THE HALL SCALE ERADICATION PROJECT 5) 
in April. The crawlers begin to emerge in April or late in March. A 
further chronology of field observations is as follows: 
Iya ets reap tre NG yee eam etre neta gs first molt 
INO) Sissi resco eens Ansar id late areas en males recognizable 
[eto Pe aie Sa WER cis lnc ES pue hak a ae eR en anette second molt of females; males emerged 
gjUlye2G Mpa nett Pert op, sini ete ele ke gravid females on current growth 
Te OU OTe The Peet es Sea aie a cee gee nearly spent females on current growth 
@ctoletal Gy wks eee hare wane Sek ase sees last crawlers and last males found; live 
scales in all stages present 
Wecember NOM ake ce cr cine eee last gravid females found 
Crawler emergence generally reaches a peak in May or June, before the 
summer sprays are applied. In the absence of a summer-oil spray, emer- 
gence might continue at a high rate throughout the summer. The finding 
of emerged males by June 24, gravid females by July 26, and nearly spent 
females by August 7, all on current season’s growth, shows that there is at 
least a partial second generation in the summer. 
ERADICATION PROGRAM 
When the eradication project was undertaken in 1941, the following 
program was adopted: 
(1) Repeated applications of oil sprays to reduce the scale population on known infested 
properties and decrease the danger of spread while other work was being carried on. 
(2) Survey of the Chico area to locate infestations resulting from movement of host plants 
from the Piant Garden. 
(@) Intensive inspection within 2 miles of known infested properties. This distance was 
tentatively set as the limit of natural spread. As information was developed, it was later 
reduced to 1 mile. 
(4) Location and inspection of host material shipped from the plant garden to points outside 
the Chico area before 1934, when a fumigation procedure for treatment of all hosts being sent 
out of the garden was established. 
(5) Removal of heavy growth along creeks running through infested properties to reveal and 
permit removal and destruction of host seedlings. 
(6) Field tests of oil sprays, both alone and with added toxicants, and of hydrocyanic acid 
gas fumigation, to develop an eradication treatment. As a result, an effective treatment con- 
sisting of fumigation with hydrocyanic acid gas under gastight tents was developed. The 
treatment program includes provision for the following: 
(a) A spring and an early fall spray of light medium oil applied each year beginning 
with the discovery of an infestation, and continuing to completion of the fumigation 
program, to suppress an infestation until fumigation can be started and to supplement 
fumigation during the subsequent treatment period. 
(b) Annual fumigations with hydrocyanic acid gas for 3 consecutive years after the 
last finding of live scales. 
(c) Several annual intensive inspections to check results of treatment after the final 
fumigation. 
SURVEY AND INSPECTION 
All properties in an irregular area approximately 15 miles long and 12 
miles wide surrounding the city of Chico, containing approximately 800,000 
host plants, mostly almonds, were scheduled for inspection. The area is 
isolated from other fruit-growing sections by grain, pasture, and open 
range land. The movement of infested plant material was considered to 
be the most likely means of spread to these properties. 
It was found that any material obtained from the Plant Garden was 
likely to be planted near houses or other buildings or along roadways 
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