Cereal Rust Bulletin
Final Report
August 4, 1999
Issued by:
Cereal Disease Laboratory
U.S. Department of Agriculture
Agricultural Research Service
University of Minnesota
1551 Lindig St, St. Paul, MN 55108-6052
(612) 625-6299 FAX (651) 649-5054
markh@puccini.crl.umn.edu
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€ Stem rust was common on wheat, barley and oat in the northern
Great Plains.
€ Wheat leaf rust in the upper Midwest was more severe than in
the last 20 years.
€ Oat crown rust was lighter than normal throughout the upper
Midwest.
€ Barley stripe rust was light in the Pacific Northwest.
Wheat stem rust
In 1999, wheat stem rust severities were generally light in
varietal plots and fields throughout the southern U.S. During
mid-May, a few late maturing wheat varieties were heavily rusted
with stem rust in southern Louisiana nursery plots. In late May,
severe stem rust was observed during harvest on late maturing
susceptible wheats in central Texas wheat plots. Wheat stem rust
development was much lighter than normal in 1999 throughout the
southern U.S.
During the first week in June, stem rust foci were found on the
cultivar Mit, and traces of rust were found scattered on other
cultivars such as Onaga and 2174 in south central Kansas
nurseries. In mid-June, wheat stem rust was light on susceptible
cultivars, e.g., Onaga, throughout central and north central
Kansas plots. In late June, trace-10% severities of stem rust
were observed at the hard dough stage in north central Kansas and
south central Nebraska fields, but losses were negligible. Wheat
stem rust developed late in the Central Plains. Most of the
cultivars were early maturing and therefore escaped the stem rust.
The stem rust infected areas in the Central Plains provided spores
for susceptible wheats farther north.
In late June, foci of wheat stem rust, 1 meter in diameter at 10%
severity, were found in plots of the susceptible spring wheat
Baart in south central and west central Minnesota and in plots of
winter wheat cultivars, e.g., 2137, in central and east central
South Dakota. In much of the central and northern Great Plains,
the temperatures were near normal and moisture was ideal for the
spore infection process to occur. During the second week of July,
stem rust severities of 5- 80% were reported in a winter wheat field of 2137 in central South
Dakota. A significant yield loss to stem rust occurred in this
field. In other fields in central South Dakota, trace to 20%
severities were observed, but incidence was low. In mid-July,
trace to 20% severities were observed in winter wheat plots in
east central South Dakota and southeastern North Dakota. By mid-
July, check plots of highly susceptible spring wheat cultivars
such as Baart had 20% stem rust severities in south central
Minnesota and east central South Dakota and traces of stem rust
were found in southeastern North Dakota. In late July, 30%
severities were reported on Baart in north central North Dakota
plots.
Stem rust was unusually prevalent in the Northern Plains this
year. The number of stem rust samples received at the Cereal
Disease Lab this year was twice as great as in recent years. The
increased severity of stem rust in the Northern Plains can be
attributed to the large amount of inoculum produced on winter
wheat cultivars, e.g. 2137, farther south in the Central Plains,
and to the temperature and moisture, which were ideal for stem
rust infection in the Northern Plains this year. If current
spring wheat cultivars were susceptible to stem rust, a serious
epidemic with substantial yield losses would have occurred.
In mid-June, light stem rust was found in wheat plots in
southwestern Virginia.
To date, races Pgt-QCCJ, QCCS, QFCJ, QFCS, and RCRS have been
identified from collections made in the southern U.S. (Table 1).
The increased frequency of race QCCJ could represent a significant
race shift in the wheat stem rust population. The QCCJ race is
virulent on barley cultivars with the Rpg1 (T) gene for
resistance. RCRS was the most commonly identified race in 1998.
