CEREAL RUST BULLETIN       
 Report No. 9
 July 22, 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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 ________________________________________________________________
 
 €Stem rust has shown up unexpectedly in plots of wheat, oat and
 barley in the northern plains.
 
 €Wheat leaf rust in the northern plains is more severe than in
 recent years.
 ________________________________________________________________
 
 
 The winter wheat harvest has begun from southwestern New York to
 northeastern South Dakota.  In the northern Great Plains,
 persistent wet weather has reduced the potential yield of small
 grains in some locations, but more than half of the spring-sown
 grains are still rated in good to excellent condition.  In spite
 of recent wet weather, spring-sown crops remain a few days behind
 normal crop development due to unusually cool weather earlier in
 the summer.
 
 
 
 Wheat stem rust
 In mid-July, traces of wheat stem rust were found in 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 east central South Dakota plots. 
 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 ago.  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 are known to
 have existed at the time those infections occurred.  This year
 there have been few reports of stem rust in fields and nurseries
 and numbers of rusted collections received at the Cereal Rust Lab
 are 1/3 of normal. 
 
 In early July, stem rust was found in a nursery in south central
 Virginia.  This is the first report of stem rust this year in the
 eastern soft red winter wheat area.  
 
 In mid-July, small foci of stem rust were found on winter wheat
 cultivars in the Palouse region of the Pacific Northwest.  In late
 maturing cultivars like Eltan, stem rust may cause some yield
 losses.  Stem rust infection was light on a few of the spring
 wheat cultivars in the Pacific Northwest.
 
 
 Wheat leaf rust
 As indicated in the previous Cereal Rust Bulletin, leaf rust was
 unusually severe on winter wheat in the northern Great Plains this
 year.  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.  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.  During
 the second week in July, 60% severities were observed in fields of
 winter wheat at the mid-dough stage in southeastern North Dakota. 
 As in South Dakota, some yield losses from leaf rust are expected
 in winter wheat in North Dakota.
 
 In mid-July, wheat leaf rust was increasing in the Palouse region of
 Washington in fields and nurseries, but it is too late for any
 yield loss in winter wheats.
 
 
 Wheat stripe rust
 During mid-July, wheat stripe rust was increasing in fields in the
 Palouse region of Washington, but the adult plant resistance of
 commercial cultivars should keep losses to a minimum.
 
 
 Oat stem rust
 In mid-July, traces of oat stem rust were found in plots in east
 central South Dakota and west central Minnesota.  These are the
 first reports of oat stem in the U.S. since late April, when oat
 stem rust was found in fields and plots in Louisiana and Alabama.
 
 
 Oat crown rust
 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, east central North Dakota, west central Minnesota
 and southern Wisconsin.  In east central Minnesota plots, 80%
 severities were observed on flag leaves of the most susceptible
 cultivars.  No crown rust was found in oat plots in central South
 Dakota.  In clumps of wild oats growing in small grain fields in
 east central North Dakota, crown rust severities ranged from 0 to
 20% on individual plants. The cooler than normal weather in early
 June delayed rust development but warmer than normal temperatures
 the past two weeks favored crown rust increase.  Rainy weather,
 however, has washed much of the inoculum off infected plants
 before spores could spread.
 
 
 Barley stem rust
 In mid-July, traces of barley stem rust were found on spring barleys
 in east central South Dakota plots.  The last time barley stem
 rust was reported in the U.S., was May 19 in south Texas.
 
 
 Barley leaf rust
 In mid-July, trace - 40% barley leaf rust severities were observed
 in barley plots and none in fields in west central Minnesota and
 northeastern South Dakota.
 
 
 Stripe rust on barley
 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.  In mid-July,
 70% severities were observed in spring barley test plots in west
 central Idaho and traces in the northern tip of Idaho and since
 the plants were in an advanced plant growth stage the rust should
 not significantly affect the yield.
 
 
 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.  In mid-July, 20% crown rust severities were
 observed on flag leaves of susceptible lines in an east central
 South Dakota barley nursery.  
 
 
 Rye rusts
 In late June, 20% rye leaf rust severities were reported in a winter
 wheat nursery and field in east central North 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.