Faunistic Study of Auchenorrhyncha in Olive Orchards in Greece, Including First Records of Species

Abstract

The study of Auchenorrhyncha species composition in Greek olive orchards is crucial due to the potential threat of Xylella fastidiosa invading the region. Recent studies have begun exploring agricultural landscapes, particularly olive and citrus orchards. From 2016 to 2022, biodiversity surveys were conducted in thirteen olive orchards across three regions of Greece: Peloponnese, Sterea Ellada, and the Northeast Aegean. Malaise traps were installed in each orchard and monitored monthly, supplemented by sweep net sampling in two orchards to capture less mobile species and assess their association with host plants. A total of 14,771 specimens were collected, representing 125 species predominantly feeding on weeds. The dominant species were the Typhlocybinae Hebata decipiens and Zyginidia pullula, while Euscelis lineolata was the most common Deltocephalinae. Aphrophoridae, including Philaenus spumarius and Neophilaenus campestris, were more effectively collected with sweep nets, primarily from Avena sterilis L. This study offers a detailed overview of the Auchenorrhyncha fauna in Greek olive orchards, providing essential insights for developing strategies to prevent the invasion of Xylella fastidiosa.

1. Introduction

Xylella fastidiosa Wells et al. is a Gram-negative bacterial plant pathogen that causes a variety of economically devastating diseases in numerous crops, including Pierce’s disease (PD) of grapes, citrus variegated chlorosis (CVC), phony peach disease, and olive quick decline syndrome (OQDS). This bacterium is of significant concern due to its extensive genetic and phenotypic diversity, which has led to its classification into four subspecies: X. fastidiosa fastidiosa, X. fastidiosa pauca, X. fastidiosa multiplex, and X. fastidiosa sandyi. In North America, subspecies like X. fastidiosa multiplex and X. fastidiosa fastidiosa affect almond, peach, oak, and grapevine, while X. fastidiosa pauca has caused significant damage in South America, particularly in coffee, citrus, and olive crops [1,2,3].

In recent years, X. fastidiosa has been increasingly detected across Europe, threatening a wide range of crops. The first major outbreak occurred in southern Italy, where X. fastidiosa pauca was detected in olive orchards in the Apulia region, causing olive quick decline syndrome [4,5]. This outbreak affected over 10,000 hectares of olive trees, leading to severe economic and agricultural impacts. Since then, the pathogen has been detected in several other European countries.

In France, X. fastidiosa was first identified in Corsica in 2015 on ornamental plants like Polygala myrtifolia L. and later spread to mainland France, affecting regions such as Provence-Alpes-Côte d’Azur [6]. The subspecies X. fastidiosa multiplex was responsible for these infections. In Spain, X. fastidiosa was detected in the Balearic Islands in 2016, where both X. fastidiosa fastidiosa and X. fastidiosa multiplex were reported, with infections extending to almond trees, sweet cherries, and other ornamental plants [7,8]. In mainland Spain, outbreaks occurred in Alicante, infecting almond trees, and in other areas of Valencia, further escalating concerns about the pathogen’s spread in the Iberian Peninsula [9]. Additionally, in 2019, X. fastidiosa was detected in Portugal, affecting olive trees in the Vila Nova de Gaia region [10]. This detection marked another critical spread of the pathogen in Mediterranean Europe, which has a high density of host plants susceptible to X. fastidiosa.

The rapid spread of X. fastidiosa across Europe has led to significant quarantine measures and concerted efforts to monitor and control its vectors. The pathogen’s ability to infect a wide variety of plant species, combined with the similarities in climatic conditions across much of the Mediterranean region, raises concerns that other countries, such as Greece, may soon face similar outbreaks. Given Greece’s extensive olive cultivation, with approximately 900,000 hectares of olive trees representing a significant portion of the agricultural landscape [11], the introduction of X. fastidiosa would have severe consequences for the country’s economy and agriculture.