Table 1. Wheat stem rust races identified through July 30, 1999
______________________________________________________________
Number of isolates by state
____________________________
Race Virulence formula Texas Louisiana
______________________________________________________________
QCCJ 5,9d,9g,10,17,21 3 3
QCCS 5,9a,9d,9g,10,17,21 2
QFCJ 5,8a,9d,9g,10,17,21 1
QFCS 5,8a,9a,9d,9g,10,17,21 1
RCRS 5,7b,9a,9b,9d,9g,10,17,21,36 7
______________________________________________________________
Number of isolates 14 3
Number of collections 6 1
______________________________________________________________
Wheat leaf rust
Southern Plains - During mid-March, wheat leaf rust severities
ranged from traces on flag leaves to 60% on the lower leaves of
cultivars in nursery plots throughout southern Texas (Fig. 1).
For example, plots of Custer had traces of leaf rust, but Karl 92
had 60% severities. Commercial wheat fields in southern Texas had
rust severities ranging from traces to 20% on the lowest leaves.
In southern Texas, rust increased on the lower leaves when
moisture was abundant, but rust increase farther up the plant was
limited because of dry weather. In southern Texas, in early April,
leaf rust was severe on spring wheats like Norm (30%).
In central Texas during early April, leaf rust was much more
severe and widely distributed than normal in wheat fields and
plots. The mild winter and moist conditions in February and March
contributed to the rust development in much of this area. In mid-
April, leaf rust severities of 80% were observed in central Texas
plots of TAM-107. During the last week in April, wheat leaf rust
severities in north central Texas and southern Oklahoma ranged
from trace to 80% in plots, and in fields where rust overwintered,
severities were as high as 70% on flag leaves. Leaf rust was more
severe than last year in this area.
During November in Oklahoma, leaf rust was severe on some of the
commonly grown cultivars. However, a hard freeze in mid- to late
December, followed by dry conditions through January and early
February, eliminated this leaf rust in many of these fields. By
early March leaf rust was less severe, since most of the rusted
leaves died without the rust spreading to the younger leaves
because of the dry weather in February. In late March, moist
conditions allowed rust to increase and provided inoculum for the
wheat-growing areas farther north.
During the last week in April, wheat leaf rust severities in
southern Oklahoma ranged from trace to 80% in plots, and in fields
where rust overwintered, severities were as high as 70% on flag
leaves. Leaf rust is more severe than last year in this area.
These areas provided rust inoculum for wheat grown in Kansas and
Nebraska.
By the third week in May, leaf rust was severe in plots and light
in most fields in north central Oklahoma. In plots in north
central Oklahoma, 60% severities were reported on flag leaves of
susceptible cultivars such as Chisholm, Karl 92, and Jagger.
However, severities of less than 2% were observed on cultivars
like 2163 , Custer, and Tomahawk. Rust was severe in some fields
in central Oklahoma where wheat was planted early, which allowed
fall infection and overwintering of leaf rust.
During the last week in April, traces of leaf rust were found on
Triticum cylindrica (Aegilops cylindrica) plants growing along the
roadside in north central Texas. The pathotype (race) generally
identified from these collections normally does not infect the
commonly grown wheat cultivars. By the third week in May, leaf
rust severities ranging from 10 - 40% were observed on Triticum
cylindrica plants growing alongside the road in north central
Oklahoma.
Central Plains - In Kansas, the fall of 1998 was long and warm
with frequent rains which allowed for the buildup of leaf rust on
susceptible varieties. The winter was relatively mild but a cold
snap in late December killed many of the leaves. By early March,
overwintered leaf rust was found in northwestern and northeastern
Kansas, but overwintering was generally light and localized. Cool
weather in late April and early May slowed rust development. In
early May, traces of leaf rust were found on the flag leaves of
susceptible wheat cultivars in fields in the southern half of
Kansas. During the third week in May, in a south central Kansas
nursery plot, 40% leaf rust severities were reported on the flag
leaves of susceptible cultivars (e.g., TAM 107). Severities of
10% were found on flag-1 leaves in fields of the cultivar Jagger
in southeastern Kansas in mid-May. In some central Kansas fields,
the flag leaves were clean, but the flag-1 leaves had leaf rust
severities of trace to 5%. The northward development of leaf rust
was slow into the Great Plains states because of the cooler than
normal weather and moist conditions which kept the spores within
the crop canopy. However, with the advent of better weather
conditions for spore increase, during late May, trace to 80%
severities were reported in south central Kansas nurseries. In
fields in the same area, 20% severities were observed on flag
leaves of susceptible cultivars like Jagger, but on most of the
other cultivars severities were much lower. In north central
Kansas, 20% severities were observed on the lower leaves.
