Davis, J.J. 1924 Estimating the abundance and damage by the San José scale.. Journal of Economic Entomology 17: 192-195.

Notes: The gradual increase of the San José scale, Aspidiotus perniciosus, is less likely to be recognized before it becomes a serious factor than many insects which appear suddenly or which cause immediately visible injury, nor is the relative importance of the loss of trees in comparison with an annual crop usually realized. The various types and degrees of injury must be taken into consideration in estimating abundance and damage, which may include a weakening or killing of the tree, spotting of fruit so as to make it unmarketable, and subjection of the trees to further insect and disease troubles following the weakening effect of scale. Other factors entering into the problem are the vigor and resistance of individual trees and individual varieties to scale injury. The degree of infestation and method of making counts are reported. To reach a basis for estimating monetary losses figures are given which enable the author to estimate the crop loss to an acre of apples, if allowed to become badly infested, to be $1,008.00 and this even if the scale is eventually controlled and the trees brought back into a thrifty condition.