EFFECT OF STORAGE, HEAT, AND MOISTURE ON PYRETHRUM 5 
In connection with the deterioration of unground flower heads, it 
is of interest to note that, in the 1912 tests, practically no difference 
in effectiveness was found between the 1908, 1909, and 1910 crops, 
which indicates that the flower heads are not noticeably injured in 
four years under the commercial conditions of storage. 
EFFECT OF SOAKING IN HOT OR COLD WATER 
Table V shows the effectiveness against roaches of pyrethrum pow- 
der which had been soaked for 24 hours in hot or cold water. 
TaBLe \.—LEffectiveness against roaches of pyrethrum powder soaked for 24 hours in 
hot or cold water. Ten roaches dipped in each test 
Hours required to kill. 
No. Treatment. 
First roach.| Lastroach.| Average. 
Pe ROOK UTIL OR LOA 3 oo si2 13 e laa) '= (ah is caja ate sjain im my/s aeons Se 21.7 35.9 25.9 
PE SULK OGM COLGUWAbET cc = o.. te Sa yen oo heen ad nicle ce ee ee ee 21.9 48.2 38.9 
Doon liseakede nou Watenes: . 255.9. oc seb aces sees oot eee eesoee 12.5 | 1 living at end of 94 
hours. | 
1 Probably injured in dipping. 
The material used in test No. 1 was prepared by soaking 20 grams _ 
of pyrethrum powder (80 mesh) in 100 c. c. of cold water for 24 hours. 
The water was then filtered off and the powder dried at room tem- 
perature and resifted to 80 mesh. 
The material used in test No. 2 was prepared in the same way, 
boiling water being used. 
This table shows that pyrethrum soaked for 24 hours in cold water 
killed all of the dipped roaches in 48.2 hours, but required on the 
average 13 hours longer to kill than did the untreated powder. The 
pyrethrum treated with hot water killed only 9 roaches in 94 hours. 
It is therefore evident that cold water removes some of the active 
ingredients from pyrethrum powder, but not as much as is removed 
by hot water. 
EFFECT OF EXPOSURE TO DRY HEAT 
Table VI shows the effect on ground flower heads of exposure to 
dry heat for 18 hours. 
Taste V1.—Effectiveness against roaches of Benne powder exposed to dry heat for 
18 hours. Ten roaches dipped in each test 
Hours required to kill. 
No. Temperature. 
First roach,| Last roach.| Average. 
MOY CUGC  TMNORLO oo52.5 +210 vere cae nade demons + (aoa eMin » oeuleelairie 20.5 39.6 31.0 
Ad Dll i DS slice ne sovaraweO tide «oats camer 19.6 43.6 30.9 
ei ee tek bh Sob ch bs beleive be > apnea anes «+m ms step aa 21.1 47.4 27.8 
MIO Re sn oe oa OE vnnec coco Cele ccuse awit > + <a e Serene 1 dead in 48 hours, 
BP IAOUC, 222022 ed Oe RS ee Oe Ree Fee ae dat dead in 48 hours. 
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