FUMIGATION OF CITRUS TEEES. 63 
efficiency between December and April, provided the work be per- 
formed by careful men who observe the various factors affecting 
these two considerations. These factors are given at various places 
throughout this bulletin. 
FUMIGATION FOR THE MEALY BUG. 
Considerable excitement has been aroused in some parts of southern 
California during the last year or so over a so-called threatened 
invasion of the citrus mealy bug (Pseudoeoccus citri Risso) . This 
insect has been known in this region for at least 15 years. Its 
greatest injury has been done in the vicinity of National City, San 
Diego County; along the Sierra Madre foothills, near Monrovia, Los 
Angeles County; and very recently at Santa Paula, Ventura County. 
There have also been sporadic occurrences in many other sections. 
This sporadic activity has been of a somewhat puzzling nature. A 
tree severely infested with the mealy bug one day might be found to 
be practically free of this insect a month later, though no artificial 
measures of control had been applied. The mealy bug might reap- 
pear on this same tree the following year, or even sooner. The 
writer is inclined to attribute this disappearance largely to the 
activity of parasitic and predaceous insect enemies. The general 
appearance of the remains of the mealy bug, as well as the rear- 
ing of several beneficial insects therefrom, including two or* three 
species of Hymenoptera, a brown lacewing (Hemerobius sp.), and a 
syrphus fly, lead the writer to this conclusion. Several species of 
Coccinellidse also have been found present in severe infestations of 
this insect. Undoubtedly climatic conditions as well as fungous and 
bacterial diseases produce some effect. 
The recent prominence of this insect in the immediate vicinity of 
Santa Paula, Ventura County, is well worthy of mention. Its infes- 
tation here has been so severe that the proportion of fruit in some 
orchards ruined by this insect during 1909 was very great. The 
large amount of damage caused there, together with the difficulties 
experienced in destroying the mealy bug, has led to agitation for its 
control in several other localities. 
At various times during this investigation a few trees infested with 
mealy bugs have been treated. The usual dosage has been 1^ to 2 
times schedule No. 1. The results have been variable. Some trees 
would appear to be entirely freed, while on others many live insects 
would remain. 
During the autumn of 1909 a prominent orchardist of Santa Paula 
carried on some very extensive fumigation work against this insect, 
partly according to the writer's directions. Some trees were treated 
with 2, 2 1, and 3 times schedule No. 1 for from one to one and one- 
half hours without eradicating the scale in any case. The results 
