Powdery mildew beginning to appear on wheat
Editor’s note: This article is from the archives of the MSU Crop Advisory Team
Alerts. Check the label of any pesticide referenced to ensure your use is
included.
Powdery
mildew is beginning to show up on wheat in Michigan. Wheat is currently
at Feekes 5 around Isabella County, and at Feekes 6-7 (first to second
node) for most other parts of the state. It is not uncommon to see
powdery mildew low in the canopy, early in the season. Current
temperatures are in the favorable range (around 59-72°F) for this
disease. Often, mildew stays low in the canopy and does not cause
significant loss to yield. Powdery mildew is more of a concern if it
continues to climb and gets up on the flag leaf. If you are seeing it
now, continue to monitor your fields and evaluate the level of infection
at flag leaf to the boot stage. In general, the threshold for fungicide
treatment is two to three powdery mildew spots per leaf on the leaf
just below the flag leaf, (averaged over 30-50 leaves sampled randomly
in the field).
In the April 26 Field Crop CAT Alert, Management of foliar wheat disease, Part 2,
is a rating table of fungicides evaluated for effectiveness against
powdery mildew, and the growth stage limitations for applying certain
fungicides. You can check the MSU variety trials ratings (http://www.css.msu.edu/varietytrials/)
to get an idea of how your variety performed in statewide university
trials, and use your own field experience with a variety to determine
how susceptible it is to mildew. The variety trial ratings for powdery
mildew are scored from 0-9, with (0 the lowest amount of mildew, to 9
the highest) There is a yearly, two year, and three year average score.
Looking at the average rating over several years will give you a better
idea of performance than looking at a single year.