CEREAL RUST BULLETIN
Final Report
August 5, 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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__________________________________________________________________
€ Only trace amounts of stem rust developed over most of the U.S.
in 1997.
€ Wheat leaf rust was wide spread with yield losses of 3% or more
in winter wheat from Oklahoma to South Dakota.
€ Several new races of wheat leaf rust appeared in the southern
Great Plains in 1997, putting resistance of some cultivars at
risk.
€ Oat crown rust in the north central states was less severe in
1997 than in 1996, partly because of limited infection on
buckthorn.
€ Barley stripe rust was severe in the Pacific Northwest for the
third consecutive year.
__________________________________________________________________
Most of the small grains in the northern Great Plains are in good
condition and near normal in plant maturity. Barley, oat and
winter wheat harvest has begun in southeastern North Dakota and
northeastern Montana.
Wheat stem rust
This year, wheat stem rust was found scattered in plots and fields
throughout the lower Mississippi Valley wheat-growing area. In
all of these areas, losses to wheat stem rust were light, but
these fields did provide stem rust inoculum for susceptible wheats
and barleys farther north.
During 1997, wheat stem rust overwintering sites were found in
late April in central and east central Louisiana. For example,
stem rust foci were scattered throughout a 40-acre field of CK
9835, while in varietal plots 60 miles away, the rust was so
severe that much of the wheat in some plots was killed by stem
rust. These sites in Louisiana were the only locations where
wheat stem rust was found during rust surveys through the
southeastern U.S., southern Oklahoma and northern Texas in the
last week of April. This year no stem rust overwintering sites
were found in south Texas, and in early May only traces of stem
rust were reported in central Texas varietal plots. Stem rust
development in Texas this year was less than normal.
In late May, traces of wheat stem rust were found in plots in
northeastern Louisiana and northwestern Arkansas. During the
second week in June, wheat stem rust foci one meter in diameter
were found in southeastern Illinois and northwestern Kentucky
fields. The next report of wheat stem rust in the soft red winter
wheat area was in early July, in a nursery in south central
Virginia.
In mid-July, traces of wheat stem rust were found in east central
South Dakota check plots of highly susceptible spring wheat
cultivars such as Morocco, and by the fourth week in July 40%
severities were observed in other susceptible spring wheat lines.
In mid-July, traces of stem rust were found in a plot of the
susceptible spring wheat Max in east central North Dakota. The
infections on Max were on the leaf sheaths and originated from
spores that were rain deposited 7 and 14 days earlier. The stem
rust infections in the northern plains this year may have
originated from rust spores that were released from rusted soft
red winter wheat fields in southern Illinois or the Ohio Valley
area. No other potential sources of wheat stem rust spores were
known to have existed at the time those infections occurred. This
year there were few reports of stem rust in fields and nurseries
and the number of stem rust collections received at the Cereal
Rust Lab were 1/4 of normal.
Several factors delayed stem rust development in the northern
plains: First, little stem rust overwintered in the southern
U.S., second, hot dry weather in June limited infection, and
third, stem rust resistance in the spring wheats remains highly
effective in the northern Great Plains.
In mid-July, small foci of stem rust were found on winter wheat
cultivars in the Palouse region of the Pacific Northwest. In late
July, in late maturing cultivars like Eltan, stem rust was severe
and will cause yield losses. Stem rust was severe in a few of the
susceptible spring wheat cultivars in eastern Washington and
northern Idaho and will cause lower grain weights in some fields.
To date, race Pgt-TPMK has been the only wheat stem rust race
identified in 1997. Stem rust identifications were made from
Arkansas, Illinois, Kentucky, Louisiana and Texas collections.
This is the first time in the past 79 years that only one stem
rust race has been identified from the U.S. rust collections.
