FUMIGATION OF CITRUS TREES. 



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 Coccidse, a group of insects popularly 





SAN BERNARDINO 



ORIV£RSID£ 

 V/tRUNGTVN 



RIVERSIDE. 



O£SCO/V0/OO 



SAN DIEGO 



OLAK£S/D£ 

 0£L CAJON 

 SAN 0/E60 

 OCHULA VISTA 



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 (LepidosapJies beclcii Newm.), the red scale (CJirysom- 

 phalus aurantii Mask.), and the black scale (Saissetia olese Bern.). 

 The yellow scale (ChrysompJialus 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 



