UNITED STATES DEPARTMENT OF AGRICULTURE 
DEPARTMENT BULLETIN No. 1332 
Washington, D. C. T May, 1925 
EMULSIONS OF WORMSEED OIL AND OF CARBON DISULFIDE 
FOR DESTROYING LARVAE OF THE JAPANESE BEETLE IN THE 
ROOTS OF PERENNIAL PUNTS ' 
By B. R. Leach, Associate Entomologist, and J. P. Johnson, Junior Entomolo- 
gist, Fruit Insect Investigations, Bureau of Entomology 
CONTENTS 
Page 
The plants concerned 1 
Preliminary work 2 
Oil of wormseed (American) 3 
Wormseed-oil emulsions 4 
Toxi city of wormseed-oil emulsions 7 
Application to larvae in soil and plants 9 
Value of wormseed oil as an insecticide 12 
Treatment of peony roots 12 
Page 
Carbon-disulphide emulsions 13 
Toxicity of carbon-disulphide emulsion to 
larvae.-. 14 
Application of carbon-disulphide emulsion to 
larvae and peonies 15 
Commercial use of emulsions 15 
Summary and conclusions 16 
Literature cited 17 
THE PLANTS CONCERNED 
Japanese iris (Iris Icaempferi), 2 peonies (Paeonia spp.), and per- 
ennial phlox (Phlox spp.) are all extensively grown in and near the 
area infested by the Japanese beetle, Popillia japonica Newm. The 
acreage of these crops in nurseries growing miscellaneous perennial 
stock is considerable, and there are also nurseries of considerable 
size specializing in iris and peonies. 
These three plant species are essentially different from each other in 
root structure. The roots of Japanese iris (fig. 1) are an impene- 
trable mass of coarse fibers interspersed with small quantities of 
soil and emanating from a hard, thick rootstock or crown. Larvae 
of the Japanese beetle are found in this mass of roots and soil close 
up to the crown, and can be discovered and removed only by cutting, 
which is an obviously impractical method. The roots of perennial 
phlox, while coarse and heavy, are not matted to any great extent 
except when the soil is wet at the time of digging in November, 
but this condition prevails in two out of every three years in New 
Jersey and it is then difficult to remove any larvae present except 
by washing. This operation appreciably injures the roots. In the 
case of the peony, the root structure is tuberous with many cavities 
mostly formed underground by the flower stems of the previous 
1 The writers are indebted for assistance rendered by J. W. Thomson and W. E. Fleming, investigators, 
New Jersey State Department of Agriculture. 
» It is fairly probable that the Japanese beetle entered the United States in the larval form in the roots 
of iris from Japan. 
31469°— 25t 1 