X. fastidiosa is primarily transmitted by xylem-feeding Auchenorrhyncha (Hemiptera), including species from the families Cicadellidae (leafhoppers and sharpshooters), Aphrophoridae (spittlebugs), and Cercopidae (froghoppers). These insects acquire the bacterium when they feed on the xylem of infected plants and can subsequently transmit it to healthy plants, facilitating the spread of the disease [12,13,14,15]. According to Purcell [16], every xylem fluid-feeding hemipteran should be considered a potential vector of the bacterium, highlighting the need for comprehensive faunistic studies to identify and manage these vectors.

In Europe, two primary xylem-feeding species have been identified as the main vectors of X. fastidiosa: Philaenus spumarius (L.) and Neophilaenus campestris (Fallén), both of which have been found to carry the pathogen in olive orchards in southern Italy [17]. However, recent studies have expanded the scope of potential vectors. For example, Elbeaino et al. [18] discovered that Euscelis lineolata (Brullé), a phloem-feeding leafhopper, was infected with X. fastidiosa, suggesting that specialized phloem feeders could also become infected by probing xylem vessels. Similarly, Chuche et al. [19] demonstrated that Scaphoideus titanus Ball, another phloem feeder, can reach xylem tissues and feed on them for extended periods, further complicating the understanding of vector dynamics.

Given the expanding knowledge of X. fastidiosa vectors and the potential for new species to act as transmitters of the bacterium, it is crucial to investigate the entire Auchenorrhyncha fauna present in regions at risk of pathogen introduction, not only to identify current vectors but also to assess the potential for other species to become vectors under certain conditions. In Italy, while considerable data on Auchenorrhyncha fauna exists [20,21,22], the lack of specific studies in olive orchards before the arrival of X. fastidiosa delayed the implementation of effective vector management strategies. However, following the pathogen’s introduction, a series of studies quickly prioritized the monitoring of Auchenorrhyncha populations in olive orchards [17,18,23].

Although recent studies have begun to explore the Auchenorrhyncha fauna in Greek olive orchards [24,25], there is still a significant knowledge gap, particularly regarding the role of these insects as potential vectors of X. fastidiosa. These studies have provided valuable insights into the species composition, diversity, and seasonal abundance of Auchenorrhyncha under different management systems. However, more extensive research is required to fully understand the seasonal dynamics, regional variation, and the potential role of these insects in the transmission of X. fastidiosa in Greece. Developing effective monitoring and control strategies is crucial to mitigate the risk of X. fastidiosa becoming established in this key olive-producing region. This study aims to build on previous research by providing a comprehensive survey of Auchenorrhyncha species in Greek olive orchards, with a focus on documenting the full spectrum of Auchenorrhyncha fauna rather than solely potential vector species. The research was conducted across three of the country’s most important olive-growing regions: Central (Sterea Ellada), Southern (Peloponnese), and Northern Greece (Northern Aegean, Lesvos Island). In addition to documenting the seasonal appearance and abundance of Auchenorrhyncha species, this study contributes new data on the regional distribution and composition of these insects in different agroecological zones collected by sweep net sampling of specific ground vegetation cover. By examining both xylem and phloem feeders, this research provides crucial insights into the Auchenorrhyncha fauna associated with olive cultivation in Greece, expanding the knowledge necessary for effective pest and vector management strategies in areas at risk for X. fastidiosa introduction.

2. Materials and Methods

2.1. Sampling Areas

This study was conducted in 13 olive orchards in Greece, between 2016 and 2022. The orchards were distributed across three geographical regions of Greece: Peloponnese (Achaia, Argolida, Ileia, Messinia), Sterea Ellada (Attica and the island of Euboea), and Lesvos Island (North Aegean) (Figure 1). The orchards included a range of management systems: some complied with organic standards according to European Union (EU) legislation (Council Regulation (EC) 834/2007), others adhered to the EU Common Agricultural Policy (CAP) framework for conventional farming, and a few received no treatments. The surrounding vegetation mainly consisted of other orchards, including olives and citrus, with occasional vineyards. Differences in climatic conditions between regions—ranging from Mediterranean coastal climates to more temperate inland conditions—could influence insect population dynamics and are relevant for interpreting the results.

