54 HYDKOCYAXIC-ACID GAS FUMIGATION IX CALIFORNIA. 
severely infested with purple scale, was fumigated with the 1-1-3 
formula with an exposure of one hour. Dosages varying from 1J 
to 2^ oimees per 100 cubic feet were used. The result was that 
eradication occurred on the leaves and branches at a rate of 2 oimees 
per 100 cubic feet, thus corroborating the work on such small trees 
previously carried on at Orange. 
Eradication of an insect would be preferable, yet experience during 
these experiments just mentioned demonstrated that the dosage 
required for eradication might result in injury to the fruit. A rate 
of 1 ounce per 100 cubic feet for trees about 11 to 12 feet high was safe 
under almost all conditions and such a rate was adopted for general 
work. Dosage schedule Xo. 1. based on such a strength of gas, was 
prepared at this time. 
This schedule Xo. 1 was used during the autumn of 190S by several 
practical outfits in the vicinity of Whittier, and has since been fol- 
lowed in other sections in which the purple scale occurs. Thousands 
of acres have been fumigated after this schedule. The general result, 
when the work has been carefully done, has corroborated the writer's 
own experiments in that all live insects and in excess of 99 per cent 
of the eggs were destroyed on the leaves and branches. Such a 
killing is entirely satisfactory. In some cases a slight amount of 
pitting of fruit has occurred, especially in the top of the trees, and has 
caused some growers to complain. This slight amount of pitting can 
be OA'erlooked by reason of the superior killing which has resulted. 
To use a dosage sufficient to control the scale and at the same time 
entirely avoid pitting throughout a fumigating season is a practical 
impossibility. 
The first season the improved system of fumigation was adopted 
schedule Xo. 1 was used almost universally. As this schedule gives 
dosages considerably in excess of those formerly used, fumigators in 
general became somewhat uneasy about using it, with the result that 
during the season of 1909 a three-fourths schedule, rather than full 
schedule No. 1. was used by the majority of outfits. Although the 
results with the three-fourths schedule have been very good, this 
schedule is far less satisfactory than the full schedule Xo. 1. 
The writer advises the use of fidl schedule No. 1 (see fig. 9. p. 
for the purple scale. The results with this dosage are so superior, as 
shown by experience, that most orchards are rendered so clean that 
thereafter they do not require fumigation oftener than once in two 
years. It is more economical to use schedule No. 1 and escape tr 
ment alternate years even if a little fruit is pitted in the operation 
than to use a smaller dosage and be obliged to treat an orchard every 
year. It is seldom, however, that any marked degree of pitting takes 
place with schedule Xo. 1. if proper care is exercised during the 
operation. 
