LOUISIANA CIRCULAR No. 4. 



History of the San Jose Scale. 



The San Jt>se scale was first described in 1880, by Prof. J. H. 

 Comstock, then Entomologist of the U. S. Dept. of Agriculture, 

 from specimens taken in Santa Clara County, California. Prof. 

 Comstock at that time gave it the very appropriate name of As- 

 pidiotus perniciosus, meaning the pernicious scale, as it has since 

 proved itself to be one of the most pernicious pests with which 

 the fruit grower has ever had to deal. 



Owing to its abundance in the San Jose Valley of California 

 the common name of "San Jose scale" came to be applied to it. 

 Although not described until 1880, the insect 

 had, as early as 1873, become a serious pest 

 in the San Jose Valley.* How it obtained a 

 foothold in California, and the country from 

 which it had been imported, remained for 

 many years in doubt. The finding, in later 

 years, of San Jose scale -upon trees imported 

 from Japan, gave rise to the opinion that that 

 country was its native home. Not until 

 1901-02 was the original home of the insect 

 known with certainty. During those years 

 Prof. C. L. Marlatt of the U. S. Dept. of 

 Agriculture, made a special trip of investiga- 

 tion through Japan and China, with the result 

 that he definitely located the native home of 

 the San Jose scale in that portion of China 

 lying to the north and west of Pekin.** While the San Jose scale 

 continued to encroach upon new territory in California, it was ap- 

 parently several years before it entered the country east of the 

 Rocky Mountains. The first discovery of the pest in the East 

 was at Charlottesville, Va., in 1893, and subsequent investiga- 

 tions showed beyond a reasonable doubt that it had reached Char- 

 lottesville from a nursery in New Jersey. The discovery of in- 

 festations in various parts of the country, all of them traceable 

 d'rectly or indirectly to one or the other of two New Jersey nui 

 series, started an investigation which revealed the fact that the 



FIG. 2. Sau Jose 

 scale on peach twig, 

 twice natural size 

 (After Britton, Bui. 

 151, Conn. Exp. 

 Station). 



*Rnl No 3 n ser.. Division of Entomology, p. 12. 

 "Yearbook,' U.' I. Dept. of Agriculture, 11102, p. ito 