In early June, only traces of leaf rust were found in eastern
Colorado. The leaf rust is less than in prior years, partly
because less acreage of the common susceptible cultivar TAM 107 is
being grown. By mid-June in the central plains, 80% leaf rust
severities were common on susceptible cultivars such as TAM 107
from southeastern Colorado to north central Kansas. Leaf rust
developed late, but still managed to kill the flag leaves of
susceptible cultivars during the soft dough stage throughout much
of this area.
This year the overall estimated loss due to leaf rust in Kansas
was 3.4%, which is below the 10-year average of 5%, but above last
year¹s estimate of 2.5%. Yield losses were estimated from
fungicide plot data, cultivar surveys, cultivar disease ratings
and disease surveys. Several varieties such as Big Dawg, Custer,
Dominator, Heyne, and Jagger showed significant loss of resistance
compared to last year in most Kansas plots.
During the first week in June, traces of leaf rust were found in a
southeastern Nebraska winter wheat nursery. By mid-June, leaf
rust was light in many fields in southern Nebraska and severe in
some fields of susceptible cultivars where rust had been infected
early in the spring or where rust overwintered.
Northern Plains - In late May, traces of leaf rust were found in
winter wheat plots in Brookings, South Dakota. Growth stages
ranged from emergence of flag leaf to late boot. On May 27,
traces of leaf rust were observed on the lower leaves of the
winter wheat cultivar Norstar in a southeastern North Dakota plot.
On June 3, trace to 1% severities were found in a plot of the
winter wheat Roughrider in east central Minnesota. Traces of rust
were also observed on other winter wheat cultivars. The rust
development in the northern Great Plains states probably
originated from rust spores that were deposited with rain in mid-
May. This rust development was earlier than normal. During the
first week in June, 5-30% severities were reported in a winter
wheat nursery and traces in spring wheat fields in southeastern
South Dakota. By mid-June, 20% severities were observed on the
flag leaves of susceptible winter wheats and 30% on lower leaves
of susceptible spring wheats in east central South Dakota. Leaf
rust developed faster in this area than last year.
During the final week in June, leaf rust severities ranged from
trace to 60% on flag leaves of susceptible winter wheat cultivars
in central and eastern South Dakota plots and fields. Winter
wheat flag leaves dried up quickly because of heavy leaf rust
infection throughout South Dakota and southern Minnesota. The
rust infections in South Dakota and Minnesota probably originated
from inoculum sources in Oklahoma and northern Texas. During the
final week in June, leaf rust severities of 10% were reported on
the flag leaves and 60% severities on lower leaves of susceptible
spring wheat cultivars, e.g., 2375, in plots in southwestern and
west central Minnesota. In fields, severities ranged from trace
to 10% on the lower leaves of spring wheats in western Minnesota
and northeastern South Dakota. This year, leaf rust is more
severe and concentrated in the Upper Midwest than it has been in
the last 20 years. Abundant inoculum from the south has been
deposited with the frequent rains, and weather conditions favored
infection. The spring wheat cultivars currently grown are more
susceptible than those in previous years.
By mid-July, 40% severities were common on flag leaves of spring
wheat cultivars, e.g., Oxen, growing in plots in west central
Minnesota. In spring wheat fields, 20% severities at the early
berry stage were common throughout west central Minnesota and east
central South Dakota. By late July, 40% severities were reported
in spring wheat cultivars in a northeastern Montana nursery and
10% in spring wheat fields in north central North Dakota. This
year, yield losses to leaf rust are expected in both winter and
spring wheats in the Northern Plains.
Southeast - In February, heavy rainfall in Louisiana did not
allow the rust spores to move up the plants and therefore rust
development was limited. By mid-March, wheat leaf rust was
increasing in plots of southern soft red winter wheat cultivars in
southern Louisiana.
