FUMIGATION OF CITRUS TREES. 7 
The land on which the orchards occur is for the most part flat or 
only gently sloping, and in a state of frequent tillage — conditions 
which obtain because of the necessity of irrigating during much of 
the year. At Redlands, in San Bernardino County, a considerable 
acreage of oranges is found on terraced land. Fumigation of such 
trees is slow and difficult, but, fortunately, they comprise a very small 
percentage of the groves in that county requiring treatment. 
INSECT ENEMIES OF CITRUS FRUITS. 1 
The larger number of pests most injurious to citrus fruits in south- 
ern California belongs to the Coccidas, a group of insects popularly 
Fig. 1.— Map showing principal localities in southern California where citrus fruits are produced. 
(Author's illustration.) 
known as scale insects. Among the scale insects which are generally 
so destructive as to require extended efforts for their control are the 
purple scale (Lepidosaplies heckii Newm.), the red scale (Chrysom- 
pJialus aurantii Mask.), and the black scale (Saissetia olese Bern.). 
The yellow scale (CJirysompJialus citrinus Coq.), considered a variety 
of the red scale, is much less destructive generally, though sufficiently 
troublesome in some localities to be considered a pest of primary 
importance. The citrus mealy bug (Pseudococcus citri Risso) has 
recently been very injurious in certain sections. Other insect pests 
attack citrus trees to a greater or less extent, but those just mentioned 
are generally the most injurious, and the principal method of their 
control is fumigation with hydrocyanic-acid gas. 
i See Bui. 79, Bur. Ent., U. S. Dept. Agr., 1908, p. 10. 
67330°— Bull. 90—12 2 
