23 
This wash is of value also as a fungicide, protecting stone fruits from 
leaf fungi, and is also a protection against birds, the common California 
linnet doing great damage to buds in January and February. The 
wash is almost invariably made and applied by contractors, and costs 
about 5 cents per gallon applied to the trees. 
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 applications 
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 of 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 thorough 
wetting difficult in summer, or with scale insects which are so irregu- 
lar in the time of disclosing their young that many summer treatments 
would be necessary to secure anywhere near complete extermination. 
In the winter also, with deciduous trees, very much less liquid is 
required, and the spraying may be much more expeditiously and thor- 
oughly done. In the case of badly infested trees, a vigorous pruning 
is advisable as a preliminary to treatment. 
As winter washes for temperate regions the kerosene washes and 
whale-oil soap solutions have so far given the best results. In the 
growing season any of these stronger washes would cause the loss of 
foliage and fruit, and the more concentrated probably the death of the 
plant. 
THE GAS TREATMENT. 
The use of hydrocyanic-acid gas originated in southern California in 
work against citrus scale insects, and was perfected by a long period of 
experimentation by an agent of this division, Mr. D. W. Coquillett. 
It is undoubtedly the most thorough method known of destroying scale 
insects and especially is it the best treatment for citrus trees, the abun- 
dance of foliage and nature of growih of which renders thorough spray- 
