Habitat Diversity Increases Chrysoperla carnea s.l. (Stephens, 1836) (Neuroptera, Chrysopidae) Abundance in Olive Landscapes

Abstract

Chrysoperla carnea s.l., a vital predator in olive groves, plays a key role in reducing the reliance on pesticides. Despite its efficacy, habitat diversification at the landscape level can compromise its effectiveness as a generalist natural enemy, diverting its attention from olive pests to other resources. To unravel its habitat preferences and maximize biocontrol services, a comprehensive study was conducted, collecting specimens monthly across diverse habitats in a Portuguese olive grove landscape. These habitats included shrublands, “montado,” grasslands, eucalyptus and pine forests, vineyards, and olive groves. The findings revealed C. carnea s.l. displayed a widespread presence in all habitats, with peak abundance initially observed in olive groves, coinciding with the presence of its preferred prey, Prays oleae. However, the peak abundance of this species varies among habitats, with the highest numbers initially observed in olive groves, gradually decreasing throughout the summer and reaching the lowest levels in vineyards. Significantly, habitat diversification at the landscape level contributes to an increased abundance of C. carnea s.l. in olive groves. This suggests that diversifying available resources aids in sustaining natural enemy populations in proximity to the targeted crop, thereby enhancing their efficacy in pest control. Consequently, we advocate for stakeholders in olive cultivation to promote landscape-scale habitat diversity by preserving, restoring, or fostering alternative habitats surrounding olive groves.