The Influence of Mixed Green Covers, a New Trend in Organic Olive Growing, on the Efficiency of Predatory Insects

Abstract

Intensive soil tillage and the resulting erosion constitutes one of the main problems in olive growing. Palliative practices such as implementing vegetable covers are encouraged. Recently, the method of adding inert green roofs to the soil, either alone or in combination with adventitious vegetation, has stood out. Assessing this agronomic measure is our main objective. This research was conducted in 2022 in the Jaén province (southern Spain), wherein olive groves with different managements were selected: (i) conventional, free from vegetation, (ii) ecologically managed olive grove containing a cover of adventitious vegetation (VC), and (iii) ecologically managed olive grove in which the remains of pruning are added to the adventitious cover (VC-MIX). Vegetation inventories and beneficial insect monitoring were performed using a combined device with chromatic and olfactory trapping. The olive moth (Prays oleae) and lacewing predators were selected as the indicator species. Both the beneficial insect diversity and relative plant abundance were higher in the VC-MIX, where the highest rates of predation by lacewings were found (88%). In turn, these parameters in the VC olive surpassed those of the conventional olive grove. The factors involved in the notable differences between the three management types are discussed.