Wheat leaf rust
Southern Plains - More leaf rust overwintered in the southern
Great Plains this year than last year. In late November, leaf
rust was found in many locations in Oklahoma and Texas. In mid-
March, wheat leaf rust was heavier than normal in plots and fields
of susceptible soft and hard wheats throughout southern and
central Texas. By late March, leaf rust was unusually heavy in
Oklahoma where it survived the winter (Fig. 1). During the first
week in April, 60% wheat leaf rust severities were observed on
lower leaves of susceptible cultivars in fields and nursery plots
throughout southern and central Texas. Cool, wet conditions in
many parts of Texas and Oklahoma during mid-April created good
conditions for rust increase. In mid-April, 80% severities were
reported on flag leaves of TAM 200, TAM 107 and 2163 at the
central Texas nurseries. Leaf rust was more severe in the central
Texas nurseries at McGregor and Temple than at the two southern
nurseries, Beeville and Uvalde. In some fields of susceptible
cultivars in central Texas, 40% severities were observed on the
upper leaves at the soft dough stage, and losses to leaf rust
occurred in these fields. During the last week in April, wheat
leaf rust severities in north central Texas and southern Oklahoma
fields ranged from trace to 2%, and in plots severities ranged
from trace to 40%. Most commercial cultivars in Texas expressed
susceptible reactions to leaf rust this year, which suggested that
there were new races in the area. The preliminary wheat leaf rust
race identifications in Table 1 has confirmed there has been a
change in the race population of Texas this year. Resistance of
the cultivars Big Dawg, Longhorn and Tomahawk held up fairly well.
During the third week of May in north central Oklahoma, 60% wheat
leaf rust severities were observed on the flag leaves of many of
the cultivars growing in fields and plots. In north central
Oklahoma varietal plots, cultivars like Karl 92, 2163 and Chisholm
had 60% severity readings, while rust severities in cultivars like
Custer, Jagger and 2137 were less than 5%. Estimated rust losses
to leaf rust in Oklahoma this year were near 10%.
In mid-May, 20% leaf rust severity readings were observed on
Triticum cylindricum (goatgrass) in western Oklahoma. This was
the heaviest leaf rust observed on goatgrass in the last five
years.
Central Plains - In mid-March, overwintered leaf rust was found in
the southern tier of Kansas counties. In early April, where leaf
rust overwintered in Kansas, rust pustules were found on the
lowest leaves, and farther north in Kansas rust was found on the
top two leaves. On April 12 and 13 in Kansas, frost damaged the
head and stem but did not destroy all of the rust-infected leaves.
Leaf development was set back somewhat by the freeze, but enough
leaf rust still survived to cause significant losses in Kansas and
provided inoculum for the wheat-growing areas farther north. In
late April, leaf rust was found on flag leaves in extreme southern
Kansas and rust progress was developing slower than expected
because of the cool weather.
Leaf rust was found on flag leaves of wheat in the southern tier
of counties of Kansas (excluding the far southwest) early in May.
By mid-May, leaf rust severity on flag leaves in south central
Kansas was as high as 40% in some fields of susceptible winter
wheat cultivars. In plots in the same area, severities on the
flag leaves ranged from 0 to 60%. In mid-May, leaf rust was also
found on flag leaves throughout central and northern Kansas, but
in those areas there was little rust on the lower leaves. The
lack of rust on lower leaves indicates that the flag leaf
infections came from spore showers from outside the region. From
the timing of the infection, it appears that Texas was the most
likely source of the spores. Leaf rust that overwintered on lower
leaves of wheat in southern Kansas was slow to develop due to the
cooler than normal night temperatures. In southern Kansas, the
rust was late in moving to the flag leaves from which it could be
spread farther north by wind. In mid-May, wheat in the west and
south central areas of the state was under moisture stress.
