BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 61 
to the effect that cryolite and cuprous cyanide, in either sprays or dust 
mixtures, were the most effective stomach poisons available for use 
against this pest. It was found, however, that although these mate- 
rials give satisfactory control of the pinworms up to the lime of the 
early picking of the tomatoes, the degree of control ranging from 85 
to 90 percent, the numerical abundance of the pest increases so rapidly 
when climatic conditions are favorable that 1 or 2 applications of 
insecticides toward the end of the picking season may be required in 
the presence of intense infestation as a final step in pinworm control. 
Ordinarily, however. 3 or 4 applications of cryolite or of cuprous 
cyanide appear to be sufficient' to control the pinworm if they are 
timed properly. 
The tests of 1938 disclosed that materials such as phenothiazine, 
cube, and derris are of doubtful value in combating the pinworm. 
Biological investigations of the pinworm disclosed that in southern 
California the conditions prevailing during the winter have an im- 
portant relation to the survival of the species, since temperatures below 
freezing increase greatly the rate of mortality, but that the prevalence 
of wet and cool weather during the spring and early summer may have 
such a detrimental effect on the survival of the pinworm moths and 
their rate of egg deposition as to counteract favorable winter 
conditions. 
During the past two or three seasons parasites have become an im- 
portant natural influence in checking the abundance of the pinworm. 
Two species new to science as well as two species not previously known 
to exist in southern California have acted as checks. 
PEA WEEVIL 
Extensive field experiments in controlling the pea weevil, carried on 
in cooperation with the States of Washington, Oregon, and Idaho 
during the year, again demonstrated that dust mixtures containing 
rotenone will protect peas against this pest if the mixtures are applied 
in the way recommended and at the proper time. 
Special surveys in the Blue Mountain area of Washington and 
Oregon revealed that over four times as much dust mixture containing 
rotenone was used against the pea weevil in this area as was used the 
preceding season. In 1937 approximately 47.5 tons of dust mixtures 
containing rotenone, costing approximately $10,925, was used to pro- 
tect peas (about 38.000 acres), whereas in 1938, with an area of approxi- 
mately 34.000 acres in peas, 211.5 tons of dust mixtures containing 
rotenone, costing approximately $37,780, was used. The general 
results of the control campaigns were nearly the same, since 716 acres 
of peas, constituting 1.9 percent of the total acreage, were discarded in 
1937 on account of pea weevil damage, whereas in 1938 the area dis- 
carded was 386 acres, or 1.1 percent of the total acreage. The decided 
success attained against the pea weevil during preceding seasons by 
the use of dust mixtures containing rotenone led to a further intensifi- 
cation and increased use of this materal during the spring and early 
summer of 1939. As illustrating the extensive use of this insecticide 
it may be stated that one canning company in Washington used approx- 
imately 150,000 pounds of the dust mixture costing about $6,000. More 
over, some of the larger canning companies have adopted the policy 
of preparing their own dust mixtures rather than purchasing commer- 
