BUREAU OF ENTOMOLOGY AXD PLANT QUARANTINE 9 
inclusion of phenyl ethyl alcohol in the formula was found to interfere 
somewhat with the stabilizing action of the eugenol. 
By a recently developed method for the biological assay of soils 
that have been treated with lead arsenate for grub control, soil from 
various points in the Middle West, where "l,000 pounds of lead 
arsenate had been applied a few years ago for grub control, appeared 
to contain the equivalent of 675 to 800 pounds of freshly applied 
lead arsenate, indicating a reduction equivalent to the loss of 200 
to 325 pounds of lead arsenate. A basic zinc arsenate was found to 
be only slightly toxic to Japanese beetle larvae. 
An investigation on the use of hydrocyanic acid gas as a fumigant 
for adult Japanese beetles in refrigerator cars was completed, and 
the dosage requirements for the fumigant at various temperatures 
from 45° to 75° F. were worked out. A method has been developed 
for forcing paradichlorobenzene gas rapidly through the soil of balled 
and potted plants to control the grubs of the Japanese beetle. 
The studies of Japanese beetle parasites and their colonization 
in new areas have been continued by the Moorestown laboratory. 
About 9,500 Tiphia popilliavora Eoh. females were collected in the 
summer of 1938 from 9 established colonies and the material used to 
provide for the liberation of 64 colonies in Maryland, 18 in Connecti- 
cut, and 12 in New York. Efforts to establish the Korean strain 
have been continued, since it is desirable to have a fall parasite species 
that will emerge late enough in the season to parasitize third-instaf 
larvae of the Japanese beetle, thus complementing the work of T. ver- 
nalis, which attacks third-instar host larvae in the spring. In the 
spring of 1939, 145 colonies of T. vernalis Ron. were collected and 
liberated in 6 States. One colony of the dipterous parasite Centeter 
cinerea Aid. was released in Washington, D. C, in 1938, to determine 
the synchronization of this species with its host in a more southern 
area than those in which it had been previously liberated. 
The milky diseases, which have received special attention, appar- 
ently occur rather generally through much of the older heavily in- 
fested area, although they have not been found at points of heavy 
localized infestation on its outer fringe, or at any point in New Eng- 
land. In experimental field plots first started in 1936 very high 
disease incidence and almost complete elimination of grubs have 
occurred. 
Because of the difficulty in propagating these organisms in artifi- 
cial media, it has been necessary to use the bodies of Japanese beetle 
grubs. A micrometer injection block has been developed with which 
2,000 larvae can be inoculated per day. The spores of both type A 
and type B milky disease, after being stored 41 months in dried-blood 
films on glass slides in ordinary wooden slide boxes, gave as high in- 
fection by puncture inoculation as was obtained when the material 
was fresh. 
A method of holding milky-disease material for subsequent field 
work has been developed at the Moorestown laboratory. Diseased 
larvae are ground and mixed with either talc or precipitated chalk, 
and the mixture is then passed through a 100-mesh sieve. The mix- 
Lures may be diluted with water and applied as a spray or mixed with 
soil and broadcast 