Overall, leaf rust was developing more slowly than expected. In
late May, in south central Kansas fields, 80% leaf rust severities
were common on the flag leaves of susceptible winter wheat
cultivars where rust overwintered. In varietal plots in south
central Kansas, leaf rust decimated most of the cultivars and the
only cultivar showing some resistance was Big Dawg. Throughout
northern Kansas, leaf rust development was slow. The cooler than
normal night temperatures during the last part of May may have
been one of the reasons why rust did not develop as fast as
expected. By the second week in June, 10% leaf rust severities
were observed in wheat fields in north central Kansas at soft
dough. The estimated loss due to leaf rust in Kansas is 3.7%.
In late May, traces of leaf rust were observed in plots and fields
in southern Nebraska. By the second week in June, 10% leaf rust
severities were observed in wheat fields in south central Nebraska
(Fig. 1). In early June, traces of leaf rust were observed on
lower leaves of wheat in eastern Colorado. In late June, leaf
rust severities ranged from trace to 80% on cultivars in south and
west central Nebraska varietal plots. In southern Nebraska fields
of susceptible cultivars, losses to leaf rust averaged around 5%.
Northern Plains - On June 2, trace amounts of leaf rust were found
in south central and southeastern North Dakota winter wheat plots.
Initial leaf rust development in the northern plains comes mainly
from windborne spores from the south that are deposited with rains
on wheat plots and fields in the north. During the second week in
June, traces of leaf rust were found in southeastern South Dakota
fields and varietal plots and in winter wheat varietal plots in
east central Minnesota. Fields of susceptible winter wheat in
central South Dakota had 50% to 80% leaf rust severities on flag
leaves during the first week in July (Fig. 1). During the second
week in July, 60% severities were observed in fields of winter
wheat at the mid-dough stage in southeastern North Dakota. Losses
to leaf rust in winter wheat in South Dakota could be as high as
10%, according to preliminary estimates. The rust infections in
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. Fields
of spring wheat in eastern South Dakota and North Dakota had only
traces of leaf rust due to their moderate to high levels of
resistance to prevailing races. Although most of the spring wheat
cultivars in the northern plains are resistant to leaf rust, some
cases of higher than usual leaf rust severities have been
reported. During mid-July, in west central Minnesota and
southeastern North Dakota, trace to 40% leaf rust severities were
observed on flag leaves of commercial spring wheat cultivars in
the late berry stage. In late July, trace to 10% severities were
reported on spring wheat in northern North Dakota and northwestern
Minnesota fields. Only light losses are expected, and most of
those losses will be in late planted fields. In plots of
susceptible spring wheats in west central Minnesota, east central
South Dakota, and east central north Dakota, 60% leaf rust
severities were reported on flag leaves in mid-July. As in South
Dakota, some yield losses from leaf rust are expected in winter
wheat in North Dakota. No rust was reported on durum wheat.
Southeast - In the southeast U.S., in late March, wheat leaf rust
was severe in plots and fields of susceptible soft red winter
wheat cultivars (Fig. 1). Leaf rust in the Southeast was much
more severe than last year in early spring. The winter rainfall
in southeastern U.S. was normal, creating favorable conditions for
rust infection. In southern Louisiana, in early April, many of
the cultivars that previously were resistant were showing
significant rust development this year. During the last week in
April, 60% severities on flag leaves were observed in plots and
fields of susceptible soft red winter cultivars in the
southeastern U.S. In southern Arkansas, during early May, leaf
rust development on flag leaves was severe in many late-planted
fields of susceptible cultivars. Cultivars most affected were
Wakefield, Hazen, Jackson, Coker 9803, Hickory and Pioneer 2580.
While the leaf rust epidemic in southern Arkansas was too late to
cause major damage to the whole wheat crop, this is the most
significant rust problem in several years in the state and caused
damage in late-maturing fields. In late May, wheat leaf rust was
severe in varietal plots and light in fields in the bootheel of
Missouri, northeastern Arkansas and western Tennessee. Wheat leaf
rust pustules were found on flag leaves during the first week in
May in the coastal plain of South Carolina,. In mid-May, in the
coastal plain of South Carolina, wheat leaf rust caused premature
senescence of the state¹s predominant cultivar (Coker 9835).
