Critical nymphal stages of Orius laevigatus for suboptimal feeding with pollen: Regulated deficit feeding

Abstract

Augmentative biological control has proven to be highly effective in numerous greenhouse crops, largely due to the use of omnivorous predators. Orius laevigatus (Fieber) is a key natural enemy against thrips, and for practical application, this predator is mass-reared in biofactories, where the optimal artificial diet consists of Ephestia kuehniella eggs, a costly resource. However, Orius is known to complete its development on pollen, although the quality of the individuals produced is generally lower. This led us to question whether there are less critical developmental stages which feeding could be reduced without negatively impacting performance, naming it as “regulated deficit feeding”. To test this, we examined how partially substituting Ephestia eggs with pollen at specific developmental stages would affect insect development and rearing cost. Additionally, we investigated whether supplementing suboptimal amounts of Ephestia eggs with pollen throughout the entire nymphal period could improve overall development. Moreover, we carried out this study comparing two standard commercial populations of O. laevigatus with two genetically improved strains for better performance feeding on pollen. Two periods were established for nymphal development: from N1 to N3 and from N4 to N5. The period from N1 to N3 was the most critical for suboptimal feeding, leading to reduced survival, body size and female fecundity. Feeding with Ephestia eggs in this critical period (N1-N3) but with pollen in the less critical (N4-N5) reduced the cost of rearing to 30–70% of that of the optimal diet, without impacting biological parameters except body size, especially in the artificially selected populations.