BULLETIN 
As will be noted in Table II, the powders ground in 1912 were 
ineffective in 1918, when tested against nasturtium aphids. Whole 
flower heads from the same stock, which had been kept in sealed 
fruit jars for 5J years and were ground in 1918, killed from 80 to 
90 per cent of the treated aphids. Fresh pyrethrum tested at the 
same time killed 90 per cent. 
Table III gives the results of dipping tests against roaches with 
the same materials as used in Table II. In every case the powders 
ground in 1918 Were found to be effective, all of the roaches being 
killed in from 32 to 40.3 hours, while in no case did the powders 
ground in 1912 kill all of the dipped roaches in 120 hours. Fresh 
pyrethrum, used at the same time, required on the average 31.3 
hours to kill 10 roaches. These tests show that pyrethrum powder 
kept in tightly stoppered bottles for 5J years loses practically all of 
its effectiveness, but that the unground flower heads stored under 
the same conditions for the same length of time are practically un- 
hurt. 
Table IV shows che effect, on powdered flower heads, of 5^ years' 
storage in tightly stoppered bottles or sealed glass fruit jars. 
Table IV. — A comparison of the effectiveness against nasturtium aphids of freshly 
ground Dalmatian closed flower heads and of the same powder after it had been stored 
in tight glass containers for 5\ years. One nasturtium plant, grossly infested with 
dusted for each test 
Material. 
Crop 
of— 
Dalmatian closed flower heads ground in spring of 1912. 
No. 
Tested November, 1912. 
Tested March, 1918. 
Num- 
ber of 
tests. 
Length 
of 
tests. 
Results. 
Num- 
ber of 
tests. 
Length 
of 
tests. 
Results. 
1 
2 
3 
4 
5 
Wild flowers 
do 
do 
Cultivated flowers. . . 
do 
do 
1908 
1909 
1910 
1908 
1909 
1910 
1 
2 
2 
2 
2 
12 
Days. 
1 
2 
4 
2 
2 
1 
98 per cent killed. . 
95-100 per cent 
killed. 
99 per cent killed. . 
100 per cent killed. 
do 
do 
4 
2 
2 
4 
2 
2 
Days. 
7 
7 
7 
7 
7 
Inefiective. 
Do. 
Do. 
Slightly effective. 
Inefiective. 
Do. 
1 The cabbage aphis {Aphis brassicae Linnaeus) was used in these tests. 
The materials used in these tests were received in 1911 as whole 
flower heads, which were ground and sifted in the spring of 1912, 
and stored in sealed fruit jars or tightly stoppered bottles. These 
powders were tested against nasturtium aphids in November, 1912, 
and again in March, 1918. 
As will be noted, all of these powders were found to be effective 
in November, 1912, and of almost no value in March, 1918. It is 
therefore evident that pyrethrum powder stored in sealed glass con- 
tainers for 54- years wil 1 lose practically all of its efficiency. 
