DeBach, P. 1947a Cottony cusion scale, vedalia and DDT in central California.. California Citrograph 32: 406-407.

Notes: Icerya purchasi was accidentally introduced into California from Australia in the 1860's. Vedalia, a predatory beetle and Cryptochaetum, a parasitic fly were successfully introduced for control. In the early 1940's the use of DDT was initiated which resulted in the loss of biological control agents and renewed outbreaks of I. purchasi.