2.1.1. Sterea Ellada

Athens (Ath), Agricultural University of Athens campus (Attica): (37°98′18.57″ N, 23°70′68.59″ E). Olive tree varieties: more than 30 varieties, including Greek, Spanish, Italian, and other European varieties. Surrounding orchards: olive yards, citrus, stone fruits, apples, pears, etc. Also, there are pistachio trees, a vineyard, and a botanical garden with many ornamental trees. Weed control was performed using a mechanical tiller attached to a tractor. No pesticides were applied. Sampling period: 2016–2019 (with Malaise trap), 2020–2021 (with sweep net).

Istiea–North Euboea conventional (Ist1), Euboea Island: (38°57′47.7″ N, 23°09′03.0″ E). Olive tree varieties: Kalamon and Amfissis. Surrounding orchards: olive yards. Herbicides were used for weed control. Sampling period: 2018–2019 (with Malaise trap).

Istiea–North Euboea organic (Ist2), Euboea Island: (38°58′06.8″ N, 23°07′36.3″ E). Olive tree variety: Kalamon. Surrounding orchards: olive yards. Weed control was achieved using a mechanical tiller attached to a tractor. Sampling period: 2018–2019 (with Malaise trap).

Istiea–North Euboea–no treatment (Ist3), Euboea Island: (38°57′46.7″ N, 23°08′37.7″ E). Olive tree variety: Amfissis. Surrounding orchards: olive yards. The wild vegetation remained intact. Sampling period: 2018–2019 (with Malaise trap).

2.1.2. Northeast Aegean

Lakerda (Lak), Lesvos Island: (39°04′46.1″ N, 26°31′57.5″ E). Olive tree variety: Kolovi (Valanolia). Surrounding orchards: olive yards. This organic orchard used a lawnmower for weed control. Sampling period: 2018–2022 (with Malaise trap).

Kalloni (Kal), Lesvos Island: (39°14′08.2″ N, 26°13′01.8″ E). Olive tree variety: Kolovi (Valanolia). Surrounding orchards: olive yards and nearby river and the saltpans of Kalloni gulf. Conventional orchard, with herbicides and mechanical tiller attached to a tractor used for weed control. Sampling period: 2018–2020 (with Malaise trap).

Nifida (Nif), Lesvos Island: (39°08′66.5″ N, 26°13′33.2″ E). Olive tree variety: Kolovi (Valanolia). Surrounding orchards: olive yards, seaside region. Conventional orchard, with herbicides and mechanical tiller attached to a tractor used for weed control. Sampling period: 2018–2020 (with Malaise trap).

Pamfila (Pam), Lesvos Island: (39°09′10.3″ N, 26°31′40.8″ E). Olive tree variety: Kolovi (Valanolia). Surrounding orchards: olive yards. Conventional orchard, with herbicides and mechanical tiller attached to a tractor used for weed control. Sampling period: 2017–2018 (with Malaise trap).

2.1.3. Peloponnese

Koutsopodi–Argolida (Kts): (37°67′36.9″ N, 22°68′97.2″ E). Olive tree variety: Koroneiki. Surrounding orchards: olive yards and some citrus trees. Organic orchard, with mechanical tiller attached to a tractor used for weed control. Sampling period: 2018–2019 (with Malaise trap).

Pelekanada–Messinia (Pel): (37°05′09.28″ N, 21°83′68.94″ E). Olive tree varieties: Mavrolia Messinias and Koroneiki. Surrounding orchards: olive yards, vineyards, and wild shrubs and trees, such as Erica manipuliflora Salisb., Pistacia spp., Vitex agnus-castus L., Sarcopoterium spinosum (L.) Spach., Quercus spp., Pyrus spp. Conventional orchard, with herbicides used for weed control. Sampling period: 2016–2017 (with Malaise trap).