In much of the southeastern U.S., dry weather through March and
some of April was a limiting factor in rust development. In mid-
April, leaf rust was severe in plots of susceptible southern soft
red winter wheat cultivars within approximately 75 miles of the
Gulf Coast, and some cultivars that previously were resistant
showed significant rust development this year. During the last
week in April in the southeastern U.S., severities of 60% were
observed in plots of susceptible soft red winter cultivars, while
in fields, 1% severities were common on the flag leaves. The
drier and cooler than normal conditions during the last part of
April slowed the rust development. Due to the low relative
humidities during the last half of April, there was little dew
formation which is needed for rust infection to occur. Therefore,
the numbers of spores released as inoculum were lessened for areas
farther north. This year losses to leaf rust in the southeastern
soft red winter wheat area were less than normal.
During mid-April, traces of leaf rust were found in southern
Arkansas. By the third week in May, leaf rust was heavier than
normal in Arkansas. Wheat in the southern part of the state was
too mature for rust to cause much loss. In northern Arkansas
(north of I-40), losses occurred in fields that were later than
normal in maturity. This area provided a source of inoculum for
areas to the north. In some fields in this area, leaf rust
development was stopped by severe Septoria infection of leaves.
In mid-April, 40% severities of leaf rust were found on wheat in
east central South Carolina plots.
Midwest - By the first week in June, 20-30% leaf rust severities
were observed on susceptible wheat cultivars at the late milk
stage of development, in southwestern Indiana and western Kentucky
plots. Leaf rust severities of 40% were observed in wheat fields
at full berry stage in northeast Missouri on June 7 and severities
in plots in the area ranged from trace to 40%.
By the second week in June, 40% leaf rust severities were reported
in plots of susceptible wheat cultivars from northeastern Missouri
to northeastern Indiana. In fields of the susceptible cultivar
Clark in southern Illinois, 80% rust severities were common during
the second week in June. In plots and fields in places like east
central Indiana, 20% severities were noted on only 10% of the
wheat plants, because there was not enough dew or rainfall in late
May to allow the infection process to occur and, therefore, rust
did not spread from wheat plants infected earlier.
During the third week in May, traces of leaf rust were reported in
south central Michigan. Leaf rust (low to moderate incidences and
low severities) were found in southwest Michigan fields by June 8.
The infections were predominantly on the lower leaves.
East - During the last week in May, 80% leaf rust severities were
observed on susceptible winter wheat cultivars in eastern
Viriginia plots and traces of rust were found on wheat in west
central New York fields. This year leaf rust was not a problem in
the eastern U.S. because conditions were so dry rust infection
could not occur.
California - In early May, 20% leaf rust severities were reported
on wheat lines growing in a nursery in the northern Sacramento
Valley. By mid-May, late infections of wheat leaf rust occurred
throughout the Central Valley, but because the infections were so
late, losses were minimal. Disease levels were much lower this
year than in previous years because of the cool spring and a cold
spell in late December, which killed some of the early rust-
infected wheat.
Pacific Northwest - By the third week in May, leaf rust was just
starting to show in nurseries in western Oregon, but none was
found in commercial fields. In eastern Oregon, wheat leaf rust
was light because of the cool dry May.
During mid-April, leaf rust was light in wheat plots in the Skagit
valley of western Washington. Because of the cool dry May, leaf
rust increased at a slow rate in the state of Washington. By the
second week in June in western Washington plots, 50% severities
were reported on winter wheats and traces on the springs. In mid-
June, traces of leaf rust were found on spring wheats in eastern
Washington plots. By late June, wheat leaf rust was increasing on
spring wheats in the Mount Vernon area of western Washington. In
early July, traces of leaf rust were found in eastern Washington
and northern Idaho fields. In mid-July, leaf rust was increasing
on spring wheats in western Washington. Leaf rust was very light
east of the Cascades in Washington. The cool dry conditions in
early spring were not conducive for leaf rust to develop and
losses were light this year in the Pacific Northwest.
The wheat leaf rust races identified so far in the 1999 survey are
presented in Table 2. Most of the identified races were from
collections made in Texas in early spring, and again, as in
previous years, there is a large diversified population of races.
