2 
ment, the value of which has been demonstrated by much practical 
experience, an orchard can be protected from serious injury and kept 
in a good paying condition so far as influenced by the San Jose scale. 
In view of the above, it is certainly very unwise and wasteful to dig 
up and burn a large portion of an orchard because it is infested with 
this scale insect, especially since the replanted stock, even if clean 
when purchased, would, with little doubt, be in the same condition of 
infestation in a very short time. 
One of the main objects of this circular, therefore, is to emphasize 
the importance and value of honest efforts to control this insect for the 
great majority of districts where it has established itself, rather than 
efforts at extermination, which will at best rarely prove successful and 
will always be accompanied with great immediate loss. The other 
principal object is to designate briefly the means of control which 
experience has shown to be of practical value. 
THE DIFFERENT MEANS OF CONTROLLING THE SAN JOSE SCALE. 
The methods of control which have been especially followed in the 
Eastern States are (1) the lime-sulphur wash, (2) the soap treatment, 
(3) treatment with pure kerosene, (4) treatment with crude petroleum, 
(5) treatment with mechanical mixtures of either of the last two oils 
with water, and (6) petroleum emulsion with soap. All of these methods 
have proved themselves to be successful against the San Jose scale when 
properly carried out. As compared with the lime-sulphur wash the next 
three mentioned are much more expensive, and the two oils, unless very 
carefully applied, are more likely to injure the treated plants. They are, 
on the other hand, more certain to effect nearly or quite complete 
extermination of the scale. One’s choice of method must therefore be 
governed by availability, special needs, and experience. In the main 
these remedies, including the lime-sulphur wash, are winter treatments 
and may be employed at any time when the trees are in dormant, leaf- 
less condition. The weaker oil-water mixtures and the emulsions may, 
however, be used in the growing season. The treatments enumerated 
are all for trees in the orchard. Nursery stock badly enough infested 
to require such treatment is best destroyed. For the general disin- 
fection of nursery stock the hydrocyanic-acid-gas treatment is the 
standard and only satisfactory means. 
The lime-sulphur wash.—-In California, where this scale insect first 
occurred, the standard remedy for it is the lime, sulphur, and salt wash, 
a mixture formerly used as a sheep dip in Australia and employed with 
little change against the San Jose scale and, by a lucky chance, proving 
effective. This wash was naturally first thought of on the discovery of the 
San Jose scale ineastern orchards. The earlier tests, however, conducted 
by this office in 1894, were unfavorable, and the experimentation which 
followed resulted in the demonstration by ourselvesand others of several 
