FUMIGATION OF CITRUS TREES. 57 
purple-scale eggs than all the rest of the tree, and on the hatching 
of these eggs the insects will spread to other parts of the tree. The 
danger from old scaly fruit is evident, and all such should be re- 
moved from the trees before fumigating an orchard. 
There are times in which a scale-infested orchard to be treated 
contains some scale on the green fruit. During the autumn season 
when fumigation is most practiced the purple scale is largely in its 
earlier stages of development, in which it may be destroyed by the 
employment of schedule No. 1. The immature fruit which is scale 
infested can be left on the tree. It is the old scaly fruit which requires 
removal at the time of fumigation. 
TWO SUCCESSIVE TREATMENTS. 
A few growers whose groves are severely infested with the purple 
scale will desire to have the scale eradicated if possible, even though 
the initial expense is considerably above the cost of a regular treat- 
ment, yet they do not care to assume the risk of having any fruit 
on the trees injured. In such cases some authorities advise two 
successive treatments during the early autumn and about five or six 
weeks apart. The dosages used should be sufficient to destroy the 
mature insects. The first treatment would destroy all the insects, 
leaving only eggs on the trees. The time elapsing between this and 
the second treatment should be just long enough to allow all the eggs 
to hatch. About five weeks is supposed to be sufficient unless the 
weather be exceptionally cool. Careful inspection will settle this 
point. If the first treatment has been thorough and there are no eggs 
present at the second, eradication should result. A three-fourths 
schedule should be used in each treatment. The first fumigation 
should be in the autumn, not later than the first part of October. 
Double fumigation is seldom resorted to, as its economy in the long 
run is somewhat questionable. 
THE RED SCALE. 
The red scale is generally held as the most difficult of all citrus scales 
to destroy. Extensive experiments during this investigation, carried 
out in many sections of southern California, have proved it to be one 
of the easiest to destroy. It is, however, the most difficult insect to 
keep out of an orchard when once it has become established in a com- 
munity, and this may be the basis for the opinion as to its greater 
resistant power to hydrocyanic-acid gas. By reason of its great pro- 
Mcness, its infestation of some weeds common about citrus orchards 
as well as many trees and shrubs which are sometimes planted on 
driveways or about the buildings on the premises, and the ease with 
which it spreads, this insect frequently will quickly reinfest an orchard 
which has been treated. Live insects left on a few trees in an orchard 
quickly multiply and infest the others. The author has eradicated 
