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May 7, 2004
Dean
Malvick
The
Bulletin - University of
Illinois
Stripe rust
of wheat is appearing in
Illinois
wheat fields. Robert Bellm, Extension educator from the
Edwardsville Extension Center, observed minor stripe rust in
wheat near
Lebanon.
Stripe rust is one of several foliar fungal diseases to watch
for now in wheat fields. Others include Septoria leaf blotch and
powdery mildew. As reported in the Bulletin 2 weeks ago (issue
no. 5, April 23, 2004), Fusarium head blight is also a
problem to watch for when wheat begins to flower.
Stripe rust
(also called yellow rust) of wheat often appears earlier in the
season than leaf rust. Stripe and leaf rusts are distinguished
by the color and pattern of the pustules. The stripe rust
pustules are more yellow to orange than rusty brown in color,
and they usually appear arranged in yellow stripes parallel to
veins on leaves. The pustules of leaf rust are dark to light
red/brown in color and are scattered in an arbitrary pattern
over the leaves.
Stripe rust of wheat in
Illinois
(2003). (Photo courtesy of Kevin Black.)
Stripe rust
can spread and reach damaging levels quickly when cool and moist
weather occurs, which favors development of the disease. Stripe
rust of wheat seems to have been spreading north more than usual
in the past few years. In 2003, it was fairly common and
widespread in
Illinois,
though mostly at low severity levels. Although stripe rust can
reach epidemic levels in wheat fields, it has been limited in
spread and development in Illinois, in part by weather that is
typically too warm and/or dry for the disease. Stripe rust
develops most rapidly when there is frequent dew or rainfall and
temperatures are between 50 and 60°F; it slows considerably when
temperatures exceed about 60 to 65°F at night and 70 to 75°F in
the day. The effect of temperature can vary with race of the
stripe rust fungus (Puccinia striiformis) and variety of
wheat in a field.
Stripe rust
can be managed with fungicides and to some degree with wheat
varieties that differ in susceptibility. Some of the fungicides
labeled for control of stripe rust include Tilt, PropiMax,
Quadris, Quilt, Headline, and Stratego. These products cannot be
applied after flowering (Feekes growth stage 10.5), and some
cannot be applied after the ligule of the flag leaf emerges
(Feekes growth stage 8). If fungicide application may be
warranted, consult the product labels prior to selection and
application of fungicides.
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