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 PLANTS l 



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-oO emulsions 4 



Toxicity 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 



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 Tcaempferi), 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 



> 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 tho larval form in tno roots 

 of iris from Japan. 



31469°— 25f 1 