TABLE 2. Wheat leaf rust races identified through July 30, 1999
____________________________________________________________
Number of isolates by state
____________________________
Code Virulence formula AL CA FL GA KY LA MS SC TX
____________________________________________________________
CCRQ 3,3ka,11,30,10,18,26 2
FCGQ 2c,3,10,11,18,26 2
MBDL 1,3,10,17 2
MBGL 1,3,10,11 2 4 2
MBGQ 1,3,10,11,18 1
MBHL 1,3,10,11,18,30 2 2
MBRL 1,3,3ka,10,11,30 6 4 2 3 3
MBRQ 1,3,3ka,11,18,30 4 2 1 4
MCDL 1,3,10,17,26 16
MCRL 1,3,3ka,10,11,26,30 1
MCRQ 1,3,3ka,10,11,18,26,30 23 6 2 3
MCTL 1,3,3ka,10,11,17,26,30 2 2
MDBL 1,3,3ka,24 1
MDRL 1,3,3ka,10,11,24,30 2 2 11
MFBL 1,3,10,24,26 2 1
MJDL 1,3,10,16,17,24 1
MJTL 1,3,3ka,10,11,16,17,24,30 1
PCRQ 1,2c,3,3ka,10,11,18,26,30 1
TBBL 1,2a,2c,3,10 1
TBRL 1,2a,2c,3,3ka,11,3 3
TCRL 1,2a,2c,3,3ka,10,11,26,30 2 1
TCRQ 1,2a,2c,3,3ka,10,11,18,26,30 2
TFBL 1,2a,2c,3,10,24,26 2
TFBQ 1,2a,2c,3,10,18,24,26 4
TFRL 1,2a,2c,3,3ka,10,11,24,26,30 11
TLGG 1,2a,2c,3,9,11,18 2 4
____________________________________________________________
No. of isol. 39 2 13 6 4 21 13 4 55
No. of coll. 20 1 7 3 2 13 7 2 30
____________________________________________________________
1 Race code, see Phytopathology 79:525-529.
2 Single gene resistances evaluated:
Lr1,2a,2c,3,3ka,9,10,11,16,17, 18,24,26,30.
Wheat stripe rust
The first report of stripe rust this year in the central part of the
U.S. was in a south central Kansas nursery, during the last week
in May. Wheat stripe rust foci were found in some plots like 2137
and rust traces were scattered throughout the central and southern
parts of the state. Where this rust originated from is anybody¹s
guess, since this was the first report this year of stripe rust
being found in the central part of the U.S. Last year light
amounts of wheat stripe rust were scattered from the lower
Mississippi Valley north to east central Minnesota. In Kansas,
the cool spring weather allowed development of stripe rust, but
the hot temperatures of early June disrupted further development
and losses were negligible.
During the third week in June, traces of stripe rust were found in
east central Colorado fields. Normally, stripe rust is found at
higher elevations in Colorado, i.e, San Luis Valley (7,500 ft) or
front range of the Rockies (~5,000 ft).
In early June, light amounts of stripe rust were observed in wheat
plots in west central Indiana.
During mid-April, wheat stripe rust was severe in a field in the
Sacramento Valley of California. In other fields, in the same
area, severe rust was expressed in small foci. By the first week
in May, wheat stripe rust was increasing in the Sacramento Valley
in California, where temperatures remained relatively cool.
Disease foci readings ranged from 1 to 80% severities in fields of
the fall-sown hard red spring wheat cultivars Express and RSI 5,
the predominant cultivars grown in the Sacramento Valley. During
the third week in May, because of the cool weather, wheat stripe
rust was continuing to increase in fields in the Sacramento and
San Joaquin Valleys in California. Yield losses were low because
in most of the fields the rust was late in developing and the
wheat was grain filling when the infection began.
In mid-April, wheat stripe rust severities of 30% were reported on
susceptible winter wheat lines in the Skagit valley nursery in
western Washington. In late May in western Oregon nurseries,
wheat stripe rust was starting to show, but none was found in
commercial fields. During the last week in May, 80% wheat stripe
rust severities were reported on susceptible winter wheat lines in
northwestern Washington plots at the boot stage. In mid-June, on
spring wheats, 60% severities were observed in western Washington.
