2 BULLETIN 1040, U. S. DEPARTMENT OF AGRICULTUEE. 



considered it a new species and gave it the name P. citrophilus. 

 During the first four years various measures of control were tried 

 by the growers and county and State officials without any marked 

 success; in fact, the infested area continued to increase rapidly and 

 the infestations became more severe. 



The importance of this pest to the citrus industry and inability to 

 control it led, in the summer of 1917, to a request for the United 

 States Department of Agriculture to take up the problem, and the 

 investigation was immediately started. Effective control methods 

 were worked out in 1917 and 1918 and were generally employed 

 throughout the infested area during 1919. 



SAN BERNARDINO 



RIVERSIDE 



SAN DIEGO 



Fig. 1. — Present known distribution of the citrophilus mealybug {Pseudococcus gahani) 



in Southern California. 



HISTORY AND DISTRIBUTION. 



Definite records of the introduction of this mealybug into South- 

 ern California are lacking, but a study of its earliest occurrence and 

 spread would indicate that it was brought in on some ornamental 

 plants imported into Upland during 1910. The infestation of about 

 3 acres at the time of the first records (1913) had spread by the fall 

 of 1915 to twice that area. By 1917 approximately 600 acres were 

 infested, but since that time its spread has been greatly retarded by 

 control means, though a few small infestations outside of the control 

 area have been noted (fig. 1). 



Shortly after the discovery of the Upland infestation the pest was 

 found in Pasadena and has now become distributed over a consider- 



