[Fhb-update_ma] FHB Update from VA, 05/01/15

FHB Updates - Mid Atlantic SWW Region fhb-update_ma at scabusa.org
Fri May 1 15:14:13 EDT 2015


Wheat in the southeastern portions of Virginia will start flowering soon if
it has not already. Wheat is susceptible to scab (Fusarium head blight) from
early flowering until approximately 10 days after first flower. The risk
model is based primarily on relative humidity during the 15 days prior to
flowering since high moisture favors inoculum production by the scab fungus
on crop residues. However, the model also takes into consideration variety
resistance to scab. No wheat varieties have complete resistance (immunity)
to scab, but commercially available varieties vary in their susceptibility.
Current variety rankings for scab resistance can be found on the Virginia
Cooperative Extension website. If you do not know the relative
susceptibility/resistance of your variety, it is probably best to err on the
side of caution and assume that your wheat crop is susceptible or at least
moderately susceptible to scab. Currently, the predicted scab risk for wheat
that is flowering in Virginia is low for all but the most susceptible
varieties. Dry weather is predicted after the current storm passes through,
so scab risk will likely remain low to moderate over the next week. However,
it is prudent to be prepared to apply a fungicide for scab management as the
wheat crop approaches the flowering growth stage. Keep in mind the best
management tactic for minimizing yield and quality losses to scab and DON is
to plant resistant varieties and to make a properly timed fungicide
application when wheat is in the susceptible growth stage (flowering) and
weather conditions favor dispersal of the scab fungus. If a fungicide is
applied for scab, strobilurins should NOT be used as they may increase DON
(vomitoxin) contamination of the grain if applied after flag leaf. Foliar
diseases are starting to increase in some fields in Virginia, but if the
wheat is at or near flowering, a strobilurin or premix fungicide containing
a strobilurin is not recommended. Fungicides recommended for scab also
provide very good to excellent control of common foliar diseases of wheat
(see last week’s post), so a scab fungicide application may provide the
added benefit of controlling leaf spots and rusts. The triazole fungicides
Prosaro, Proline, and Caramba are the most effective fungicides for scab and
should be applied at early to mid-flowering and up to one week later. For
maximum efficacy, fungicides for scab and DON control should be applied with
nozzles angled at a 30 degree angle from the horizontal using both front and
back facing nozzles. This will ensure that the product is applied to the
grain head rather than the leaves or the ground.

--Hillary Mehl, Extension Plant Pathologist, Virginia Tech

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



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