UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 771 § 
\ Sao E 
Contribution from the Bureau of Entomology 
L. O. HOWARD, Chief 
Washington, D.C. PROFESSIONAL PAPER February 21, 1919 
A STUDY OF THE EFFECT OF STORAGE, HEAT, 
AND MOISTURE ON PYRETHRUM 
By W. S. Assort, Scientific Assistant 
CONTENTS 
Page Page 
LETUT CLUICG 51010 0s Se ee a oS 1 | Effect of storage in sealed glass containers... 3 
MYCEHOASIONLESHIN GE?) = 52 2s Soci as cintee ean 1 | Effect of soaking in hot or cold water......--. 5 
Effect of exposure to the weather and in a Effect of exposure to dry heat.......-..---.- 5 
TTI cee AS Seer ae eee teem 25) Summanyer Nea: scenester ke osscccincmeeer 6 
INTRODUCTION 
It has been generally accepted by entomologists that pyrethrum 
powder deteriorates rapidly under ordinary conditions of storage, 
but few or no data have been advanced to support this theory or to 
show under what conditions or how rapidly such deterioration takes 
place. The following experiments, made at the testing laboratory 
of the Insecticide and Fungicide Board of the United States Depart- 
ment of Agriculture, Vienna, Va., were conducted to ascertain the 
effect of exposure to heat, moisture, and the weather, and of storage 
in sealed glass containers, on whole and ground flower heads of 
Pyrethrum cinerariaefolium (Trev.). 
METHODS OF TESTING 
Two methods of testing the pyrethrum powder were used: (1) By 
dusting and (2) by dipping. 
In the dusting tests small potted nasturtium plants, grossly 
infested with aphids (Aphis rumicis Linnaeus), were thoroughly 
dusted by means of a small hand dust gun. 
In the dipping tests large specimens of the German roach or Croton 
bug (Blattella germanica Linnaeus) were dropped into a beaker con- 
taining a small amount of the pyrethrum powder to be tested, and 
the beaker was given a shake so that the insects were thoroughly 
covered with the powder. Each roach was then placed in a separate 
8-ounce bottle and observed at frequent intervals, the time when the 
insect became inactive, i. e., unable to walk, and ‘the time of death 
96301°—19—Bull. 771 
