Storing up Treasures: Storage Potential of Macrolophus pygmaeus (Hemiptera: Heteroptera: Miridae) Nymphs for Application in Biological Control

Abstract

Long-term storage is an important component of insect mass-rearing systems, prolonging the shelf life of biocontrol agents during a low-demand period or a temporary lack of suitable food. Macrolophus pygmaeus is a predatory heteropteran, mass-reared and widely used for the biological control of arthropod pests in greenhouses. With the aim to determine the optimal conditions and acceptable duration of cold storage, we evaluated the impact of different periods of storage of fed and starved third instar nymphs of M. pygmaeus at different temperatures on nymphal survival, adult emergence, and female fecundity. Four storage temperatures (3, 6, 9, and 12 °C) were tested. The longevity of starved nymphs decreased with an increase in the storage temperature, with a maximum of about 40 days at 3 °C, whereas the longest lifetime of nymphs fed on eggs of the grain moth Sitotroga cerealella (about 150 days) was observed at 9 °C. Further experiments demonstrated that the third instar nymphs of M. pygmaeus fed with eggs of the grain moth can be stored at 9 °C for 30 days, with a moderate (10–20%) decrease in survival and fecundity, whereas the survival of starved nymphs decreased by half after 10 days of storage at 3 °C.