Kiparissia–Messinia (Kip): (37°15′35.94″ N, 21°40′42.85″ E). Olive trees variety: Koroneiki. Surrounding orchards: olive yards and some citrus trees. Conventional orchard, use of mechanical tiller attached to a tractor for weed control. Sampling period: 2019–2020 (with Malaise trap).

Fragka–Achaia (Fra): (38°04′20.5″ N, 21°29′08.1″ E). Olive tree variety: Koroneiki. Surrounding orchards: olive yards. A mechanical tiller attached to a tractor was used for weed control and no pesticides were applied. Sampling period 2019–2020 (with Malaise trap).

Pirgos–Ileia (Pir): (37°42′39.4″ N, 21°27′33.5″ E). Olive tree variety: Kalamon and Koroneiki. Surrounding orchards: olive yards, some citrus trees, and almonds. Conventional orchard. Mechanical tiller attached to a tractor was used for weed control. Sampling period 2021–2022 (with sweep net).

In each orchard, a white-colored custom-made Malaise trap was installed at the center to study the presence, seasonal appearance, and abundance of Auchenorrhyncha species. Each trap measured 170 cm in height at the top end and 110 cm at the lower end, with a length of 160 cm and a width of 180 cm, providing a total interception area of 165 × 110 cm². A 600-mL plastic container was attached in each trap with 98% ethanol as a preservation fluid. Samples were collected monthly and were then sent to the Laboratory of Zoology and Entomology of the Agricultural University of Athens for species identification. Samplings from each orchard lasted for at least one year, with some orchards (Athens and Lakerda) sampled for 3 consecutive years.

Additionally, sweep net samplings were conducted in two orchards, Pirgos’ and Athens’, for one year each to target key vector species like aphrophorids, which are less likely to be captured by Malaise traps. These samplings were conducted from dominant weeds (recorded number of Auchenorrhyncha species per weed species), woody hosts and from the canopy of olives with a custom-made entomological sweeping net (39 cm diameter). Every fortnight, 10 consecutive sweeps were undertaken from the dominant plants in the field in 5 different areas in the orchard with that plant species.

2.2. Classification

The taxonomic classification of the collected Auchenorrhyncha species followed the taxonomic keys of Ribaut [26,27], Ossiannilsson [28,29,30], Guglielmino and Bückle [31], and Dmitriev [32]. A very useful supporting tool was the Auchenorrhyncha collection of the late Prof. Dr. Sakis Drosopoulos, housed at the laboratory of Agricultural Zoology and Entomology. Male genitalia were dissected, kept in KOH (10%) (Merck KGaA, Darmstadt, Germany) for 2 h (30 min. for Typhlocybinae), mounted on microscope slides in glycerol, and observed under stereoscopic and microscopic microscope. Females were identified in genus level, and, subsequently, if all the specimens of a genus in a specific sampling belonged to one species, the female specimens were added to that species. The nomenclature that followed was according to Dmitriev [32], the website TaxonPages.

2.3. Data Analysis

Insect dominance for each orchard was determined using the classification system proposed by Curry [33], Cusack et al. [34], and Emmanuel [35]. Species were categorized as ‘dominant’ (>10% of the total individuals), ‘influent’ (5–10%), or ‘recedent’ (<5%).

Diversity was estimated by Simpson’s Diversity Index (1-D) [36], where 0 represents low diversity and 1 represents infinite diversity. The value of D was calculated using the following formula:

$$D=\sum _{i=1}^s{\displaystyle \frac{n_i(n_i-1)}{N(N-1)}}$$

n_i = the number of individuals of a particular auchenorrhynchan species; N = the total number of individuals of all auchenorrhynchan species.

