6 BULLETIN 1239, U. S. DEPARTMENT OF AGRICULTURE. 
showed but 0.8 per cent of the plants affected with bunt. In the 
check plat 17.24 per cent of the plants were entirely smutted and 
7.47 per cent partially so, 24.71 per cent of the plants thus snowing 
infection. 
The prevalence of bunt in the Pacific Northwest is dependent on 
the summer-fallow system of farming and on the dry summers. 
Almost invariably the seed bed is prepared before the threshing 
begins. In most years rains are infrequent or entirely lacking from 
July 15 to early or middle September. During this period the spores 
settle on the dry surface and remain intact until the rains begin; 
then the spores begin to germinate and usually the farmer begins 
seeding soon after the first good rain. By this time the seed bed is 
thoroughly infested with the bunt organism at its optimum virulence. 
Concerning the duration of infective power of the spores, it can be 
said that it is dependent on a combination of temperature and mois- 
ture conditions and probably also on the bacterial and fungous flora 
of the soil. An examination of Table 1 shows that in 1915 their 
infective power was practically lost by October 25, or within five or 
six weeks after the soil became moist. 
DURATION OF VIABILITY OF BUNT SPORES IN THE SOIL. 
In order to determine just how long the bunt organism may retain 
its infective capacit}- when dispersed in the soil, crushed bunt balls 
were worked into the seed bed on March 5, 1915. The soil was in 
good tilth and sufficiently moist to favor germination and infection. 
Seed of the Early Wilbur variety was treated two hours in a 1 to 240 
solution of formaldehyde and sown on successive dates over a period 
of two months, during which time the conditions for infection were 
nearlv ideal. The dates of seeding and the results are presented in 
Table 4. 
On April 4 crushed bunt balls were worked into the soil, and 1-rod 
rows of Early Wilbur wheat were sown on successive dates during 
the period from April 4 to June 3, inclusive. The months of April 
and May were characterized by soil temperature and moisture condi- 
tions highly favorable to germination and infection. The seed was 
treated two hours in a 1 to 240 solution of formaldehyde and sown 
promptly after treatment. The data obtained are shown in Table 4. 
It is fairly certain that under the most favorable conditions the 
infective power of the bunt organism is lost within 30 days, provided 
there are no unbroken bunt balls. As to the overwintering of free 
spores in the soil the results at Pullman are in agreement with those 
of Tubeuf (22, 23), Appel and Riehm (4), and Steglich (21), that it 
does not occur. However, there may be exceptions. For example, 
if the spores were applied to a dry soil late in the fall, followed by 
freezing weather before precipitation, and should lie in this dry seed 
bed until spring, it is not only possible but probable that the spores 
would remain intact until spring. The spores of unbroken bunt 
balls and uninjured bunt heads lying on the surface of the soil 
suffer but little loss of viability in the course of a year. The length 
of time that the ball remains intact depends on soil and weather 
conditions. The final destruction of the testa of the bunt ball, like 
other vegetable matter, is greatly promoted by saprophytic fungi, 
two of which are especially active in the disintegration of bunt balls. 
One of these is a Cladosporium (perfect stage not determined), the 