Wheat cultivars with adult-plant resistance continued to provide
durable resistance in farmers¹ fields. Stripe rust foci of 60%
severity were found in winter wheat plots in eastern Washington,
but the foci were few in number. The dry fall and cool dry May
led to the low rust severities, but the rains in mid-June improved
conditions for rust buildup.
By late June, wheat stripe rust was increasing on spring wheats in
the Pacific Northwest, but rust losses were minimal, since most of
the cultivars have high temperature, adult plant resistance.
During mid-July, 100% stripe rust severities were reported on
susceptible spring wheat cultivars in the Mount Vernon area of
western Washington. In mid-July, wheat stripe rust was increasing
in spring wheat fields in the Palouse region of Washington, but
the adult plant resistance of commercial cultivars minimized
losses.
In early July, significant amounts of wheat stripe rust were
reported in nurseries in the Bozeman area of Montana.
Oat stem rust
On March 15, twenty-percent oat stem rust severities were found on
volunteer plants growing around the edges of a non-cultivated
field in south Texas. Last year in the same field, the oat plants
were destroyed by stem rust. No other oat stem rust was found on
oat fields within the immediate area of these infections. By late
April, oat stem rust had killed some of the cultivars growing in
plots in a south Texas nursery. In mid-May, severe stem rust
severities were reported on some lines in central Texas.
In early April, oat stem rust was found in southern Louisiana
nurseries. By April 20 stem rust was severe in the Baton Rouge
plots and had killed 50% of the lines. This was the most oat stem
rust that had been observed in these plots in the last 10 years.
During the last week in April, oat stem rust severities ranged
from 1 to 20% in oat plots in central Louisiana and traces in
southern Alabama. In general, oat stem rust development was less
prevalent than last year throughout the southern U.S. Oat acreage
is minimal from Texas to southern South Dakota. In 1999, the next
report of oat stem rust was during late June, when traces of rust
were found in a commercial field in central Nebraska.
By mid-July, trace to 20% severities of oat stem rust were reported
in plots and fields from south central Minnesota to central North
Dakota. The 20% severities represented foci of oat stem rust in
plots throughout the Northern Plains. In mid-July, traces of oat
stem rust were reported in northeastern Montana plots and 60%
severities in east central North Dakota plots. The widespread
distribution of oat stem rust in the Northern Plains this year was
unexpected, because stem rust was less prevalent than normal on
oats in the southern U.S., which is the source of inoculum for
northern states. In 1999, light losses to oat stem rust will
occur in some fields in the Northern Great Plains.
From oat stem rust collections made in Texas, Alabama and Louisiana,
the common pathotype NA-27 was identified.
Oat crown rust
During mid-March, crown rust was severe in southern Texas plots and
fields. Foci of sixty-percent severity were common on the most
susceptible cultivars in nursery plots. In southern Texas oat
fields, rust severities ranged from 1 to 20%; on average, rust
development was equal to last year.
In mid-April, crown rust was severe from central Texas through
southern Louisiana to the panhandle of Florida. During mid-April,
30-50% crown rust severities were observed on susceptible oat
plots in Baton Rouge, Louisiana and Fairhope, Alabama. By late
April, crown rust was severe in plots of susceptible cultivars and
light in commercial fields in the southern U.S. These southern
areas provided some inoculum for areas farther north.
In mid-May, 70-80% severities were observed on susceptible oat
cultivars like Simpson growing in the Blackville, South Carolina
area (southwest SC). However, at Florence (east central) and
Clemson (northwest) South Carolina, no crown rust was found.
In mid-June, traces of oat crown rust were found in fields and plots
in northern Kansas and northeastern Indiana at the full berry
stage.
By late April, pycnial infection was noted on buckthorn bushes in
southeastern Minnesota and in the St. Paul buckthorn nursery. At
St. Paul, most of the pycnia were found along the edge of the
nursery, rather than where the oat telial straw was located.
Therefore, the first pycnia observed may have been forms that
infect grasses rather than oat. The pycnia development was later
than normal this year in the St. Paul nursery. This suggests that
the release of basidiospores peaked later this year, relative to
the development of the buckthorn leaves which were 7-10 days
behind last year.
