BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 23 
About 50 percent of those treated with either iy 2 pounds of copper 
sulfate, 1% pounds of zinc chloride, or % pound of sodium arsenite 
per cubic foot were still serviceable. Treatments applied in the spring 
of the year were much more effective than those applied in late summer 
or early fall. 
Soil Poisons Developed for Termite Protection 
DDT and BHC are being studied with a view to preparing formula- 
tions of each that will provide protection from termites for 10 years 
or longer when used as a soil poison. In Mississippi, 8 percent of DDT 
in fuel oil continues to give effective protection 8 years after its appli- 
cation ; also sufficient BHC to give 0.8 percent of the gamma isomer in 
kerosene has given complete protection for 6 years. Tests with chlo- 
dane, dieldrin, and aldrin show that these materials are also effective 
as soil poisons for termite control. 
Termite Treatment Developed for Wallboard and Insuation 
Panels 
Samples of wallboard and insulation panels made of wood pulp or 
agricultural waste, treated with 10-percent sodium arsenite and 2- 
percent copper naphthenate, were only lightly attacked by termites 
and decay organisms after 4 years of direct contact with the soil. 
Untreated samples were very susceptible to termite injury, and were 
heavily damaged in 1 year. 
Spray Reduces Feeding of Dutch Elm Disease Vector 
A 9-percent methoxychlor residual spray, applied with a mist 
blower, may be fully as effective in preventing feeding by the smaller 
European elm bark beetle — one of the carriers of the Dutch elm 
disease fungus — as a 12-percent DDT emulsion residual spray. This 
was shown by spray tests performed in the District of Columbia, in 
cooperation with National Capital Parks, United States Department 
of the Interior. There was nearly 100-percent reduction in feeding 
for 100 clays after either type of spray was applied, and about 70-per- 
cent reduction for 150 days. 
Several of the newer insecticides were tested in separate small- 
scale tests at Columbus, Ohio, for residual control of the smaller 
European elm bark beetle. For 68 to 75 days after spraying, formula- 
tions of methoxychlor, dieldrin, TDE, and DDT were almost com- 
pletely effective in preventing feeding. 
Special Device Converts Helicopter to an Airborne Mist Blower 
What is in effect an airborne mist blower has been developed for 
control of the smaller European elm bark beetle. This consists of 
a new type of spraying device attached to a helicopter. In tests at 
Medfield and Norwood, Mass., in cooperation with an airline, the 
Massachusetts Department of Conservation, and the Connecticut Agri- 
cultural Experiment Station, it was found that as good results could be 
obtained with this device as with hydraulic sprayers. Helicopter 
sprayers provide heavier deposits in the tops of trees than do hy- 
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