Midwest - During the second week in June, trace leaf rust ratings
were recorded on most of the wheat cultivars in southern Indiana
plots, while 20% severities were recorded on a few susceptible
lines. By early June, traces of leaf rust were reported in soft
red winter wheat fields in southeastern Wisconsin, south central
Michigan and northwestern Indiana. Losses will be light in this
area since the rust was light and developed later than normal.
California - Leaf rust was light in wheat fields in the San
Joaquin Valley during the third week in April and by late April,
leaf rust was found throughout the Sacramento Valley fields.
Since wheat leaf rust developed so late, rust losses were light
throughout the state.
Northwest - In late May, wheat leaf rust was light in the Skagit
Valley of western Washington. In early June, in eastern
Washington, 1-2% severities were reported in some fields and leaf
rust was also increasing in the Willamette Valley of western
Oregon. 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. Most
of the spring wheat cultivars have adequate adult plant resistance
to combat the rust. In late July, wheat leaf rust was increasing
in spring wheat fields in the Palouse region of Washington and
will decrease yields in late maturing susceptible wheat.
Northeast - By late May, in varietal plots in eastern Virginia,
wheat leaf rust severities ranged from 10 to 50%. In mid-June,
leaf rust was light in winter wheat fields in south central
Pennsylvania. 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. Losses to leaf rust were very minimal in
the northeastern U.S. in 1997.
The wheat leaf rust races identified so far in the 1997 survey are
presented in Table 1. Race MBRL, which is virulent to
Lr1,3,3ka,10,11,30, is the most commonly identified race this year
and also was the most common race for the last four years. So
far, 20 races have been identified in Texas this year and of
these, 4 were not identified in previous Texas surveys. Some
races like MBNL, MBTL and MFDL have Lr 17 as part of their
virulence package. Lr17 is part of the leaf rust resistance in
Jagger which has been and will be grown on a large part of hard
red winter wheat acreage next year.
TABLE 1. Wheat leaf rust races identified through July 31, 1997
______________________________________________________________
PRT Number of isolates by state
code Virulence formula1 AL AR CA FL GA KS LA MS OK TX
______________________________________________________________
CBGB 3,11 2
MBBB 1,3 1
MBBL 1,3,10 1 1 3
MBBQ 1,3,10,18 9
MBDL 1,3,10,17 1
MBGL 1,3,10,11 2 1
MBGQ 1,3,10,11,18 2
MBNL 1,3,3ka,10,17 4
MBRL 1,3,3ka,10,11,30 14 12 5 3 4 1 10
MBRQ 1,3,3ka,10,11,18,30 6 2 2 4 16 3 1
MBTL 1,3,3ka,10,11,17,30 1
MCBL 1,3,10,26 2
MCBQ 1,3,10,18,26 2
MCDL 1,3,10,17,26 17
MCJL 1,3,10,11,17,26 1
MCRL 1,3,3ka,10,11,26,30 3
MCRQ 1,3,3ka,10,11,18,26,30 5 5 3 9 1
MCTL 1,3,3ka,10,11,17,26,30 2
MDBL 1,3,10,24 2 2 6
MDGL 1,3,10,11,24 2 1
MDRL 1,3,3ka,10,11,24,30 8 1 13
MDRQ 1,3,3ka,10,11,18,24,30 1 8 3
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 1 2
TDBL 1,2a,2c,3,10,24 1 2 1 12
TDRL 1,2a,2c,3,3ka,10,11,24,30 1 3
TFCL 1,2a,2c,3,10,24,26,30 1
TFBL 1,2a,2c,3,10,24,26 2 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 2 4 2
Number of isolates 43 25 16 8 18 20 33 4 8 88
Number of collections 26 13 8 4 12 11 17 2 5 49
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1 Single gene resistances evaluated:
Lr1,2a,2c,3,3ka,9,10,11,16,17,18,24,26,30
Wheat stripe rust
During late April, stripe rust was first found in the south
central U.S. in a 50-acre field of Mason in northeastern
Louisiana. The rust was severe and was found throughout the whole
field. In mid-May in Arkansas, south of I-40, stripe rust was
still active in many wheat fields because of the cool
temperatures. Fungicides were sprayed in some fields to control
the rust. In late May, traces of stripe rust were found in wheat
fields in the bootheel of Missouri and western Tennessee.
