Download pub3253powderymildewofwheat

Powdery Mildew of Wheat
Erysiphe graminis DC. f. sp. tritici Em. Marchal
Powdery mildew is not a major problem of wheat
in Louisiana. In limited cases, however, the disease can
reduce plant vigor, cause lodging and reduce yield, size of
kernels and test weight.
The fungus prevents plants from using nutrients,
reduces photosynthesis and increases both the
respiration and water loss (transpiration). In areas
where powdery mildew is severe, losses up to 40
percent have occurred. Heavily infected leaves, and even
entire plants, may be killed prematurely.
Damage is most severe when heavy infection occurs
during periods of rapid growth, tillering, stem elongation
and head development. Powdery mildew is associated
with dense plant growth and cool, moist conditions.
Mildew is most severe on wheat grown in soils with
a high nitrogen content. Excessive nitrogen fertilizer
that results in dense growth of plants creates ideal
environmental conditions for disease development.
Figure 2. Powdery mildew field symptoms
Powdery mildew is characterized by a white to
light gray, powdery fungal growth on the leaves, leaf
sheaths, culms and floral bracts. The lower leaves may be
completely covered.
Powdery mildew effectively is managed by growing
mildew-resistant varieties. Crop rotation, deep plowing
and the destruction of volunteer wheat will reduce the
chances of severe infection by removing or avoiding
overwintering sources of the fungus. Maintain balanced
soil fertility, based on a soil test, to avoid conditions in
which the fungus thrives – excessive nitrogen in relation
to phosphorus and potassium. Fungicide sprays rarely
are justified.
Figure 1.Typical powdery mildew symptoms
Authors:
Clayton A. Hollier, Ph.D., Professor
Department of Plant Pathology and Crop Physiology
Guy B. Padgett, Ph.D., Professor
Macon Ridge Research Station
Don Groth, Ph.D., Professor
Rice Research Station
Visit our website: www.LSUAgCenter.com
Louisiana State University Agricultural Center
William B. Richardson, Chancellor
Louisiana Agricultural Experiment Station
John S. Russin,Vice Chancellor and Director
Louisiana Cooperative Extension Service
Paul D. Coreil,Vice Chancellor and Director
Pub. 3253
(online only)
1/13
The LSU AgCenter is a statewide campus of the LSU System
and provides equal opportunities in programs and employment.