Natürliche Vermehrung der Schildlaus (Quadraspidiosus perniciosus), ihre künstliche Massenzucht auf Melonen, daran ablaufende Massenzucht des Parasiten. Freilassung der Parasiten zur erfolgreichen Einbürgerung und Ausbreitung: Imagines unter einem Zelt und Aufhängen von Melonen mit parasitierten Schildläusen in befallenen Baumkronen.

The film shows the biological control of the introduced San-José-scale, an important orchard pest, by importation, mass production and release of an specific parasitic hymenopteron: Prospaltella perniciosi. After some typical damage in the field the following subjects are shown in detail: The natural reproduction of the scale, its artifical mass breeding on melons, the rearing of the parasite based on this host production, details of the parasite's life-history, and two types of release: as adults under a tent, and by suspending of a melon covered with parasitized scales infested orchard trees. Both ways have obtained establishment and spread of the parasite.