Circular No. 124. Issued August 12, 1910. 



United States Department of Agriculture, 



BUREAU OF ENTOMOLOGY. 

 L. O. HOWARD, Entomologist and Chief of Bureau. 



THE SAN JOSE SCALE AND ITS CONTROL." 



By A. L. QUAINTANCE, 



In Charge of Deciduous Fruit Insect Investigations. 

 CHARACTER OF INJURY. 



The San Jose or Chine.se scale (Aspidiotus perniciosus Comstock) 

 infests practically all portions of its host plants that are above 

 ground — the trunk, limbs, and branches — and when abundant it may 

 occur on the leaves and fruit. Injury results from the extraction, by 

 the scale insects, of the juices of the i)lant. At first this mereh^ 

 checks growth, but as the insects increase in number the speedy kill- 

 ing of the branches and twigs follows, resulting finally in the death 

 of the i)lants. In addition to the extraction, by the scales, of sap as 

 food, tlie puncturing of the bark by the slender sucking mouth-parts, 

 results in a diseased and often pitted condition; the inner bark, or 

 cambium, showing a reddish discoloration, as exposed in cutting 

 with a knife, and the bark itself may crack, in stone fruits exuding 

 drops or masses of gum. A reddening effect is also much in evi- 

 dence as red rings around the scales on the bark, especially of the 

 apple and pear, and on the fruits of these plants, though not charac- 

 teristic of any one scale species. 



On ])eac]i tlie scales have a tendency to infest to a greater extent 

 the older liml)s and branches than the newer growth, as the wood 

 1 3-ear old. On apple and pear, the terminal twigs are quite gen- 

 erally infestetl, and many of the young may find their way to the 

 fruit, settling principally in the calyx and stem cavities. Most 

 varieties of fruit trees and plants infested from the nurserv, in 

 the absence of treatment, perhaps never reach fruiting condition. 



a An extended recent account of this insect will bo found in Bulletin 62 of this 

 Bureau, "The San Jose or Chinese Scale," by (\ T>. Marlatt, which may be obtained 

 of the Superintendent of Documents, Governmenl Printing Office, Wa.-^hinglon, D. C, 

 for 25 cents. Foreign applicants should .«end 4 cents additional to cover postage. 

 [Civ. 1-24] 



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