By the fourth week of May, there was abundant crown rust infection
on buckthorn at St. Paul, but no uredinia were found on oats in
the buckthorn nursery. The first pycnia appeared on the buckthorn
in mid- to late April, but the main flush of new pycnia did not
appear in the buckthorn nursery at St. Paul until the second week
of May. Most of the new infections had few aeciospores. Cool
weather delayed development of aecia. Scattered pustules of crown
rust were found on oats in the buckthorn nursery at St. Paul on
June 4. This was four weeks later than last year, but close to
normal for most years. By mid-June, oats in the buckthorn nursery
in St. Paul, Minnesota, had moderate crown rust infection on lower
leaves, but little or no rust had appeared on the upper leaves.
In late June, 60% severities were observed in oat plots in south
central Minnesota, while in fields 1-5% severities were found on
the lower leaves. During mid-July, crown rust severities ranged
from 0 to 20% in oat fields and trace to 60% on flag leaves in
plots in west central Minnesota.
In early May, heavy infections of pycnia and some early stages of
aecia were observed on buckthorns at Brookings, South Dakota. By
the fourth week in May, buckthorns in east central South Dakota
were severely infected with crown rust. In late May, aeciospores
were released from crown rust-infected buckthorn bushes growing in
Fargo, North Dakota. The infections were moderate and most likely
from other grasses as there are no oats in the area. By late
June, crown rust had developed very slowly at the Brookings, South
Dakota nursery and trace to 20% severities were observed on lower
leaves of susceptible cultivars at the early milk growth stage.
During mid-July, crown rust severities ranged from 0 to 20% in oat
fields and trace to 60% on flag leaves in plots in northeastern
South Dakota. On wild oat (Avena fatua), rust severities ranged
from trace to 20% severity throughout eastern South Dakota.
In mid-July, traces of crown rust were seen in the nursery at Fargo,
North Dakota. By late July, 40% severities were observed in plots
and 5% in fields in northern North Dakota.
This year, throughout the upper Midwest, crown rust was lighter than
normal and covered a smaller area because of the cooler than
normal weather this spring, which decreased the amount of
infections from buckthorn, the alternate host of oat crown rust.
This year, losses to crown rust in northern oat-growing areas were
light.
Barley stem rust
The first report of barley stem rust in 1999 was in early July in
west central Minnesota where traces of stem rust were found on
the 2-row barley Hypana. Limited amounts of barley are grown
commercially in the southern states and stem rust on barley rarely
occurs in this area.
In early July, trace to 50% severities were reported on 6-rowed
barley in a north central South Dakota field. By mid-July, traces
of stem rust were common on both 2 and 6-rowed barleys growing in
plots and in fields in the southern part of the Red Valley of the
North. In late July, 40% severities were observed in plots in
northeastern North Dakota and traces in plots in northeastern
Montana. Most of these barley rust infections are probably due to
the increase in the QCCJ stem rust race which has been identified
in Texas and Louisiana as described in the wheat stem rust
section. The stem rust development in barley was more significant
than in the recent years but still losses will be minimal.
In mid-July, trace to 10% stem rust severities were reported on wild
barley (Hordeum jubatum) plants growing alongside the roadway in
eastern South Dakota. This was the most extensive stem rust
observed on wild barley in this area in the last 5 years.
Barley leaf rust
In mid-March, traces of leaf rust were observed on lower leaves in a
few barley plots in southern Texas. In late April, traces of
barley leaf rust were found on cultivars growing in nurseries in
central Texas.
In early May, traces of barley leaf rust were found in the Skagit
Valley of western Washington. During late May, barley leaf rust
was increasing on the winter barleys and traces were found on the
spring barleys in northwestern Washington. During the third week
in June, barley leaf rust severities of 50% were reported on
susceptible winter barleys in western Washington. Rust was just
starting to increase on spring barleys. No barley leaf rust was
reported in eastern Washington.
