OBSERVATIONS AND EXPERIMENTS ON 

 THE SAN JOSE SCALE 



By STEPHEN A. FORBES, State Entomologist 



The product of a considerable amount of field and laboratory- 

 work on the San Jose scale, much of which was done or begun under 

 the immediate supervision of Jas. A. West, of my office staff, has 

 lain for some time in the form of field notes and unfinished manu- 

 script prepared by Mr. West before his lamented death in 1909. Lapse 

 of time and the studies of others have made some of this material obso- 

 lete; but such part of it as is here presented seems still useful and 

 worthy of publication. The larger part of this paper relates, indeed, to 

 a series of experiments not yet finished in 1909, but continued for two 

 years thereafter, and reported now from the original field notes made 

 partly by Mr. West, but mainly by W. P. Flint and L. M. Smith, 

 who were his aids also in the earlier work. 



The San Jose Scale on Fruits 



The San Jose scale infests not only the trunk, limbs, and leaves, 

 but also the fruit of trees, often so marking the fruit as to make it 

 unfit for sale. The danger of dissemination by this means is, how- 

 ever, very slight, since the fruit itself or the parings from it arc 

 little likely to be so placed that young insects from them can secure 

 a lodgment or a suitable breeding-place. Our attention was especially 

 called to this subject by a statement made in a bulletin of the Divi- 

 sion of Zoology of the Pennsylvania State Department of Agriculture 

 (Vol. IV, No. 7, November, 1906) which says, referring to the San 

 Jose scale: "Its abundance upon fruit of any kind need not be con- 

 sidered alarming, as it can not possibly spread from fruit that has 

 begun to ripen, because it dies on such fruits and can not reproduce 

 from them. In Bulletin No. 8 of the same series, the same writer 

 says: "This pest dies upon the fruit as soon as it ripens, and con- 

 sequently there is no danger of disseminating or spreading it by this 

 means." 



October 3, 1906, Mr. West obtained three ripe Jonathan apples 

 infested by the San Jose scale and kept them under observation on 

 his office table. The scale multiplied readily on all of them. One 

 of the apples was kept until November 29, at which time there were 

 more than thrice as many well-developed San Jose scales on it as in 

 the beginning, and most of them were alive. There were also many 



