10 HYDROCYANIC-ACID GAS FUMIGATION IN CALIFORNIA. 



THE YELLOW SCALE. 



(Chrysomphalus citrinus Coq.) 



Infestations of the yellow scale appear to be most marked in the 

 foothills region of the San Gabriel Valley and along the Sierra Madre 

 Range through Upland and Cucamonga. It causes considerable dam- 

 age at Redlands, San Bernardino County, yet elsewhere is not 

 regarded as a very serious pest. Tins insect infests the leaves and 

 fruit, seldom occurring on the branches. The young are born alive, 

 as in the case of the red scale, to which it is closely related. 



THE MEALY BUG. 



(Pseudococcus citri Risso.) 



The mealy bug occurs in various sections of the southern part of 

 California. The districts of greatest injury are in southern San Diego 

 County and at Santa Paula, in Ventura County. Little effort for its 

 control has been made except in these two places. Tins insect at- 

 tacks fruit, leaves, and branches, secreting a honeydew, which is fol- 

 lowed by a black fungus, as in the case of the black scale. Its injury 

 is much greater than that of the black scale because it discolors and 

 weakens the rind of the fruit at those places where it extracts the 

 juice. The cottony secretion in which the eggs are deposited is 

 difficult to remove. The severe washing which this fruit requires, 

 combined with its weakened rind in certain places, produces a heavy 

 decay in such fruits as are treated in tins manner. The mealy bug 

 occurs on several hosts beside citrus trees. The young are hatched 

 from eggs deposited by the adult. 



APPARATUS. 

 TENTS. 



When hydrocyanic-acid gas was first employed in treating orchards 

 the apparatus used in the process was of a very cumbersome nature. 1 

 The most popular apparatus consisted of tents more or less of a bell- 

 shaped nature manipulated by a high derrick mounted on a wagon. 

 The wagon was drawn between the rows and the tents lowered over 

 or raised from the trees by means of ropes attached to the derricks. 

 The use of such apparatus was difficult, slow, and costly. 



SHEET TENTS. 



During 1892 Mr. C. W. Finch, a fumigator at Riverside, CaL, 

 devised a much simpler and cheaper apparatus than those theretofore 

 used, which consisted of flat sheet tents, octagonal in outline. (Fig. 7, 

 p. 29.) This simplified tent was rapidly adopted, and now sheet 



1 Report of Entomologist, I'. S. Dept. Agr., 1S87, p. 126. 