Generally, every year stripe rust is found in a few locations
along the southern Mississippi Valley.
During the third week in March, wheat stripe rust was observed in
California on a new variety, UC 1041, in the Yolo county plots and
in the Davis campus nursery. By the second week in April,
moderate stripe rust severities were reported in the San Joaquin
Valley and traces were found in the Sacramento Valley of
California. During the last week in April, in the Sacramento
Valley of California, wheat stripe rust foci were found in fields
of the fall-sown hard red spring wheat cultivar Express. During
early May, traces of wheat stripe rust were found in wheat fields
in the Sacramento Valley. Several entries in statewide hard red
spring wheat nurseries showed susceptible reactions. There may be
a race change occurring in California where wheat stripe rust
appeared on cultivars which have had effective resistance since
the mid-70s.
In late April, wheat stripe rust was observed in nursery plots in
the Skagit Valley of western Washington on the lower leaves (20%)
but not on the upper leaves. In late April, in the area west of
Pascoe, stripe rust hot spots were found and rust became a problem
in this area because crop maturity was delayed due to the cold
spring. During the second week in June, stripe rust was very
severe on many wheat cultivars in the Skagit Valley of western
Washington. 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 mid-May,
stripe rust was increasing in central Washington on hard red
winter and club wheats. In mid-June, in the Palouse area of
Washington, stripe rust ratings of 10-20% were found in wheat
fields. In early July, wheat stripe rust was severe on
susceptible winter wheat cultivars in the Palouse region of
eastern Washington and northern Idaho, and in mid-July,wheat
stripe was increasing in spring wheat fields in the Palouse
region, 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 because of good moisture
conditions and cool weather.
Oat stem rust
In mid-February, traces of oat stem rust were found in the nursery
plots at Beeville in southern Texas. During the first week in
April, hot spots of oat stem rust 0.5 m in diameter were found in
southern Texas fields and nursery plots. Along the roadside in
central Texas, traces of stem rust were observed on wild oat
(Avena fatua). The rains during the first week in April were good
for rust infection and the rust increased significantly. During
the second week in May, oat stem rust was increasing rapidly in
varietal plots in College Station. The Texas oat stem rust
provided inoculum for areas farther north, but the lack of oat
acreage in the central Great Plains tended to interrupt potential
epidemics.
This year, by late March, stem rust was increasing in oat varietal
plots in southern Louisiana where it generally can be found every
year by early March. During the second week in April, 50% oat
stem rust severities were observed in varietal trial plots in
southwestern Alabama. During the last week in April,
overwintering centers of stem rust were found in an oat field in
east central Louisiana and in oat varietal plots in southern
Georgia, southwestern Alabama, southwestern Mississippi and
central Louisiana. Severe oat stem rust was found in varietal
plots and fields throughout central and northeastern Louisiana by
mid-May. These locations provided oat stem rust inoculum for
areas farther north.
In early May, oat stem rust was found in plots in the Sacramento
Valley of California.
In mid-July, traces of oat stem rust were found in plots in east
central South Dakota, central, and west central Minnesota. These
were the first reports of oat stem rust in the U.S. since mid-May,
when oat stem rust was found in fields and plots in Texas,
Louisiana and Alabama. Much less oat stem rust has been found in
the northern Great Plains the past three years than in previous
years. The reduced amount of oat stem rust seems to be associated
with a decline in oat production.
