350 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1944 
syrups, often with added aromatic chemicals, although not accom- 
plishing their original purpose of direct control, have been found 
valuable aids to the timing of spray applications, by giving informa- 
tion on moth activity and abundance in the orchard. 
SPRAY-RESIDUE PROBLEM 
In the earliest official test of arsenicals (Cook, 1880) the question 
of the effect of the material on the consumer was considered. On the 
basis of analyses which were made at that time, the conclusion was 
reached that the quantity of poison that could be carried over to har- 
vest as a result of the spraying was insignificant. With the type of 
spraying that was done in the early days this was probably a correct 
conclusion. However, as the number of spray applications increased, 
along with increases in the strength of the spray mixture, and in the 
number of gallons applied per tree, the quantities of lead and arsenic 
on the fruit at harvest constantly increased. The question of dan- 
gerous residues was raised from time to time but it was usually dis- 
missed with a statement that it would be necessary to consume an 
impossibly great quantity of the product at one sitting to obtain an 
injurious dose. During all this period the acute toxicity was the only 
consideration, but in the early 1920’s there developed a realization 
that the use of lead arsenate sprays had increased to a point where 
American fruit was carrying quantities of residue actually or poten- 
tially dangerous to human health from a cumulative standpoint. The 
situation was crystallized in 1925, when British health authorities 
rejected shipments of American apples because of excessive arsenical 
residues. This episode was followed by appropriate action by the 
United States Department of Agriculture in carrying out its responsi- 
bility for the enforcement of the Food and Drugs Act. This action 
caused consternation in the apple industry, but fortunately effective 
washing methods and machinery were promptly developed for re- 
moving the residue before the fruit is marketed, which has permitted 
the continued employment of lead arenate until other less objection- 
able insecticides or other methods of control are developed. 
SEARCH FOR NEW INSECTICIDES 
The difficulties with spray residues and with worm control in some 
localities have led to an intensive search for better and less objec- 
tionable insecticides. This search has already proved productive. 
Cryolite is effective in the Pacific Northwest, although it is undepend- 
able elsewhere, and its use involves something of a spray residue prob- 
lem and in many cases washing the fruit is necessary. Nicotine 
bentonite has been found more effective than lead arsenate in certain 
parts of the Middle West and is used to a considerable extent there 
