Impact of woody semi-natural habitats on the abundance and diversity of green lacewings in olive orchards

Abstract

Habitat management is a conservation biological control technique which helps to reduce the use of inputs in olive orchards and also to improve sustainability. Recent studies of olive orchards have pointed out that vegetation cover, which provides food resources, as well as reproduction and refuge sites, increases Chrysopidae populations and diversity. However, little is known about the effect of woody semi-natural habitats (SNHs) in olive orchards. In this context, our study aims to determine the attraction of adult Chrysopidae to different tree species in SNHs adjacent to olive orchards in order to promote the conservation biological control of this key predator. We vacuumed 75 almond, oak, olive and pine trees fortnightly between April and October of 2016. The trees were chosen at random and evenly distributed among five organic olive orchards selected according to their availability. Oak trees recorded the highest abundance, species richness and diversity levels of adult Chrysopidae, while olive trees had the highest abundance of Chrysopidae larvae. A total of 20 green lacewing species, belonging to seven different genera, were collected, of which Chrysoperla mutata (McLachlan, 1898), Chrysoperla pallida Henry et al., 2002 and Pseudomallada (prasinus) pp3 (Duelli and Henry, 2020) were the most abundant during the period of the study and had a preference for olive trees (C. mutata and C. pallida) and oak trees P. (prasinus) pp3. Furthermore, the number of Chrysopidae larvae collected showed a positive correlation with the percentage of predated eggs in the anthophagous and carpophagous generations of Prays oleae.