Race NA-27, virulent to Pg-1,2,3,4, and 8 remains the predominant
race of the oat stem rust population (Table 2).
TABLE 2. Oat stem rust races identified through July 31, 1997
__________________________________________________________________
Number of Number of isolates per state
State collections isolates NA-10 NA-16 NA-27
__________________________________________________________________
Alabama 3 9 9
California 2 6 6
Florida 4 12 12
Louisiana 5 15 7 8
Mississippi 2 6 3 3
Texas 13 35 35
Total 29 93 9 10 74
__________________________________________________________________
*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/1,3,8
Oat crown rust
By late February, crown rust was found in southern Texas plots and
the rust was much more severe this year than last year. During
the first week in April, crown rust was severe in southern and
central Texas fields and plots. Sixty-percent severities were
common on the most susceptible cultivars in nursery plots and in
some cultivars, the rust was killing the host. In some fields in
southern Texas, overwintering hot spots 3-m in diameter with
40-60% severities were observed. In late April, crown rust was
severe in central Texas varietal plots, while in oat fields,
severities were moderate(1-20%). The Texas oat crown rust
inoculum is available for areas farther north, but the lack of oat
acreage in the central Great Plains tends to interrupt potential
epidemics.
In late March, severe crown rust was found in varietal plots in
southern Louisiana. By mid-April, crown rust was severe (>80%) in
oat varietal plots and moderate (1-20%) in oat fields. In plots
in southwestern Alabama and central Louisiana, the rust was so
severe it killed some of the oats. This widespread crown rust
development is equal to the rust development of the last three
years in the southeastern U.S. Crown rust development in the
southeastern U.S. has provided inoculum for areas farther north.
In mid-June, traces of oat crown rust were found in oat fields in
west central Indiana.
Crown rust pycnia appeared on buckthorns in St. Paul, Minnesota,
on May 19. The infections apparently came from basidiospores
released from germinating teliospores on infected straw during
rains on May 7-8. Buckthorn bushes are the alternate host for
crown rust and generally provide the initial spores for crown rust
infections of the northern oat crop. In late May, aeciospores,
which can infect oat, were found on buckthorn leaves in southern
Minnesota and southern Wisconsin. In early June, moderate to
severe aecial infections were found on buckthorn bushes in south
central and southeastern Wisconsin. By June 17, 20% crown rust
severities were observed on lower leaves of oats growing near the
buckthorn bushes in the nursery on the University of Minnesota,
St. Paul campus. By the second week in June, traces of crown rust
were found in southern Wisconsin oat fields. Crown rust developed
slowly due to cool weather in the northern oat-growing area. 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. In early July, light levels of oat
crown rust were detected in a few fields in southern Minnesota,
central Wisconsin, and south central Pennsylvania. During mid-
July, crown rust severities ranged from trace to 10% in oat fields
and trace to 40% on flag leaves in plots in west central and
southern Wisconsin. In late July, oat crown rust severities
ranged from trace to 60% in plots and trace to 10% in fields in
northwestern Minnesota and northeastern North Dakota. The most
severe crown rust was found where rust occurred early and
conditions were conducive for rust development. Buckthorn growing
in close proximity to oat fields provided the initial inoculum in
these areas, i.e., southern Minnesota and southern Wisconsin.
In early June, aecial development was light on buckthorn bushes in
eastern South Dakota. In early July, 10% crown rust severities
were found on lower leaves of susceptible oat cultivars in eastern
South Dakota varietal plots. During mid-July, crown rust
severities ranged from trace to 5% in oat fields and trace to 40%
on flag leaves in plots in eastern South Dakota and east central
North Dakota. No crown rust was found in oat plots in central
South Dakota. Lack of moisture in May and cooler than normal
weather in early June delayed rust development, but warmer and
rainy weather than normal in early July favored crown rust
increase. Rainy weather, however, washed much of the inoculum off
infected plants before spores could spread. This was one of the
lowest levels of crown rust infections on buckthorn and oats in
recent years in South Dakota.
