KM) ANNUAL REPOKTs DE DEPARTMENT OF AGRICULTURE, 194 
compounds. There seems i<> be little possibility of synthesizing the 
pyrethrins I bemselves. 
( 'ertain species of // In rrfuan, including the sneezeweed of the South- 
ern Slate-, were further studied, and ;i new compound called tenulin 
was isolated. The presenee of a very bitter material analogous to 
the (juassiu of quassia wood lead- to the ho])e that HiUniiuu may be 
ii>"<1 in place of quassia, about 1 .<)<)< i.noo pounds of which are im- 
ported annually. 
GeranioL, a rnajor ingredient of .Java citronella oil (from the grass 
( ' [jinlx) [XKjnn n a rd ^is (L.) Rendie). is in wide use for Luring Japanese 
beetles to traps. The commercial materials that are offered in re- 
sponse to purchase orders may meet the specifications drawn up for 
them, and yet differ markedly in their attractiveness. The composi- 
tion of one of the most attractive samples was studied and the iden- 
tified compounds were prepared in pure form and supplied, alone 
or in various mixtures, to cooperating entomologists tot further 
study. There are indications that the specifications for geraniol for 
Japanese beet le traps can be improved. 
DEVELOPMENT OF SYNTHETIC ORGANIC INSECTICIDES 
In tlx 4 attempt to displace objectionable arsenic from its command- 
ing position among- insecticides, some of the many thousands of or- 
ganic compounds now available were studied. Even though there is 
little possibility of synthesizing rotenone or the pyrethrins, which are 
already established as important insecticide-, it i- reasonable to believe 
that other equally valuable compounds may be discovered. Several 
hundred compounds were obtained or made, and submitted to cooper- 
ating entomologists for preliminary testing. Those showing promise 
were made in larger quantities sufficient, in <ome cases, for small 
field tests. Those few compounds that showed sufficient promise 
were studied thoroughly with the idea of finding how to adapt them 
to actual tise. For example, phenothiazine. when prepared in very 
fine form, was found to have superior adherency and toxicity. The 
search for adhesives for this compound was continued, and improve- 
ments in its fungicidal effect were brought about. Kanthone. having 
become commercially available, was included in various spray sched- 
ules for testing, a< was phenazine. which likewise can now be pur- 
< based. 
The toxicity of several hundred organic compounds to codling 
moth larvae was studied in the Laboratory jointly with the Division 
of Fruit Insert Investigations. Only 17 compounds gave 50 percent 
or less of wormy apple plugs. 
SPRAY RESIDUES AND THEIR REMOVAL 
The study of insecticide deposits continued to be the principal 
mean- of comparing spray schedules, methods of application, per- 
sistence through the season, and other variables which may be ex- 
pected to influence the over-all effectiveness of an insecticide. Res- 
ldues of lead arsenate, nicotine, and phenothiazine were studied 
before and after every spraying, and in every plot in which those 
compounds were used at Yakima, Wash., and Vincennes, [ncL, where 
field tests for the development of insecticide- for control of cod- 
ling moth are conducted. At Whittier, Calif., similar studies of 
