27 
theless present badly spotted fruit. In such cases the additional 
use of some one of the oil sprays may be necessary. 
This wash is of equal value against closely allied scale pests, such 
as Forbes’s scale and the West Indian peach scale, and late sprayings 
are quite effective against the scurfy scale and the oyster-shell scale. 
The spring application, just before the buds swell, has been demon- 
strated by Prof. J. M. Aldrich to kill most of the eggs of the apple 
aphis, and Mr. Fred Johnson, of this Bureau, has found that it is 
equally effective in destroying the eggs of the pear-tree Psylla. It 
is useful against other pests which hibernate about the leaf buds of 
fruit trees, as, for example, the pear-leaf blister-mite and the silvery 
mite of the peach, and in California Mr. Clark has shown that it is 
an entirely satisfactory remedy for the peach twig borer (Anarsia 
lineatella Zell.) . 
In addition to this range of usefulness against insect pests this 
wash has shown itself to be a valuable fungicide, notably for the 
peach leaf curl, sprayed trees being practically immune from this 
disease, so that the cost of treatment in the case of the peach is often 
more than made good by the fungicidal benefit alone. Later experi- 
ence indicates its usefulness also as a winter application for apple 
scab and possibly for other plant diseases. 
TIME TO SPRAY FOR SUCKING INSECTS. 
For the larger plant-bugs and the aphides, or active plant-lice, and 
all other sucking insects which are present on the plants injuriously 
for comparatively brief periods, or at most during summer only, the 
treatment should be immediate, and if in the form of spray on the 
plants, at a strength which will not injure growing vegetation. 
For scale insects and some others, as the pear Psylla, which hiber- 
nate on the plants, two or more strengths are advised with most of 
the liquid insecticides recommended, the weaker for summer applica- 
tions and the more concentrated as winter washes. The summer 
washes for scale insects are most effective against the young, and 
treatment should begin with the first appearance of the larve in the 
spring or any of the later broods, and should be followed at intervals 
of seven days with two or three additional applications. The first 
brood, for the majority of species in temperate regions, will appear 
‘during the first three weeks in May. Examination from time to 
time with a hand lens will enable one to determine when the young 
of any brood appear. 
The winter washes may be used whenever summer treatment can 
not be successfully carried out, and are particularly advantageous in 
the case of deciduous plants with dense foliage which renders a thor- 
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“See Bul. 46, Bur. Ent., p. 54. 
127 
