BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 47 
the United States that had been longest colonized — around Boston, Mass. — 
and these provided adequate material for the releases of 1936, al a cost com- 
paring very favorably with that of the foreign collections. Investigations to 
determine the relation of various coin characteristics to corn-borer resistance, 
including the testing of 130 inbred lines of field corn to determine their suit- 
ability for the development of resistant hybrids for commercial use, have been 
continued in cooperation with the Bureau of Plant Industry. While no plant 
characteristic other than delayed tassel eclosion has been isolated as associated 
with resistance, inbred lines of both held and sweet corn exhibited some resist- 
ance nor associated with the appearance of the tassel. In field-plot and lab- 
oratory experiments in Connecticut the control values of selected insecticides 
and the comparative tolerances of the corn plant to them were determined. 
Results indicated that several insecticidal preparations withstood dilution, 
washing, and wind loss satisfactorily. Spray preparations found to provide 
a high rate of protection against infestation included nicotine tannate, ground 
derris, a high-dispersion nicotine bentonite, and phenothiazine. A dual-fixed 
nicotine consisting of nicotine tannate and nicotine bentonite was found to 
provide a very high rate of protection when applied in a dust form. A prom- 
ising method of preparing nicotine tannate in a paste form which can be used 
in hard water has been developed and is being given field trials of its insecti- 
cidal value. 
Investigations of the corn earworm have been continued in Virginia, Connecti- 
cut, Indiana, and Kansas, and work has been initiated during the year at 
Urbana. 111. Extensive observations were made in Indiana on the relative 
susceptibility of various strains of field and sweet corn to earworm attack. 
Silking and infestation records were obtained on 2,282 plots of dent corn, in- 
cluding approximately 60 varieties, 202 hybrids, and 21 inbreds; and on 422 
plots of sweet corn, including 20 varieties, 71 hybrids, and 18 strains which 
were being studied by the plant breeders for other characters. Although de- 
pendability of the results was reduced by the occurrence of a low infestation, 
a distinct and consistent difference in infestation between varieties was ob- 
served, over and above that due to silking date. There was some indication 
that the quality of resistance, apparently present in certain strains used as 
parents, was transmitted to the hybrid progeny. A series of 14 uniform ex- 
periments on hibernation of the earworm, distributed from the Atlantic sea- 
board west to Kansas, gave definite indications that the earworm, at least 
during the winters of 1934-35 and 1935-36, did not survive in significant num- 
bers north of the thirty-ninth parallel and gives credence to the theory that 
the infestation in the Northern States results from migratory flights from 
southern areas. 
Over 16,000 specimens of insects, belonging to approximately 65 species, col- 
lected on or near corn infected with Stewart's disease, have been cultured in 
an attempt to determine which of these species are responsible for transmitting 
the organism causing the disease. In 1935 three species of beetles yielded the 
causative organism and, in addition to the corn flea beetle, previously recog- 
nized as a carrier, the 12-spotted cucumber beetle gave positive evidence of 
being a carrier of the disease under field conditions. 
Work on the southwestern corn borer in Arizona has been completed, it 
having been determined that barium fluosilicate can be used for the protection 
of especially valuable corn, and that the insect can be controlled under the 
agricultural conditions of Arizona through the proper application of cultural 
practices. A colony of 10,000 Lydella stabulans grisescens, a parasite of 
the European corn borer, was released in Arizona to test its effectiveness 
against the southwestern corn borer. 
CORN INSECTS IN PUERTO RICO 
Tests were made of various insecticides and of mechanical means for con- 
trolling the earworm in Puerto Rico. Certain mechanical methods gave 
excellent control at a cost considered low enough to permit practical use. In- 
secticidal methods, including tests with a number of Insecticides, show that 
barium fluosilicate was the most effective under conditions of the tests Put that 
tins material was not so effective as the mechanical means utilized. 
A study was made of the distribution, bost plants, and life history of the fall 
armyworm under Puerto Rican conditions. Control studies Indicated that 
some benefit could be derived from the application of 1 9 lend arsenate lime dust 
and of barium fluosilicate. Both materials, however, resulted in some burning 
