Friesia X, 4-5

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resemble the measurements deseribed for S. avenae f. sp . tritioea,
found by JOHNSON (1947) to attack barley lea ves.
On barley seed the occurrence of S. nodorum has been reported
by MACHACEK (1945) and NOBLE & RICHARDSON (1968) . At The Danish
State Seed Testing Station pycnidia of S. nodorum were found in
several seed lots in the years 1969-72 (JØRGENSEN 1973, pers. comm.) .
This pap er deals with the widespread occurrence of Septoria nodo­
rum and its sexual stage L eptosphaeria nodorum on barley in Den­
mark, and the physiologic sp ecialization of the pathogen on ba rley
and wheat .
As t his apparently is the first time Septoria nodorum ha s been
found associated with its sexual stage on barley, the name Lepto­
sphaeria nodorum will be used in the following.
OC CURRENCE OF L E P T O S P H A E R I A NODORUM
ON BARLEY IN DENMARK
During the growing-seasons 1970-71 disease symptoms, apparently
new t o Denmark, were frequently observed on barley leaves. The
symptoms were always associated with L eptosphaeria nodorum. In
1972-73 the pathogen was isolated from the folIowing localities in
Zealand and Jutland: Skalstrup, Snoldelev, Gadstrup, Ramsømagle,
Allerslev (all in Zealand) , Jelling, Hornborg, Tvingstrup, Horsens,
Langå and Randers (Jutland). At all of these localities the disease
symptoms were widely occurring. The most serious attacks were
found at Hornborg and Langå where 30-40 % of the barley plants
were infected with a considerable loss of active leaf tissue as a conse­
quence.
SYMPTOMS ON BARLEY
The first disease symptoms appear in Mayas brown or greyish
spots on the leaf lamina and leaf sheaths or at the junction between
the lamina and sheath. Later in the season lesions appear as 1-2 cm
long, oval or lens-shaped, redbrown spots often continuing in chloro­
tic tissue along the leafribs (Fig. 1) . More irregular or triangular
formed lesions typically develop at the junction between the leaf
lamina and sheath thereby affecting the entire leaf (Fig. 2) . Infected