## 4 Biological Control and the Three Ps: Predation, Parasitism, and Pathogens
### Predation  
In Mediterranean olive cultivars, the main potential groups that predate pest species are Formicidae, Araneae, Forficulidae, Staphilinidae, Carabidae, and Scolopendromorpha [88; 89; 90; 91]. Among the measures proposed in the management guides for the _olf_, the edaphic predatory arthropods community could contribute to the reduction in the population levels of the olive fly during the autumn and winter months [89]. As stated above (Figure 2), the larvae of the late generations in the autumn pupae in the soil, where they spend the winter buried and where they are more vulnerable to being predated; therefore, the number of adults that reach the reproductive period in spring decreases significantly [16]. The roles of carabids and their relative abundances in Spanish groves were tested in functional response experiments, revealing that the species _Perostichus globosus_ is a better candidate than _Orthomus barburus_--the most abundant carabid species in the southeast region of Madrid--for the biological control of _olf_[71]. _P. globosus_ was also suggested as a more efficient predator than _Calathus granatensis_ in Portuguese cultures [88]. In both cases, the adult size of the carabid species was relevant in the predation rates. In the same line, predation by coleoptera upon _B. oleae_ was also assessed in carabids and staphilinids picked up in olive groves from Tuscany (Italy) [92; 93]. Many studies have also been performed analysing the role of spiders in IPM given that they are an abundant and generalist group in olive agroecosystems that would contribute to the regulation of _olf_ populations [94; 95; 96; 97]. However, its abundance can generally be affected by soil regimens (reduced in intensive cultures), landscape effects, or prey abundance, among others [79]. Notwithstanding, the real effect of predation on the damage reduction by the _olf_ is still unknown. Thus, it becomes absolutely necessary to perform the study of the trophic webs and analyse the arthropods community according to their relative abundances and feeding preferences in the context of pest control [80; 88; 98]. In this line, _post mortem_ studies analysing the presence of preys in the predator's gut would provide a clearer profile of the trophic web, confirming the real role of each group in the biological control of each pest. For instance, carabids, ants, spiders, and earwigs have already been confirmed as _B. oleae_ predators in molecular gut contain assays using individuals that were picked up during the fall and spring in olive cultures in Madrid [99; 100]. As previously said, several arthropod groups can predate the different olive pest species. Chrysopidae, or green lacewings (Neuroptera), have been recognized as one of the most effective biological control agents of many orchard pests, including the olive moth [101]. Indeed, lacewings are currently cultivated for sale and release in different crops. Among others, _Chrysoperla carnea_, whose larvae are oophagous, plays an important role in the regulation of _P. oleae_ populations [102]. Other Neuroptera species reported to predate on _P. oleae_ eggs are _Mallada flavifrons, Mallada picteti, Mallada prasina, Nineta vittata_, and _Rexa lordina_[103]. In contrast to the voracious larvae, adults just feed upon vegetal substances such as pollen or nectar. This fact highlights, again, the importance of the surrounding landscape and surrounding vegetation to promote IPM [35; 38; 104]. Ants also have beneficial effects in biological control because they consume large numbers of pest insects [105]. For instance, _Tapinoma_ complex, one of the most abundant groups in the olive agroecosystem, is a strong candidate for olive moth control in Spanish olive groves [106]. Indeed, although IPM is certainly important to maintain ant communities and promote their roles as pest control agents, the _Tapinoma_ species seems to be little affected by the landscape heterogeneity [91]. Other species referenced as predators are _Camponotus_ sp., _Formica subrufa_, or _Crematogaster scutellaris_[107].