58 HYDROCYANIC-ACID GAS FUMIGATION IX CALIFORNIA. 
the red scale in orchards and yet these have become reinfested within 
a year. In one orchard the reinfestation was traced to some fig trees 
on one side which had not been fumigated; in another, the scale 
spread from a neighboring orchard across the way; while in a third, 
the scale came from nightshade (Solarium sp.) which had not been 
destroyed. The insect is distributed by the wind, b}^ birds, and 
especially by clinging to the bodies of the hordes of insects which 
frequent citrus trees and carry them to other trees. Foremost among 
these insects are the ladybirds (Coccinellida?), of which there are 
numerous species as well as vast quantities of individuals. Before 
fumigating for the red scale care should be taken that host weeds 
along irrigation flumes, ditches, and fences are destroyed so far 
as possible and all neighboring trees subject to its attacks cleaned up. 
Dosage. — The first orchard treated for the red scale (December, 
1907) was a severely infested one of between 2 and 3 acres of trees 
in an unhealthy condition, and was located at Sierra Madre. The 
height of the trees was about 10 to 14 feet. The 1-1-3 formula 
was used. Exposure lasted one hour. Dosages of from one-half 
to 3 ounces per 100 cubic feet were used. Eradication took place 
with all strengths. 
In September, 1908, about 1 acre of trees about 10 feet tall, 
located at Whittier, was treated with dosages of from of 1 to 1| ounces 
per 100 cubic feet. Exposure lasted one hour. Eradication resulted. 
During April, 1909, 4 to 5 acres of unhealthy orange and lemon 
trees at Villa Park, Orange County, were fumigated with dosages of 
from one-half to 1| of schedule No. 1. The exposures lasted 45 
minutes, 1 hour, and 1J hours. Complete eradication occurred. 
An acre of entirely healthy orange trees severely infested with the 
red scale — fruit as well as leaves and branches — was treated during 
September, 1909. The results of this experiment showed that a 
one-half schedule usually would destroy the scale on the leaves and 
branches, but that it required a three-fourths schedule to accomplish 
this on the fruit. As satisfactory work was done with an exposure 
of 45 minutes as with 1 hour. 
The examination of much work carried on by practical outfits using 
both a three-fourths schedule and a No. 1 schedule has demonstrated 
that eradication would result when careful work was done. 
Results from these extensive observations show that the red scale 
is more easily destroyed on unhealthy than on healthy trees, and 
that it is slightly more difficult to destroy on the fruit than on the 
leaves and branches. The dosage used must be based on a strength 
sufficient to destroy the scale on all parts of all trees; thus it is 
apparent that a three-fourths schedule is the most economical for 
the red scale. In all fumigation work against this insect it is advised 
that a three-fourths schedule (three-fourths of schedule Xo. 1) (see 
fig. 11) be used. An exposure of 45 minutes is sufficient. 
