Stripe rust (yellow rust or glume rust) has occurred (unpublished)
in Washington since the early 1900s; it became a major disease
on wheat in the late 1950s. The epidemic resulted from several
factors which coincided. A susceptible cultivar, 'Omar,' was
widely grown, and a series of open, mild winters aided the survival
of the rust on infected plant tissue. Unusually cool, wet springs
enhanced early season spread. Also, 'Omar' wheat planted as a
ground cover in the orchards of the Dalles was suspected to provide
inoculum to areas farther north. Development of the resistant
cultivar, 'Gaines,' was an important factor in stopping the epidemic.
Stripe rust is the most damaging of three cereal rusts occurring
in Washington. It can develop at lower temperatures than the
other rusts (Figure 5) and, therefore, can increase earlier in
the spring and act upon the host for a longer period of time.
Stripe rust is caused by Puccinia striiformis (synonym
P. glumarum). A number of pathogenic races occur and continue
to form as new cultivars are released. The fungus, a basidiomycete,
produces round, yellow-orange urediospores that have thick, spiny
walls and 6 to 12 scattered germ pores. Telia develop but have
no apparent function.
In the United States, wheat is the only host of consequence,
but barley and some perennial grasses may also become infected.
The aecial host is not known.
Symptoms and Signs
As is the case with most rust diseases, symptom development parallels
developmental stages of the causal fungus. The first sign is
the appearance of small, yellow, elongated uredial pustules in
rows on the leaf (Photo 9). These rows resemble sewing machine
stitches. When the pustules mature, they break open to release
a yellow-orange mass of urediospores. In many varieties, the
pustules develop in long, narrow, yellow stripes on leaves, leaf
sheaths and heads. Once infected plants mature or become stressed,
the tissue becomes brown and dry, and plants have a scorched,
Urediospores perpetuate the fungus on green host tissue, such
as volunteer wheat or susceptible wheat growing in other fields.
Urediospores lose their viability rapidly at temperatures above
59F. Germination is best between 41 and 59F, with limits at 32
and 68F. Infection may occur through the winter, since the mycelium
remains viable to 23F. The disease develops most rapidly between
50 and 59 F when intermittent rain or dew occurs. Many disease
cycles may take place in one season, since the time between infection
and sporulation under optimal conditions is about 8 days. Cool,
wet falls; mild, open winters; and long, cool, wet springs favor
Chemical. Certain systemic fungicides can interrupt
epidemic outbreaks. Timing is a critical and elusive consideration.
Early application may stop an outbreak if cool, wet weather does
not follow. If you apply fungicides too early, enough late infection
may occur to cause serious losses. Because of the fungicide cost,
it may be worthwhile to consider a split application. A second
spray would add only the application cost; moreover, if the second
application is not needed, you save both material and application
A predictive model has been developed to forecast occurrence
of stripe rust and need for fungicidal sprays. This model is
based on the fact that mild winters and springs favor stripe
rust development. It uses a base temperature of 7C (44.6F), the
optimum temperature for urediospore germination and infection
of the wheat plant.
Calculate degree days by subtracting 7 from the temperature
for each day. Given a temperature of 10C there would be three
positive degrees for that day; at 4C count three negative degrees.
Accumulate negative values for the coldest period (December 1
through January 31) and positive values for the spring period
(April 1 through June 30). If negative degree days total less
than 500, or if positive degree days total less than 440, there
is a high probability of severe rust. In other words, the milder
the winter and spring season, the greater the chance of rust.
Use this method with other considerations, such as cultivar planted,
relative susceptibility, date of seeding, and presence of rust
in the fall.
Resistance. Use of resistant cultivars has become
the major means of controlling stripe rust. Most of the resistance
develops in the mature or adult plant (MS or MR in Table 4).
Cultivars with this resistance are still susceptible in the seedling
stages. Cool weather during the growing season can delay development
of adult plant resistance.
In some wheats, resistance is of a specific type which is
effective at all stages of plant growth (R in Table 4), barring
development of a race of rust that can attack that resistance
type. However, when a pathogenic race develops that can overcome
the specific resistance, all cultivars bearing the same gene
for resistance are vulnerable. To circumvent this possibility,
wheat breeders use multilines, which are physical mixtures of
disease resistant genotypes. If a race arises that can attack
one of the components of the multiline, the genotype can be replaced
in future plantings by one that is resistant.
Table 4. Resistance to stripe rust and leaf rust in Leaf
rust selected Washington wheat varieties. a Adapted from the
1985 ratings of the Washington State Crop Improvement Association.
S = Susceptible;seedlings, adult plants,
and heads susceptible.
MS = Moderately susceptibel; seedlings
and head susceptible. Adult plants moderately resistant.
MR = Moderately Resistant; seedlings and
heads susceptible. Adult plants resistant.
R = Resistant; seedlings, head and adult
Coakley, S.M., R.F. Line, and L.R. McDaniel. 1988. Predicting
stripe rust severity on winter wheat using an improved method
for analyzing meteorological and rust data. Phytopathology 78:543-550.
Qayoum, A., and R.F. Line. 1985. High-temperature adult-plant
resistance to stripe rust of wheat. Phytopathology 75:1121-1125.
Other Interesting Stripe
UC Pest Management Guidelines, STRIPE
RUST -- Descriptions and pictures.
Agriculture, Food and Rural Development. Descriptions and
pictures of all the cereal rusts.
Diseases * Barley
Home Page * Small
Grains Home * Grow Serve
Edited and reviewed by Ed Adams, WSU Extension Plant Pathologist
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