[Fhb-update_cgp] FHB Update from OK, 04/29/16

[FHB Update - Central GP, Hard Winter Wheat]

In addition to looking at wheat around Stillwater, field days over this past
week took me to south-central OK (near Walters, OK in Cotton County),
southwestern OK (near Altus in Jackson County), and through central OK (near
Apache in Caddo County and near Kingfisher in Kingfisher County). For the
most part, wheat ranged from full kernel watery to full kernel milky. In the
variety trials I visited, the effects of stripe rust were evident.

Across southern OK, stripe rust was mostly not active (black resting spores
present) or only small amounts of yellowish-orange sporulation was present.
In central OK and around Stillwater, more active sporulation could be found.
However, in all areas the foliage of susceptible varieties (including flag
leaves) was mostly yellow/dead unless a fungicide had been applied. Where a
fungicide had been applied, the foliage had been protected and was mostly
green. In one case (Apache), the fungicide had been applied 1 month ago and
a small amount of sporulation was just starting to appear again on the upper
leaves. However, the fungicide provided a month of protection and will go a
long way toward protecting the yield and test weight even if stripe rust
does come in again. Plus, the later incidence of stripe (or leaf) rust once
the wheat reaches milk or soft dough is much less damaging than if infection
is severe at heading. For more explanation, see Current Report CR-7668
(Foliar Fungicides and Wheat Production in Oklahoma – March 2016) at:
http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-4987/CR-7668web2016.pdf

Another disease that is making an appearance again in Oklahoma this year is
wheat streak mosaic (WSM). This disease, which is cause by the
mite-transmitted Wheat streak mosaic virus (WSMV), infects wheat in the fall
or spring with symptoms occurring in the spring and becoming more severe as
temperature rises. The earlier the infection, the more severe the damage to
the wheat. To date, we have had samples test positive for WSMV from across
northern OK out towards the panhandle. Many of these samples also test
positive for High plains virus and/or Triticum mosaic virus. A couple of the
fields I have seen this year have affected the entire field and likely will
not be harvested. Often WSM occurs because of the lack of control of
volunteer wheat either in the field of production or in an adjacent field.
It is critical to control volunteer wheat and other grassy weeds that serve
as alternative hosts for both the mite (wheat curl mite) and the virus. Also
please note that WSM often is more severe in fields that were hailed on
during the previous season. Typically this is related to a flush of
volunteer wheat. For more information, see Fact Sheet EPP-7328 (Wheat Streak
Mosaic, High Plains Disease, and Triticum Mosaic: Three Virus Diseases of
Wheat in Oklahoma) at
http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-8987/EPP-7328.pdf


--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