight (scab) from southeastern KS, from
Arkansas, and from eastern/northeastern OK, but have had no reports from
anywhere else in Oklahoma.

The diagnostic lab continued to receive multiple samples that tested
positive for Wheat streak mosaic virus, with several also testing positive
for High plains virus (Wheat mosaic virus) and Barley yellow dwarf virus.
For information on mite-transmitted diseases, I refer you to EPP-7328 (Wheat
Streak Mosaic, High Plains Disease, and Triticum Mosaic: Three Virus
Diseases of Wheat in Oklahoma) also available at
http://osufacts.okstate.edu.


--Bob Hunger, Extension Plant Pathologist, Oklahoma State University

For more details, go to the FHB Risk assessment tool at
http://www.wheatscab.psu.edu

For the latest news and updates from the U.S. Wheat & Barley Scab
Initiative, go to http://www.scabusa.org