Losses to crown rust were less severe than last year in the
northern oat-growing area, with the latest planted fields
suffering the most damage.
The incidence of virulence for 1997 crown rust isolates tested to
date is presented in Table 3.
TABLE 3. Incidence of virulence in 1997 crown rust isolates
tested to date (7/31/97)
___________________________________________________________
Per cent isolates virulent
Differential TX LA FL,MS,AL,GA SC CA
___________________________________________________________
Pc14 91 89 88 73 86
Pc35 42 26 50 0 14
Pc36 2 68 44 82 43
Pc38 58 53 50 45 14
Pc39 48 42 38 9 43
Pc40 97 95 100 100 86
Pc45 12 5 25 0 86
Pc46 55 21 31 27 86
Pc48 9 0 19 0 57
Pc50 55 42 44 82 29
Pc51 97 74 5 9 29
Pc52 15 0 13 0 43
Pc53 0 0 0 0 0
Pc54 15 26 25 45 86
Pc55 45 42 31 9 43
Pc56 39 58 31 82 43
Pc57 45 16 6 0 43
Pc58 15 11 0 9 29
Pc59 30 37 19 0 14
Pc60 91 84 69 100 29
Pc61 76 89 100 100 29
Pc62 0 5 6 0 0
Pc63 36 32 25 9 14
Pc64 0 5 0 0 0
Pc67 36 68 13 73 57
Pc68 0 0 0 0 0
Pc70 55 37 44 36 29
Pc71 52 47 31 18 43
___________________________________________________________
Total 33 19 16 11 7
Barley stem rust
races of barley stem rust were first found this year on May 19 in
barley plots in south Texas at Beeville. Limited amounts of
barley are grown commercially in the southern states and stem rust
on barley rarely occurs in this area. In mid-July, traces of
barley stem rust were found on spring barleys in east central
South Dakota plots. Less barley stem rust was found in the
northern plains this year because nearly all barley cultivars are
resistant to wheat stem rust race TPMK. Race QCCJ, which infects
barley cultivars with the resistance gene Rpg 1, was not found in
the southern U.S.
Barley leaf rust
During the first week in April, trace to 10% leaf rust severities
were observed on lower leaves of barley in southern and central
Texas plots.
In late May, light amounts of barley leaf rust were reported in
south central Pennsylvania and in the Skagit Valley of western
Washington on winter barleys. By the second week in June, barley
leaf rust was moderate to severe, and in early July, it was severe
on susceptible fall-planted and spring-planted cultivars in
varietal plots in the Skagit Valley.
In mid-July, trace - 40% barley leaf rust severities were observed
in barley plots in west central Minnesota and northeastern South
Dakota, but no leaf rust was found in fields.
This year, losses to barley leaf rust were light in the United
States.
Barley stripe rust
In early March, ³hot spots³ of barley stripe rust were observed
in nurseries and variety strip tests on the Davis, California
agronomy farm. By the first week of April, barley stripe rust was
severe on the Davis campus and Yolo county plots in California.
During the second week in April, barley stripe rust was present in
light to severe amounts in commercial fields in the San Joaquin
Valley of California. In some fields, the infections were lighter
than 1996, but in other fields, 20% severities were observed on
flag leaves. It was observed that even under dry conditions,
barley stripe rust increased. During late April, barley stripe
rust was widespread in California¹s fall-sown spring barley crop.
Some advanced lines that tested resistant last season are
susceptible this season. Many of the commercial cultivars are
extremely susceptible, while UC 603 exhibits a high level of
tolerance. By early July, stripe rust on barley was appearing on
spring-sown barley in the intermountain area of northeastern
California. Eighty to 100% severities were reported in
northeastern California nurseries, and in commercial fields, 100%
severities were reported on flag leaves at the milk growth stage,
which may lead to a 50% or more loss in yield. Many fields in
this area were being sprayed with Folicur in order to control the
rust. Except for northeastern California, total crop damage will
be less than in 1996, since stripe rust onset was late this
season, while crop development was earlier.
