224 
Journal of Agricultural Research y 0 i. xxix, No. 5 
Table II .—Meteorologic data for the period January to December, 1914, 1915 r 
and 1916, inclusive, recorded at the Sherman County Branch Station, Moro, Oreg . 
Month 
Air temperatures (°F.) 
Precipitation 
(inches) 
Evaporation 
(inches) 
M aximum 
Minimum 
Mean 
1914 
1915 
1916 
1914 
191511916 
1914 
1915 
1916 
1914 
1915 
1916 
1914 1915 
1916 
January 
43 
41 
20 
30 
10 
10 
36 
26.0 
15.0 
2.20 
1.75 
1.10 
February - _ 
39 
52 
35 
27 
23 
26 
33 
36.0 
30. 5 
1.16 
2.31 
2. 43 
March . _ 
54 
70 
50 
34 
30 
35 
44 
45.0 
42. 5 
. 11 
1.27 
2. 05 
April_ 
59 
75 
59 
39 
32 
37 
49 
50.8 
48.0 
2.06 
.65 
.75 
4.01 j 5.23 
4.80 
May._ 
70 
78 
61 
42 
34 
39 
56 
53.0 
50.0 
.76 
2.06 
1.37 
7.43 | 5. 73 
5.68- 
June__ 
72 
93 
72 
47 
40 
47 
59 
60.0 
59.5 
.66 
.36 
1.98 
8. 29 ! 8. 24 
6.80 
July_ 
85 
96 
74 
56 
40 
51 
70 
64.8 
62.5 
.08 
.57 
.92 
11.43 ! 8.95 
7.88- 
August_ 
85 
100 
82 
54 
46 
54 
69 
71.3 
68.0 
Trace 
.05 
.15 
9.64 | 9.61 
7.50 
September...._ 
67 
86 
72 
44 
36 
45 
55 
57.3 
58.5 
1.05 
1.14 
.33 
4.40 [ 5.23 
4.68. 
October_ 
59 
73 
62 
40 
33 
34 
49 
50.6 
48.0 
1.48 
.23 
.39 
2.19 j 2. 93 
2. 81 
November.. 
47 
54 
41 
30 
25 
26 
38 
38.2 
33.5 
.88 
2.89 
1.69 
_1 .45 
_ 
December 
28 
53 
35 
17 
11 
23 
23 
32. 8 
29.0 
.88 
1.61 
1.32 
! ; 
According to Lang (15), who has 
made a careful investigation of climatic 
factors in relation to the occurrence of 
stripe rust in Europe, the following 
comprise the conditions typical of a 
severe epidemic: An abundance of hi¬ 
bernating mycelium, followed by the 
development of uredinia in late March 
or early April. This first crop of 
urediniospores, favored by congenial 
conditions for germination and incu¬ 
bation, will give rise to a second, and 
from the second a third crop of spores. 
Thus, by early May, assuming condi¬ 
tions to be ideal, a severe and general 
epidemic will have developed. Spring 
wheat sown in April will become in¬ 
fected by the middle of May, and by 
the end of the month the second prin¬ 
cipal outbreak of the rust will have 
occurred. 
Litvinov (17), commenting on the 
probable causes which contributed to 
the severe epidemic of stripe rust in 
central Russia in the summer of 1914, 
attributes the attack to favorable cli¬ 
matic factors. The spring of 1914 was 
relatively cool, but free from recurrent 
thaws. The general coolness of the 
spring contributed to the early develop¬ 
ment of urediniospores as contrasted 
with Puccinia triticina. His observa¬ 
tions were confined to experiments with 
varieties of spring wheat, in which he 
noted that susceptible early varieties 
were much more subject to damaging 
infection than were late-sown varieties 
of approximately equal susceptibility. 
Jenkin and Sampson (18) in Wales like¬ 
wise noted a correlation between date 
of seeding and severity of infection, but 
their results indicate that the severest 
infection develops on the latest-sown 
rather than on the earliest-sown plats. 
It is possible that this difference in cor¬ 
relation may be traced to differences in 
contingent climatic conditions which 
characterized the spring of 1914 at 
Voronezh and that of 1920 at Abery¬ 
stwyth. 
Although the foregoing instances of 
severe, even damaging, infection in 
spring wheat would seem to controvert 
the evidence adduced by the majority 
of the students of stripe rust to the 
effect that serious infection seldom 
develops in spring wheats, it should be 
pointed out that even such instances 
may be concerned with epidemics 
originating from mycelium which may 
have hibernated in some near-by grass 
host or in volunteer wheat plants. 
Thus it is conceivable that climatic 
conditions which favor a general seed¬ 
ling infection during the autumn 
months may contribute to the develop¬ 
ment of a high potential for a subse¬ 
quent and destructive epidemic during 
the spring and summer. But it is 
apparent that unless the fungus is 
favored by optimum spring conditions 
it will not develop to economic propor¬ 
tions. 
It is obvious from the foregoing that 
until a more extended and critical study 
has been made of all possible factors 
influencing infection by, and subse¬ 
quent development of, the stripe-rust 
fungus, it will not be possible to answer 
the many perplexing questions that 
must arise in the mind of the investi¬ 
gator. 
CONTROL OF STRIPE RUST 
The adoption of varieties of wheat 
resistant to stripe rust is the most 
practical means of control. Jenkin and 
Sampson (18) found that of the more 
than 90 varieties and strains of wheat 
