68 ANNUAL REPORTS OF DEPARTMENT OP AGRICULTURE, r 
The firsl Bamplee were taken booh after spraying, the second samples 
8 days Later. The deposits of methoxychlor and DDT averaged 5.3 
and 7.5 micrograms per square centimeter after spraying and 2.4 and 
-}.•_: micrograms per square centimeter 8 days Later. 
At Yakima. Wash., numerous analyses were made of residues of 
DDT, parathion, methoxychlor, EPN, and malathon on apple foliage 
and iii i it samples from experimental plots, immediately after spray- 
ing and at intervals thereafter. The same rate of initial deposit and 
weathering was again obtained for DDT, parathion, EPN, and 
methoxychlor. Malathon. a more recently introduced insecticide, 
showed about the same rate of weathering as parathion, 30 bo 50 per- 
cent of the initial deposit being lost during the first -_M hours after 
spraying. No malathon was found on the apples at harvest. 
In further residue analysis experiments at Yakima it was found 
that wet table powder suspension sprays gave somewhat higher initial 
deposits on apples, pears, and peaches than comparable amounts of 
malathon applied in emulsion form. There was little or no residue 
at harvest in either case. The residues on peaches were higher 
initially and weathered off more slowly than on apples or pears. 
Ethylene Dibromide To Be Field-Tested for Eiiglemaim Spruce 
Beetle Control 
Formulations of ethylene dibromide in emulsions and fuel oil solu- 
tions were tested against the Englemann spruce beetle. They showed 
sufficient promise in small-scale tests to justify Larger-scale te-t inf- 
ill cooperation with the Forest Service. The resulting control will 
be compared with that obtained by application of the standard ortho- 
dichlorobenzene-No. 1 fuel oil solution. 
Aerosol Formulations Tested for Licensing 
All aerosol formulations proposed during the year by manufac- 
turers for commercial production under United States patent 
2,321,023, which Is assigned to the Secretary of Agriculture, were 
examined for chemical compatibility, stability, and Lnsecticidal effec- 
tiveness. Approval was issued for 52 of these which met established 
standards. 
Another Aerosol Developed for Greenhouse Use 
Experiments with schradan | octamethyl pyrophosphoramide) aero- 
sola For use in greenhouses showed that this insecticide is effective 
the control of Bpider mites and aphids on ornamental plant-. 
Difficulties were encountered with nozzle stoppage in such aerosols 
because most commercial lot- of schradan reacted with the walls of 
the iron aerosol cylinders t<> produce a heavy sludge. It was found 
that this reaction could be eliminated by washing the schradan with 
dilute -odium bicarbonate solution. All schradan now being supplied 
by the manufacturers for aerosol use is washed in tin- way and dried. 
Improved Aerosol Valve Designed 
An improved type of aerosol valve w n s designed to incorporate a 
protective diaphragm thai prevents contact of solvents and propel- 
lent with the rubber valve part-- during storage prior to use. This 
