BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 
5 
A single application of a spray containing 1 pound of DDT per 100 
gallons gave complete protection to the fruit and foliage throughout 
the entire beetle feeding season of more than 6 weeks. The spray left 
no visible residue on the fruit or foliage and caused no injury when 
used at a concentration of 1 pound in 100 gallons. 
DDT has also been found effective at very low concentrations 
against the grubs of the Japanese beetle in the soil. In a number of 
soil types DDT, when freshly applied at rates of 5 to 27 pounds per 
acre, was as effective as lead arsenate at the rate of 500 pounds per 
acre. Studies in the greenhouse indicated that relatively large quan- 
tities of DDT could be applied to the soil without detrimental effect 
on certain crops, but that others, such as beans, spinach, and toma- 
toes, seem to be unfavorably affected with applications of 25 pounds 
of DDT per aero. 
PEAR PSYLLA SUPPRESSION CONTINUES 
Further progress has been made toward the suppression of the 
pear psylla in the Pacific Northwest. The number of infested prop- 
erties found has continued to decline, 140 being found in 1943 as com- 
pared with more than 1,200 in 1941. Only minor extensions of the 
infested area have been brought to light. In the spring and early 
summer of 1944 one light infestation was found in lower Yakima 
County and several in Benton County, Wash. Three infestations were 
also found in Umatilla County, Oreg., within a few miles of the 
Washington State line. 
The sticky-board trap, mentioned in last year's report, is proving 
a valuable aid in determining the distribution of the pear psylla. The 
board is about 6 by 10 inches, and is covered on both sides with a 
sticky tree-banding material. Yellow boards have captured more 
psyllas than any other color tested. The trap boards have revealed 
light infestations not found by the most careful visual scouting. One 
hundred thousand are being placed this summer at various points in 
the Northwest and elsewhere. Their use will give a much more com- 
plete picture of the infestation than has been possible thus far. 
The spray program continues to reduce the psylla infestation. A 
special study of the effects of the program was made in Spokane 
County, where intensive spraying has been carried on since 1940. 
In 1943 spraying was discontinued in that county, except on prop- 
erties that had been found infested in 1942 or 1943. Thorough 
scouting in the entire county resulted in the finding of only 70 in- 
fested properties, as compared with 889 in 1940 and 466 in 1941. 
Some spraying was done in British Columbia in 1943 and 1944 to 
protect the results obtained south of the border. In some areas co- 
operating growers assisted greatly in the program by applying much 
of the spray material themselves. 
The removal of abandoned pear trees by the Washington State De- 
partment of Agriculture and the grubbing and treatment of pear 
regrowth by both agencies have eliminated many scattered properties 
from the spray program, and in some areas the time required for a 
given coverage has been cut by at least one-half. Considerable quan- 
tities of ammonium sulfamate are being used in the treatment of 
sprouting stumps and regrowth. 
