EFFECT OF STORAGE, HEAT, AND MOISTURE ON PYRETHRUM 
No. 5. Whole flower heads were kept in a tightly sealed fruit jar 
in the laboratory. 
No. 6. Powdered flower heads (80 mesh) were kept as in lot No. 5. 
At the times indicated in the table portions of these six lots were 
ground, sifted to 80 mesh, and tested against roaches by dipping 
the insects as described on page 1 . 
This table shows that an exposure to the weather for 12 weeks 
does not noticeably injure ground or whole flower heads, but that 
an exposure of 21 weeks materially reduces the efficiency of both, 
since at the end of this time they killed, in 120 hours, only 60 and 
70 per cent, respectively. 
When whole flower heads were exposed in an open dish in the 
laboratory for 150 weeks, they retained their full efficiency. Under 
the same conditions the powdered flower heads showed some de- 
terioration in 136 weeks, and were of almost no value at the end of 
150 weeks. Both flower heads and powder showed no loss of effi- 
ciency when kept in tightly closed jars for 150 weeks. 
EFFECT OF STORAGE IN SEALED GLASS CONTAINERS 
Tables II and III give a comparison of the effectiveness against 
aphids and roaches of whole and ground pyrethrum flower heads 
stored in glass containers for 5^ years. 
The materials considered in these tables were received as whole 
flower heads in 1911. A portion of each sample was ground early 
in 1912 and stored in a tightly stoppered bottle. The remaining 
flower heads were stored in sealed fruit jars under the same condi- 
tions until March, 1918, when a portion of each lot was ground and 
tested in comparison with the powders prepared in 1912. 
Table II. — A comparison of the effectiveness against aphids of whole and ground pyr- 
ethrum flower heads stored in glass containers for 5\ years. One nasturtium plant, 
grossly infested with aphids, dusted in each test 
No. 
Material. 
Num- 
ber of 
tests. 
Ground in spring 
of 1912; tested 
March, 1918. 
Num- 
ber of 
tests. 
Ground and tested, March, 1918. 
1 
2 
California flowers 
Montenegrin flowers 
Dalmatian flowers 
4 
4 
4 
Ineffective 
do 
4 
4 
2 
80-90 per cent killed or repelled. 
80-95 per cent killed or repelled. 
3 
do 
90 per cent killed or repelled. 
Table III. — A comparison of the effectiveness against roaches of ground and whole 
pyrethrum flower heads stored in glass containers for 5\ years. Ten roaches dipped for 
each test 
No. 
Material. 
Ground in spring of 1912, tested March, 
1918— Hours required to kill roaches. 
Ground and tested in March 
1918 — Hours required to 
kill- 
First 
roach. 
Last 
roach. 
Average. 
1 ! California, flowers 
7 killed in 120 hours 
18.5 
18.9 
19.5 
44 
72.8 
72 
32 
2 Montenegrin flowers 
5 killed in 120 hours 
36.7 
6 killed in 120 hours. 
40.3 
