May 19,1923 
Life History of Stripe Rust 
619 
SUMMARY 
(1) Observations show that stripe rust, caused by Puccinia glumarum 
(Schm.) Erikss. and Henn., may overwinter on the Pacific coast, both as 
mycelium and as urediniospores, on wheat and wild grasses. It was 
possible to collect viable urediniospores during every month from Sep¬ 
tember, 1917, to July, 1918, at Corvallis, Oreg. 
(2) Although the experiments which have been carried on are not 
absolutely conclusive, there is good evidence that the mycelium of stripe 
rust may overwinter at Moscow, Idaho, on Hordetim jubatum and Bromus 
marginatus. 
(3) It has been found that the mycelium of stripe rust passes the dry 
summer months on the Pacific coast as dormant mycelium in the leaves 
of wild grasses. It is suggested that the climatic conditions which may 
prevail during the summer and fall of a given year determine whether or 
not an epidemic of stripe rust may develop upon winter wheat. The 
quantity of oversummering uredinia would be an important consideration 
in producing an epidemic on fall-sown wheat. 
(4) Germination tests with urediniospores of stripe rust show that when 
the leaves of the infected host are kept in herbarium packets at ordinary 
room temperature the spores may remain viable at least 58 days. Ure¬ 
diniospores on leaves of wheat kept in open vials in a desiccator gave a 
slight percentage of germination at the end of 63 days. Urediniospores 
taken from wheat leaves, placed on glass slides and kept in a protected 
place in the laboratory, gave a trace of germination in 23 days. 
(5) Urediniospores of P. glumarum tritici did not prove to be so resistant 
to desiccation as urediniospores of P. graminis avenae, P. triticinay or 
P. holcini, 
(6) It has been shown that infection by urediniospores of stripe rust 
can not take place before the primary leaf of the wheat seedling has 
begun to expand. 
(7) The period of incubation for the uredinial stage of stripe rust has 
been found to be 12 to 13 days under conditions favorable for infection. 
Low temperature and lack of sunlight may materially lengthen this period. 
(8) The uredinia and telia of stripe rust occur commonly upon kernels 
of certain varieties of wheat. As high as 60 per cent of the kernels of 
certain varieties grown in a rust nursery were infected. Over 35 per 
cent of infected kernels have been found in wheat grown under ordinary 
field conditions. 
(9) The germination of seed infected with stripe rust was only 50 per 
cent of that of the uninfected seed from the same seed lots. 
(10) Forty rows, each i rod long, of rust-infected seed of several varie¬ 
ties of wheat were sown on October 10, 1917. No stripe rust developed 
on the plants from this seed before the next spring. Plants from clean 
seed sown at the same time became infected the next spring at about the 
same date as the plants from the infected seed. 
(i i) More than 4,700 plants were grown from rust-infected wheat seed 
in a specially constructed room in the pathological greenhouse at the 
Oregon Agricultural College, and no rust appeared upon any of them at 
any time. 
(12) No infection appeared upon plants grown from wheat seed which 
had been covered with viable urediniospores of stripe rust before sowing. 
(13) The results of the experiments here reported indicated that stripe 
rust can easily overwinter in the uredinial stage on the Pacific coast and 