Simpson’s Diversity Index represents the probability that two individuals randomly selected from a sample belong to different species. This index is particularly useful for assessing the evenness (E) and richness (S) of species within each orchard ecosystem. Richness (S) is the total number of species in every orchard, and evenness or equitability (E) can be calculated by taking Simpson’s Reciprocal Index (1/D) and expressing it as a proportion of S. Equitability takes a value between 0 to 1, with 1 being complete evenness (i.e., where there are exactly equal numbers of individuals per species). The formula used was

$$E={\displaystyle \frac{1}{D}}\times {\displaystyle \frac{1}{S}}$$

3. Results

3.1. Species Composition

In total, 14,771 Auchenorrhyncha belonging to 109 species were collected using a Malaise trap (

Table 1. Percentage of every species collected in each orchard with Malaise trap (+ indicates the species collected in less than 5%. − indicates absence from that orchard) (Ath = Athens, Lak = Lakerda, Lesvos, Kal = Kalloni, Lesvos, Nif = Nifida, Lesvos Pam = Pamfila, Lesvos, Ist1 = Istiea conventional, Euboea, Ist2 = organic, Euboea, Ist3 = abandoned, Euboea, Kts = Koutsopodi, Peloponnese, Pel = Pelekanada, Peloponnese, Kip = Kiparissia, Peloponnese, Fra = Fragka, Peloponnese).