In early March, barley stripe rust was found in winter barley
plots at Corvallis, Oregon. By late March, stripe rust pustules
were found at low levels in susceptible varieties within a 16-m
diameter circle of the original infected plots, and by mid-April,
barley was heavily infected with stripe rust in winter trial plots
at Corvallis. During the last two weeks in April, cool, wet
weather slowed stripe rust development in winter barley plots, but
in late May, barley stripe rust was increasing in spring barley
plots at Corvallis.
In late April, 20% stripe rust severities were reported on lower
leaves of barley, and by late May, stripe rust was severe on
susceptible winter cultivars growing in the Skagit Valley of
western Washington. 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.
In early July, light amounts of barley stripe rust were detected
in the Palouse region of the Pacific Northwest.
In mid-July, 70% severities were observed in spring barley test
plots in west central Idaho and traces in the northern tip of
Idaho. Since the plants were in an advanced plant growth stage,
the rust should not significantly affect the yield.
Barley stripe rust is now firmly established in California and the
Pacific Northwest, where the climate is most favorable for its
development. Losses to barley stripe rust occurred in fields
throughout California and the Pacific Northwest.
Crown rust on barley
During the second week in July, 20% crown rust severities were
observed in barley growing 15 meters from Rhamnus bushes in east
central North Dakota. Barley crown rust was found in commercial
fields throughout the Red River Valley. Crown rust reached 80%
severity on susceptible barley cultivars planted in an east
central South Dakota nursery. Light losses to barley crown rust
occurred in barley fields growing in close proximity to Rhamnus
bushes.
Rye stem rust
In late July, traces of rye stem rust were found in plots in
central Minnesota.
Rye leaf rust
During the first week in April, 40% leaf rust severities were
observed on the flag leaf in winter rye plots in central Texas.
By the last week in April, in central and north central Texas
plots, rye leaf rust severities ranged from 1-5% on the flag
leaves. Forty-percent leaf rust severities were observed on
winter rye in fields in north central Oklahoma on May 19.
In a field of rye in southern Alabama, 20% leaf rust severities
were observed on the flag leaves in late April. Rye leaf rust was
found in a nursery in Plains, Georgia on May 13.
In late June, 40% rye leaf rust severities were reported in a
plot in east central South Dakota. In late July, 5-50% rye leaf
rust severities were observed in spring rye plots in central
Minnesota and northeastern North Dakota.
Rye leaf rust was scattered throughout the U.S. in plots and
fields and losses will be light in 1997.
Stem rust on barberry
During mid-May, aecial development was observed on common barberry
(Berberis vulgaris) bushes (alternate host for stem rust) in south
central Wisconsin. During the second week in June, aecial
development was observed on barberry bushes in southeastern
Minnesota.
Rust on other grasses
During the first week in April, severe crown rust was observed on
ryegrass and severe leaf rust on little barley (Hordeum pusillum)
in southern Alabama and Louisiana. During the first week in July,
stem rust was found on quackgrass (Elytrigia repens) and redtop
(Agrostis alba), which were growing within 30 meters of the common
barberry in southeastern Minnesota.
This is the last issue of the Cereal Rust Bulletins for the
1996-97 growing season. I would like to thank all of those who
helped with the bulletin this year, especially Mark Hughes who
coordinates its distribution through the CRL web page
(http://www.crl.umn.edu), email (markh@puccini.crl.umn.edu) and
the post. As most universities and research facilities now have
access to the Internet, we would like to use this system for
exchanging information. Any reports of rust that you find in your
area will be appreciated and this information will be added to the
CRB and possibly our web page. My username is
davidl@puccini.crl.umn.edu.
- David Long