Neuffer, G. 1990 Zur Abundanz und Gradation der San-José-Schildlaus Quadraspidiotus perniciosus Comst. und deren Gegenspieler Prospaltella perniciosi Tow. Eine Zusammenfassung 30 jahriger Untersuchungen.. Gesunde Pflanzen 42: 89-96.

Notes: Title in English: [The abundance and increase of the San Jose scale Quadraspidiotus perniciosus Comst. and its natural enemy Prospaltella perniciosi Tow. A summary of 30 years' investigations.] The orchard pest Quadraspidiotus perniciosus was first recorded in the German Federal Republic in 1946, and the parasitoid Prospaltella perniciosi [Encarsia perniciosi] was first introduced and released as a biological control agent against the scale in 1950. The spread and increase of the pest and its natural enemy since are described. The parasitoid became naturalized and has spread and has reduced infestation from up to 100% in 1960 to 4.2% in 1989.