24 
THE WHITE-FUNGUS DISEASE IN KANSAS. 
of spores was thereby dislodged, which so filled the bottle that every 
chinch bug must have come into contact with them. 
On May 22 the results were as follows: 
Bottle No 
1 
2 
3 
4 
5 
6 
7 
8 
9 
10 
11 
12 
13 
Number of diseased bugs. 
Inoculated 
4 

8 

10 
1 
12 

12 
1 
11 

12 

10 

11 
1 
11 

8 
2 
9 
1 
1?, 
1 
Bottle No 
14 
15 
16 
17 
18 
19 
20 
21 
22 
23 
24 
Total. 
Number of diseased bugs. 
Inoculated 
Checks 
7 

12 10 
1 
6 

5 

9 

8 10 
1 
11 
2 
10 
1 
9 

227 
12 
Experiment 5. — The last of the series on virulence was begun on 
July 14, this late date being selected for the reason that the cultures 
then in the laboratory had been running saprophytically since the 
original isolation of the fungus in January, 1910, and there was a 
question whether such prolonged cultivation on artificial media had 
had the effect of lowering the virulence and hence weakening the 
power of the fungus in attacking chinch bugs. 
As the latter part of July was the time in which the field experi- 
ments were terminated, it was pertinent to know whether the fungus 
used in field inoculation during June and July had retained the 
parasitic nature evidenced by the earlier experiments of this series 
on virulence. Experiment 5 was arranged to compare inoculations 
with artificially grown fungus with natural infection. Natural infec- 
tion was presupposed, since there was no field found where Sporo- 
trichum did not exist naturally to some, even though to small, extent. 
The method of procedure differed but slightly from that in experi- 
ment 4. Forty screw-capped bottles were partially filled with 100 
grams each of moistened and thoroughly mixed earth. They were 
then sterilized with 15 pounds pressure in an autoclave. Ten adult 
chinch bugs were placed in each bottle. Twenty bottles were infected 
by the camel's-hair brush method described in experiment 4. The 
other 20 were checks. 
The bottles were watched, and it was soon noticed that Sporo- 
trichum was appearing among the treated bugs at a much faster rate 
than among the untreated. The disease in the checks was undoubt- 
edly introduced with the bugs and was present on them when they 
were collected from the field. But the same amount of natural 
fungus approximately would be present in the bugs in the inoculated 
bottles, so that final results would be but little affected. 
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