Species	Ath (%)	Lak (%)	Kal (%)	Nif (%)	Pam (%)	Ist1 (%)	Ist2 (%)	Ist3 (%)	Kts (%)	Pel (%)	Kip (%)	Fra (%)
Total Number	2566	314	1442	311	320	2761	1090	2652	1231	366	1533	185
Aphrophoridae, Aphrophorinae
Lepyronia coleoptrata (L.)	−	−	−	−	−	+	−	+	−	−	−	−
Philaenus spumarius (L.)	+	+	+	+	+	+	+	+	+	+	+	+
Neophilaenus (Neophilaenulus) campestris (Fallén)	−	5.79	+	+	+	+	+	+	−	−	−	+
Neophilaenus (Neophilaenus) lineatus (L.)	−	−	−	−	−	+	−	−	−	−	−	−
Cercopidae, Cercopinae
Cercopis sanguinolenta (Scopoli)	−	−	−	−	−	+	+	+	+	−	−	−
Cicadellidae, Aphrodinae
Anoscopus albifrons (L.)	−	+	−	−	−	−	−	+	+	−	−	−
Aphrodes bicincta (Schrank)	−	−	−	−	−	−	+	+	−	+	−	−
Cicadellidae, Deltocephalinae
Allygus modestus (Scott)	+	−	−	−	−	+	+	+	+	8.71	−	−
Anaconura acuticeps (Ribaut)	−	−	−	−	−	−	+	−	−	−	−	−
Anoplotettix putoni (Ribaut)	+	−	−	−	−	−	−	−	+	8.43	+	−
Anoplotettix fuscovenosus (Ferrari)	−	+	−	−	−	+	+	+	−	−	−	−
Arocephalus (Arocephalus) longiceps (Kirschbaum)	+	−	−	−	−	−	−	−	−	−	−	−
Balclutha frontalis (Ferrari)	+	+	+	+	−	8.84	10.46	+	−	−	5.94	+
Balclutha punctata (Fabricius)	10.02	−	−	−	−	−	−	−	−	−	5.68	+
Balclutha saltuella (Kirschbaum)	+	−	+	−	−	+	+	+	−	−	−	+
Cicadula (Cicadula) lineatopunctata (Matsumura)	−	−	−	−	−	+	+	+	−	−	−	−
Cicadulina bipunctata (Melichar)	+	+	8.20	−	−	17.17	+	+	−	−	6.52	−
Docotettix cornutus (Ribaut)	−	+	+	+	−	−	−	−	−	−	−	−
Eohardya fraudulenta (Horváth)	+	−	+	−	−	−	−	+	−	−	−	−
Epistagma (Epistagma) guttulinervis (Kirschbaum)	−	−	−	−	−	−	−	−	−	−	+	+
Eupelix cuspidata (Fabricius)	−	−	−	−	−	−	−	+	−	−	−	−
Euscelidius mundus (Haupt)	−	+	+	−	−	−	−	−	−	−	−	−
Euscelidius variegatus (Kirschbaum)	+	−	−	−	−	−	−	−	−	−	−	+
Euscelis alsia (Ribaut)	+	+	+	5.47	−	+	+	−	−	−	−	+
Euscelis lineolata (Brullé)	+	7.40	9.92	+	+	+	14.50	+	−	12.64	+	+
Exitianus capicola (Stål)	+	+	+	+	−	+	+	+	+	+	+	+
Fieberiella florii (Stål)	−	−	−	−	−	−	−	+	−	−	−	−
Fieberiella septentrionalis (Wagner)	−	−	−	−	−	−	−	−	+	+	−	−
Goniagnathus (Goniozygotes) bolivari (Melichar)	−	−	−	+	−	−	−	−	−	−	−	+
Goniagnathus (Goniagnathus) brevis (Herrich-Schäffer)	−	+	+	+	−	−	−	−	−	−	−	−
Grypotellus staurus (Ivanoff)	+	−	−	−	−	−	+	+	−	−	−	−
Hecalus glaucescens (Fieber)	−	−	−	−	−	+	+	−	−	−	−	−
Jassargus (Obtujargus) obtusivalvis (Kirschbaum)	−	−	−	−	−	−	+	−	−	−	−	−
Macrosteles quadripunctulatus (Kirschbaum)	−	−	+	−	+		−	−	−	−	+	−
Macrosteles ramosus (Ribaut)	−	−	+	−	−	−	−	−	−	−	−	−
Macrosteles sexnotatus (Fallén)	−	−	+	−	−	−	−	−	−	−	−	−
Maiestas schmidtgeni (Wagner)	+	+	+	+	+	+	+	+	+	+	+	−
Melillaia desbrochersi (Lethierry)	−	+	−	−	−	−	−	−	−	−	−	−
Mocydia crocea (Herrich-Schäffer)	−	−	−	−	−	−	−	−	−	+	−	−
Neoaliturus (Circulifer) haematoceps (Mulsant & Rey)	+	+	+	−	−	+	−	−	+	−	−	−
Neoaliturus (Neoaliturus) fenestratus (Herrich-Schäffer)	−	−	+	−	−	+	+	+	+	−	−	−
Nesoclutha erythrocephala (Ferrari)	−	−	−	−	−	+	−	−	−	−	−	−
Opsius stactogalus (Fieber)	−	−	−	+	−	−	−	−	−	−	−	−
Orosius orientalis (Matsumura)	+	−	+	−	−	−	−	−	−	−	−	−
Paralimnus (Paralimnus) zachvatkini (Emeljanov)	−	−	−	−	−	+	+	−	−	−	−	−
