CEREAL RUST BULLETIN
Report No. 7
July 8, 1997
Issued by:
CEREAL RUST LABORATORY
U.S. DEPARTMENT OF AGRICULTURE
AGRICULTURAL RESEARCH SERVICE
UNIVERSITY OF MINNESOTA
1551 Lindig St, ST. PAUL , MN 55108-6052
(612) 625-6299 FAX (612) 649-5054
Internet: markh@puccini.crl.umn.edu
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__________________________________________________________________
€ Wheat leaf rust is severe in South Dakota winter wheat fields.
€ Wheat stripe rust overwintering centers were found in the
Gallatin Valley of Montana.
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The small grain harvest has commenced from south central
Pennsylvania to southern Nebraska. Winter wheat is in good
condition throughout most of the U.S. In the northern small grain
area, most of the spring-sown grains are in good condition and
slightly behind normal crop development. Small grains are
generally in good condition in the main grain-growing area of the
Red River Valley.
Wheat stem rust
There have been no new reports of wheat stem rust since the last
bulletin. From the stem rust wheat collections made in late April
in central Louisiana, the TPMK race was identified. This has been
the most commonly identified race in most of the past 20 years.
Wheat leaf rust
In late June, leaf rust severities ranged from trace to 80% on
cultivars in south and west central Nebraska varietal plots.
Most of the cultivars in the south central Nebraska plots at North
Platte were rusted. We expect to identify many different leaf
rust races from these plots, because the cultivars have different
combinations of resistance genes.
Fields of susceptible winter wheat in south central South Dakota
had 50% to 80% leaf rust severities on flag leaves during the
first week in July (Fig. 1). Yield losses in winter wheat could
be as great as 10% in South Dakota according to preliminary
estimates. The rust infections in Nebraska and South Dakota
probably originated from spore inoculum sources in Oklahoma and
southern Kansas.
Varietal plots of susceptible spring wheat in east central South
Dakota had 50% to 80% leaf rust severities in early July.
Commercial cultivars of spring wheat in fields in eastern South
Dakota and North Dakota and central Wisconsin had only traces of
leaf rust due to their moderate to high levels of resistance to
prevailing races.
During the first week in July, light amounts of leaf rust were
found in winter wheat fields and plots in central and western New
York. In early July, wheat leaf rust was severe on susceptible fall
planted and spring planted cultivars growing in varietal plots in
the Skagit Valley in northwestern Washington and the Palouse
region of eastern Washington and northern Idaho. In commercial
fields in these areas, leaf rust developed late on the winter
wheat and will only cause slight damage to the crop and the spring
wheat cultivars have adequate adult plant resistance to combat the
rust. The preliminary leaf rust race identifications for 1997 are
shown in Table 1.
TABLE 1. Wheat leaf rust races identified through July 8, 1997
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Number of isolates by state
Prt
code Virulence formula* AL AR GA LA OK TX
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CBGB 3,11 2
MBBL 1,3,10 1 1
MBGL 1,3,10,11 2 1
MBNL 1,3,3ka,10,17 4
MBRL 1,3,3ka,10,11,30 10 12 5 4 10
MBRQ 1,3,3ka,10,11,18,30 3 2
MBTL 1,3,3ka,10,11,17,30 1
MCBL 1,3,10,26 2
MCDL 1,3,10,17,26 17
MCRL 1,3,3ka,10,11,26,30 3
MCRQ 1,3,3ka,10,11,18,26,30 2 1 1
MCTL 1,3,3ka,10,11,17,26,30 2
MDBL 1,3,10,24 6
MDGL 1,3,10,11,24 1
MDRL 1,3,3ka,10,11,24,30 4 13
MFBL 1,3,10,24,26 3 2
MFDL 1,3,10,17,24,26 1
MFRL 1,3,3ka,10,11,24,26,30 1
MFTL 1,3,3ka,10,11,17,24,26,30 1
PNMQ 1,2c,3,3ka,9,10,18,24,30 4 1
TBBL 1,2a,2c,3,10 1 2
TDBL 1,2a,2c,3,10,24 1 2 12
TDRL 1,2a,2c,3,3ka,10,11,24,30 3
TFCL 1,2a,2c,3,10,24,26,30 1
TFBL 1,2a,2c,3,10,24,26 2
TFGL 1,2a,2c,3,10,11,24,26 4
TGBL 1,2a,2c,3,10,16 1
TLGG 1,2a,2c,3,9,11,18 4
_________________________________________________________________
Number of isolates 23 18 18 7 2 88
Number of collections 12 9 11 4 1 49
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*Single gene resistances evaluated:
Lr1,2a,2c,3,3ka,9,10,11,16,17,18,24,26,30
Wheat stripe rust
During the first week in July, wheat stripe rust was severe on
susceptible fall planted and spring planted cultivars in
northwestern Washington nurseries, but since most of the
commercial cultivars in this region have good adult plant
resistance to stripe rust, losses will be light. In early July,
wheat stripe rust was severe on susceptible winter wheat cultivars
in the Palouse region of eastern Washington and northern Idaho,
but will not cause significant losses because the commercial soft
white winter and spring wheats have good adult plant resistance to
stripe rust.
