Mathys, G., & Guignard, E. 1965 Étude de l'efficacité de Prospaltella perniciosi Tow. en Suisse parasite du pou de San-José. [Study of the effectiveness of Prospaltella perniciosi Tow. in Switzerland, a parasite of the San José scale.]. Entomophaga 10(93): 193-220.

Notes: Six different strains of Prospaltella perniciosi have been tested since 1957 with regard to their efficacy as parasites of the San José scale Quadraspidiotus perniciosus under the conditions of western and southern Switzerland. A Russian, a Chinese and a North American strain from Illinois gave the best results both in laboratory rearing and when applied in experimental orchards. The results were promising enough to justify tests on a larger scale in which P. perniciosi is being released systematically on greater surfaces. The parasite can, apparently, survive even when the host population is small.