In late June, severities of 20% were reported on the lower leaves in
spring barley plots in east central Nebraska and traces in plots
in west central Minnesota. In mid-July, trace to 10% leaf rust
severities were observed in barley plots in south central
Minnesota, east central South Dakota and southeastern North
Dakota.
Losses to barley leaf rust were light in the U.S. this year.
Stripe rust on barley
In mid-April, barley stripe rust severities of 80-100% were reported
in susceptible plots on the University of California-Davis
agronomy farm. By early May, barley stripe rust was observed in
nurseries in the Sacramento and San Joaquin Valleys of California
at severities of 80-100%. Barley stripe rust development was much
less than last year in California.
In mid-April, severities of less than 1% were noted on barley lines
in the Skagit Valley nursery of western Washington. Crop maturity
was delayed, but the cooler than normal conditions also delayed
rust development. By the third week in May, foci of stripe rust
were found in barley plots at Corvallis, Oregon. By mid-June, in
the Pacific Northwest, stripe rust on barley was much less than
last year. In western Washington, 30% severities were observed on
susceptible barley cultivars, while in eastern Washington no
stripe rust on barley was found. The dry fall and cool dry May,
which is the critical month for rust development, were not
conducive for the disease.
In late June, barley stripe rust was increasing on susceptible
cultivars in western Washington, while only traces were found in
plots in eastern Washington. There is much less stripe rust than
last year throughout the Pacific Northwest. In mid-July, stripe
rust on barley was increasing in the Pacific Northwest, but there
was much less rust than last year. Losses to stripe rust on
barley will be significantly less than last year in the Pacific
Northwest.
Barley stripe rust was virtually non-existent in Idaho this
year,with the exception of a severely diseased field of spring
barley in eastern Idaho.
In early July, trace amounts of stripe rust were reported in the
Bozeman area of Montana.
Barley crown rust. Moderate levels of aecial infection were
observed on buckthorn in the barley crown rust nursery in Fargo,
North Dakota, the week of May 24. In mid-June, infection on
barley was light. By late July, crown rust was severe on barley
in plots at Fargo.
In mid-June, a few pustules of barley crown rust were seen on winter
rye in southeastern South Dakota plots.
Rye leaf rust
During mid-March, rye leaf rust foci with 10% severities were found
on leaves of winter rye in southern Texas. In late April, 10%
severities were observed on flag leaves in rye fields in southern
Alabama and central Texas. Rye leaf rust had developed late in
plots in southern Georgia and caused minimal losses.
During the third week in May, 20% leaf rust severities were observed
in rye fields in north central Oklahoma.
By the last week in May, traces of rye leaf rust were found in a
field in south central Wisconsin. In early June, 10% severities
were observed on the lower leaves of winter rye in southeastern
South Dakota plots.
In mid-June, 10% leaf rust severities were reported in rye fields
in northeastern Indiana.
By the fourth week in June, 20% severities of leaf rust were found
on lower leaves of spring rye in plots in southern and west
central Minnesota. By mid-July, 60% severities were observed on
the flag leaves of spring rye in west central Minnesota plots.
In 1999, rye leaf rust was scattered throughout the U.S. but only
caused light losses.
Rye stem rust
During late April, traces of rye stem rust were found in a field in
central Texas. This was the only report of rye stem rust in the
U.S. in 1999.
Stem rust on barberry
In late April, the pycnia stage of wheat stem rust was found on
barberry leaves in southeastern Minnesota and the aecia stage was
found at two locations in south central Wisconsin on the common
susceptible barberry (Berberis vulgaris).
In mid-June, a few aecial infections were observed on common
barberry bushes in south central Wisconsin.
Other grasses
In mid-July, 10% crown rust severities were common on Elytrigia
(Agropyron) repens (quackgrass) in eastern and central North
Dakota.
This is the last issue of the Cereal Rust Bulletins for the 1998-99
growing season. I would like to thank all of those who helped
with the bulletin this year, especially Mark Hughes
(markh@puccini.crl.umn.edu) who coordinates its distribution
through the CDL web page (http://www.cdl.umn.edu), email and the
post. Any reports of rust that you find in your area will be
appreciated and this information may be added on our web page. -
David Long (davidl@puccini.crl.umn.edu)