4 BULLETIN 1239, U. S. DEPARTMENT OF AGRICULTURE. 
Table 1. — Results of seeding wheat at successive dates, in duplicate plats, to deter- 
mine soil infestation by bunt, at Pullman, Wash., in 1915. 
Date sown, 1915. 
Infected plants (per cent). Infected plants (per cent). 
Date sown, 1915. 
Plat 1. Plat 2. Average. 
Aug.21 J 
Aug.26 
Aug. 31 
Sept. 2 
Sept. 4 20.0 
Sept. 14 21.3 
Sept. 17 i 40.5 
Sept. 19 58.1 
Sept. 21 
Sept. 23 
Sept. 28 
< Oct. 3 
25.9 Oct. 8 
_..7 0:t.ll... 
40.9 O.t.18 
59.1 Oct. 25 
Plat 1. 
Plat 2. 
Average. 
37.7 
36.4 
24.0 
35. 
5.9 
12.9 
6.3 

37.7 
37.3 
30.7 
35 
5.9 
14.1 
7.6 
.9 
13.5 
7.0 
.5 
In the earlier sowings it was necessary to irrigate in the row to 
obtain immediate growth. Fall rains began on September 7 and 
the soil was thoroughly wet by September 15 to 17. Contemporane- 
ous sowings were made from the same seed lot in plats that had been 
hand inoculated with bunt at different times in order to determine 
the duration of infection conditions resulting from spores in the soil. 
It so happened that these plats were in an open, comparatively 
level spot where the wind was uninterrupted. Sowings in these 
Elats on dates corresponding to those in Table 1 produced much less 
unt, notwithstanding the fact that they had at some time been 
dressed with bunt, either in heads or pulverized. After the 1915 
harvest was partly completed, Heald and George (12) 7 installed 
spore traps and demonstrated the fall of spores. They continued 
the work in 1916 (August 15). During that year the spore fall 
from August 15 to October 31 at the experiment plats aggregated 
more than 43,000 spores per square inch. 
Table 2. 
(The aggres 
— Relation of the date of seeding to the percentage of bunt in wheat sown 
at intervals between August 11 and October 30, 1916. 
ate precipitations o f bunt spores per square inch, as given, are these shown by spore-trap 
collections on approximately the same dates.] 
Aug. 11. 
Aug. 24. 
Sept. 4.. 
Sept. 8. 
Sept. 11. 
Sept. 11. 
Sept. 21. 
Sept. 25. 
Oct. 2.. 
Oct. 10. 
Oct. Is. 
Oct. '50. 
Date so^n. 
Bunt- 
frcc 
"heat 
heads. 
(a) 
1,712 
1,352 
1.17:; 
1.205 
Bunted heads. 
Xumber. Percent 
1,338 
1,517 
836 
7.")') 
1 •_'•_• 
51.-. 
C.s7 
131 
(6) 
31 
119 
17t 
280 
223 
177 
514 
339 
295 
111 
]■>•> 
17 
1.7n 
• 
12.92 
18.86 
14. 29 
Hi. 27 
38. 07 
30. 9!) 
11.14 
16.92 
15.08 
11. 19 
Spore-trap collec- 
tions. 
Date. 
Arg. 22 
Aug. 29 
Sept. 5 
Sept. 12 
Sept 19 
Sept, 26 
Oct. 3 
Oct. 10 
Oft. 17 
Oct. 34 
Agere- 
gate 
number 
of spores. 
1,121 
14.44'J 
27,445 
H,050 
12.000 
43.022 
a Not counted. b N ' plants. 
*The serial numbers (italic) in parentheses refer to "Literature cited," at the end of this bulletin. 
