[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 10:51:58 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
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