In the first week in July, wheat stripe rust was found in
overwintering centers in the Gallatin Valley of Montana. The
stripe rust is expected to increase with good moisture conditions
and cool weather.
Oat stem rust
There have been no new reports of oat stem rust since the May 13
bulletin. The most commonly identified oat stem rust is NA-27,
which has been true in previous race surveys (Table 2).
TABLE 2. Oat stem rust races identified through July 7, 1997
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Number of Number of isolates per state
State collections isolates NA-10* NA-16 NA-27
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Alabama 3 9 9
California 1 3 3
Florida 4 12 12
Louisiana 4 12 4 8
Mississippi 2 6 3 3
Texas 10 29 29
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Total 24 71 3 7 61
*Virulence formula (Avirulence/Virulence):
NA-10 1,4,8,9,13,16,a/2,3,15
NA-16 2,4,9,13,15,16,a/1,3,8
NA-27 9,13,15,16,a/1,2,3,4,8
Oat crown rust
In early July, trace to light levels of oat crown rust were
detected in a few fields in north central Kansas, southern
Minnesota, central Wisconsin, and south central Pennsylvania.
Crown rust is developing slowly due to cool weather in the
northern plains.
By June 30, crown rust infection was severe (50-80%) on
susceptible oat cultivars near the buckthorn nursery on the
University of Minnesota, St. Paul campus. Cool weather over the
past week has delayed further buildup.
In early July, 10% severities were found on lower leaves of
susceptible oat cultivars in eastern South Dakota varietal plots.
TABLE 3. Incidence of virulence in 1997 crown rust isolates
tested to date (7/2/97)
Percent of isolates virulent
Differential GA,AL,MS LA TX CA
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Pc 14 89 86 90 67
Pc 35 22 21 43 17
Pc 36 11 57 24 17
Pc 38 44 43 57 17
Pc 39 0 29 43 17
Pc 40 100 93 95 67
Pc 45 0 7 10 67
Pc 46 11 21 57 67
Pc 48 11 0 0 33
Pc 50 22 36 52 0
Pc 51 33 64 100 17
Pc 52 0 0 5 17
Pc 53 0 0 0 0
Pc 54 0 14 10 67
Pc 55 0 29 38 17
Pc 56 11 57 24 17
Pc 57 22 14 48 50
Pc 58 0 0 5 17
Pc 59 0 36 29 17
Pc 60 67 79 86 17
Pc 61 100 93 76 17
Pc 62 0 7 0 0
Pc 63 0 21 38 17
Pc 64 0 7 0 0
Pc 67 0 57 24 50
Pc 68 0 0 0 0
Pc 70 0 36 48 17
Pc 71 0 36 48 17
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No. of isolates 9 14 21 6
Barley stem rust
There have been no new reports of barley stem rust since May 19th
when it was found in plots in south Texas.
Barley leaf rust
In early July, barley leaf rust was severe on susceptible fall
planted and spring planted cultivars growing in varietal plots in
the Skagit Valley of western Washington. The spring planted
barley cultivars are all susceptible to leaf rust.
Stripe rust on barley
By the first week in July, severe barley stripe rust was found on
susceptible fall planted and spring planted cultivars growing in
varietal plots in the Skagit Valley of western Washington. Light
amounts of barley stripe rust were detected in the Palouse region
of the Pacific Northwest.
Rye rusts
In late June, 40% rye leaf rust severities were reported in a
plot in east central South Dakota. No rye stem rust has been
reported in the U.S. this year.
Stem rust on barberry
There have been no new reports of stem rust on barberry since the
last bulletin.
Rust on other grasses
During the first week in July, stem rust was found on quackgrass
(Elytrigia repens) and redtop (Agrostis alba), that was growing
within 30 meters of the common barberry (Berberis vulgaris) in
southeastern Minnesota.
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