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28 BULLETIN 1357, U. S. DEPARTMENT OF AGRICULTURE 
SPRAYING WITH ARSENICALS 
Ordinarily arsenicals used as stomach poisons are the standard 
remedies applied in combating such ravenous leaf feeders. For 
this reason preliminary tests were made with varying strengths of 
calcium arsenate, arsenate of lead, and Paris green. In spraying 
the plants at Alexandria, Va., with a pressure sprayer, special 
care was taken to cover all of the foliage so that it presented a 
whitewashed appearance which lasted many days. The arsenates 
of lead and calcium did not injure 
the rose foliage when used at the 
rate of from 2 to 214 pounds to 50 
gallons of water, to which one-half 
ounce of soap was added for each 
gallon of spray material, provided 
they were apphed only on bright 
days; otherwise severe burning re- 
sulted. This was demonstrated in 
experiments conducted later at 
Oak Lane, Pa., where one block of 
40 rose bushes sprayed at the fore- 
going dilution on a dark, cloudy 
day showed severe burning and the 
plants shed 50 per cent of the foli- 
age, whereas a similar group 
sprayed on the following day, 
which was clear, suffered no injury. 
In marked contrast with the re- 
ported control of this insect on 
strawberry plants by means of 
spraying with calcium arsenate or 
lead arsenate, it was found that 
under the conditions existing in 
rose houses this treatment was not 
only impracticable and objection- 
able but was actually ineffective. 
It was impracticable because the 
beetles fed at night on the young 
and tender growth, which was 
being forced so rapidly during the 
hot, sultry nights that it on 
not be sprayed frequently enoug 
oe ie | Mand. canoer to keep he new foliage covered 
found ene dy ete aa came; thes poison. “sNigkeawen ye the 
whitish deposit which remained 
on the leaves after spraying was objectionable to the florists, be- 
cause it reduced the market value of the cut flowers. It was ineffec- 
tive in controlling the beetles because they avoided feeding on the 
arsenate-coated foliage but continued to devour the new leaves. 
There is, however, one period in the culture of roses when the 
use of an arsenical as a spray has proved effective against the 
beetles. When the rose plants are cut back (fig. 11) practically all the 
foliage is removed and the fresh growth develops frora new buds. 
The absence of foliage forces the beetles to feed on the green bark 
as well as on the swelling and breaking eyes or buds, which causes 
