6 CIRCULAR 920, U. S. DEPT. OF AGRICULTURE 
where it could be easily observed. Therefore, the first inspections were 
limited to host plants in yards and spot examination of other plants near 
buildings and roadways on properties outside the intensive-inspection 
zones. Every property within the area was inspected in this manner. 
The owner of the property was questioned to find out whether he had 
received Plant Garden material and if he had his property was scheduled 
for future reinspection. 
In reinspections, hosts from the Plant Garden, as well as adjacent hosts, 
were included. If the Plant Garden hosts had been removed, all host plants 
within approximately 50 feet of the former location were checked. If the 
owner did not have any information on the location of the host plants, 
every host on the property was examined. Two infested areas where 
scales were not found in the first inspection were located by reinspection 
of properties of recipients of suspected material. 
As inspection progressed, it was found that the build-up and spread of 
the scale were slow, that natural spread was limited to the immediate 
vicinity of infestations, and that any infestation found outside this restricted 
area would probably be due to movement of infested material from the 
garden. Therefore, the original plans with reference to inspection of 
properties near known infestations were modified. The probable area of 
natural spread was redefined to include the area within 4 mile of known 
infested properties. Within this area orchards adjacent to infestations 
were given a tree-to-tree inspection and at least one-fourth of the trees in 
other orchards were inspected. Inspections were made from the ground 
and from ladders, and were supplemented by microscopic examination in 
the laboratory of large numbers of randomly collected twigs. This pro- 
gram was carried out at least twice in much of the intensive inspection 
areas 
Until the discovery of a long-standing infestation near Bidwell Park in 
1949, natural spread appeared to be limited to properties adjacent to pre- 
viously infested properties. In the Bidwell Park area infestation were 
found more than }4 mile from any other infestation. The intensive inspec- 
tion was then Sed to include the area within 1 mile of all known 
infestations. The intensity of inspection outside the \4-mile area previously 
inspected, varied with the degree of the earlier infestation and the time since 
the area had been put under treatment. In Chico and nearby towns every 
host plant was inspected. 
The U. S. Bureau of Plant Industry furnished a list of all shipments of 
host material from the Plant Garden made from 1928 to 1934. Shipments 
made during these 6 years were selected as representing a large sample of 
the material sent out. They contained material most likely to be infested, 
since the infestation could be expected to increase from the time of estab- 
lishment until discovery in 1934. All the material that could be located 
in the Pacific Coast and adjacent States and in the Gulf States was inspected 
with negative results. These regions were selected as the ones likely to 
be most favorable to the establishment of new infestations. The ento- 
mologists of the States concerned cooperated in this work, and some of the 
inspections were made entirely by State personnel. Inspections in Calli- 
fornia were made by County, State, and Federal employees. 
