[Fhb-update_cgp] FHB Update from OK, 04/16/16

[FHB Update - Central GP, Hard Winter Wheat]

I had limited trips outside of Stillwater this past week, and only was able
to contact one County Educator before writing this today. Wheat around
Stillwater is mostly at various stages of head emergence. I did see a few
anthers on scattered heads, but not many. By contrast, Aaron Henson (County
Educator; Tillman County in south-central OK) indicated wheat in his area is
mostly at flowering.

During this past week, I had several calls about spraying wheat with a
fungicide. Although rust (stripe and leaf rust) didn’t appear to increase
this past week, conditions reverted to being more favorable for stripe rust
development with rainfall, increased dews, and favorable temperature. With
more rains and cool temps in the forecast, stripe rust could
“reactivate” again, and leaf rust will start to come into the picture.
Wheat is now at the point where it will quickly move past the stage (the
start of flowering) where it can be sprayed with most fungicides. As far as
I know, all wheat foliar fungicides (with the exception of Prosaro) must be
applied prior to the start of flowering (Feekes’ growth stage 10.5).
Prosaro can be applied through growth stage 10.5.1, which is when flowering
is just starting (anthers emerged mostly from the middle of heads). Be sure
to read all labels regarding a fungicides use on wheat. There also are
varying pre-harvest intervals (PHIs) required for the various fungicides,
and often the length of time from heading to harvest can be short in
Oklahoma. So, be aware of these PHIs, and spray accordingly.

Active sporulation of stripe rust still can be found around Stillwater and
the surrounding area. Stan Fimple (County Educator, Pawnee County just to
the northeast of Stillwater) sent me photos showing active stripe rust.
Other than this, I have seen scattered leaf rust pustules on lower leaves
around Stillwater, and powdery mildew also has become more apparent around
Stillwater and at Lahoma as reported by Dr. Brett Carver (OSU Wheat
Breeder). However, both of these diseases are at low levels on lower leaves
but with coming rain and cool temperatures both (especially leaf rust) could
continue to increase on the upper canopy. Around Stillwater, barley yellow
dwarf spots continue to be observed but the aphids are now gone or at least
in much lower in frequency. If heavy rains come over the next 3 or so days,
I would imagine aphid populations will be mostly eliminated.

Finally, I want to raise awareness once again to Fusarium head blight (scab)
of wheat. When wheat flowers it is susceptible to infection by the Fusarium
fungus that causes scab. That time is quickly approaching. Occasionally
Oklahoma has problems with this disease, typically more so in
eastern/northeastern Oklahoma than through the central and western parts of
the state. However, scab was severe across the state for a couple years
around 2010 and there also was some reported last year. For more information
on scab, please see PSS-2145 (Fusarium Head Blight (Head Scab) of Wheat:
Questions & Answers) and PSS-2136 (Considerations when Rotating Wheat Behind
Corn) that can be found at:
http://pods.dasnr.okstate.edu/docushare/dsweb/HomePage. Once at that page,
type the identifiers (PSS-2145/PSS-2136) into the “search box” located
in the upper right area of the screen. An additional resource is the
Fusarium Head Blight Prediction Center at http://www.wheatscab.psu.edu/. At
this site you can read commentaries submitted by specialists from each state
but more importantly see if weather conditions in your area have been
conducive to development of FHB. The site is easy to use and especially may
be beneficial in helping make fungicide application decisions.


--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