Paramesodes lucaniae (Dlabola)	−	−	−	−	−	+	−	−	−	−	−	−
Phlepsius intricatus (Herrich-Schäffer)	+	−	+	+	−	+	+	+	+	+	−	+
Phlogotettix cyclops (Herrich-Schäffer)	−	−	−	−	−	−	−	+	−	−	−	−
Proceps acicularis (Mulsant & Rey)	−	+	−	−	−	−	−	−	−	−	−	−
Psammotettix alienus (Dahlbom)	5.56	+	12.54	+	−	+	+	+	−	+	+	+
Psammotettix confinis (Dahlbom)	−	−	+	−	−	−	−	−	−	−	−	−
Psammotettix notatus (Melichar)	+	−	−	−	+	−	−	−	+	+	−	−
Selenocephalus pallidus (Kirschbaum)	−	+	+	6.11	−	−	+	−	−	−	−	−
Streptanus (Streptanulus) albanicus (Horváth)	−	+	−	−	−	−	−	−	−	+	−	−
Synophropsis lauri (Horváth)	+	−	+	−	−	+	+	+	−	+	−	+
Thamnotettix zelleri (Kirschbaum)	+	25.08	+	49.19	+	+	15.41	−	+	+	+	−
Varta rubrostriata (Horváth)	−	−	−	−	−	+	+	+	−	−	−	−
Cicadellidae, Eurymelinae
Acericerus vittifrons (Kirschbaum)	+	−	−	−	−	−	−	−	−	−	−	−
Sulamicerus stali (Fieber)	+	−	−	−	−	−	−	−	−	−	−	−
Cicadellidae, Iassinae
Batracomorphus (Batracomorphus) irroratus (Lewis)	−	−	−	−	−	+	−	+	−	−	−	−
Cicadellidae, Megopthalminae
Agallia consobrina (Curtis)	+	−	−	−	−	+	+	+	+	+	−	−
Anaceratagallia (Anaceratagallia) glabra (Dmitriev)	−	+	+	+	−	+	+	+	+	+	+	+
Anaceratagallia (Anaceratagallia) ribauti (Ossiannilsson)	−	−	+	+	+	−	+	+	−	−	+	−
Austroagallia sinuata (Mulsant & Rey)	−	+	+	+	−	+	−	−	−	−	−	−
Megopthalmus scabripennis (Edwards)	+	+	+	+	−	+	+	+	+	−	−	−
Cicadellidae, Typhlocybinae
Anzygina honiloa (Kirkaldy)	+	+	−	−	−	−	−	−	−	−	−	−
Arboridia parvula (Boheman)	−	−	−	−	−	−	−	−	−	+	−	−
Arboridia (Arboridia) versuta (Melichar)	−	−	−	−	−	−	−	−	−	+	−	−
Assymetrasca decedens (Paoli)	+		+	+		+	+	+	−	−	+	−
Edwardsiana platanicola (Vidano)	−	−	−	−	−	−	−	+	−	−	−	−
Eupteryx (Eupteryx) collina (Flor)	−	−	−	−	−	−	−	−	−	7.02	−	−
Eupteryx (Eupteryx) curtisii (Flor)	−	−	−	−	−	−	−	+	−	−	−	−
Eupteryx (Eupteryx) decemnotata (Rey)	+	−	−	−	−	−	−	−	−	−	−	−
Eupteryx (Eupteryx) filicum (Newman)	+	−	−	−	−	−	−	−	−	−	−	−
Eupteryx (Eupteryx) gyaurdagica (Dlabola)	−	14.47	+	+	−	−	−	−	−	−	−	−
Eupteryx (Eupteryx) insulana (Ribaut)	−	−	+	−	−	+	+	+	−	−	−	−
Eupteryx (Eupteryx) melissae (Curtis)	+	−	−	−	+	+	+	+	+	−	−	−
Eupteryx (Eupteryx) rostrata (Ribaut)	−	−	−	−	−	−	−	−	−	+	−	−
Eupteryx (Eupteryx) urticae (Fabricius)	+	−	−	−	−	−	−	−	−	−	−	−
Eupteryx (Eupteryx) zelleri (Kirschbaum)	−	−	−	−	−	+	+	39.52	−	−	7.44	−
Ficocyba ficaria (Horváth)	+	−	−	−	−	+	−	+	−	−	−	−
Frutioidia (Frutioidia) bisignata (Mulsant & Rey)	−	−	−	−	−	−	−	+	−	−	−	−
Hauptidia (Hauptidia) provincialis (Ribaut)	+	+	+	−	−	+	+	+	+	9.83	20.74	−
Hebata (Alboneurasca) decipiens (Paoli)	+	−	14.96	+	32.19	12.57	5.69	+	6.91	+	27.46	6.49
Hebata (Signatasca) vitis (Göthe)	+	−	−	−	−	−	−	−	−	−	+	+
Liguropia juniperi (Lethierry)	+	−	−	−	−	−	−	−	−	−	−	−
Lindbergina cretica (Asche)	−	+	−	−	−	−	−	−	−	−	−	−
Ribautiana cruciata (Ribaut)	−	−	+	+	−	−	+	−	−	−	−	−
Ribautiana tenerrima (Herrich-Schäffer)	−	−	−	−	−	+	+	18.89	−	−	−	−
Zygina (Hypericiella) hyperici (Herrich-Schäffer)	−	−	−	−	−	−	−	−	+	−	−	−
Zygina (Zygina) angusta (Lethierry)	+	−	−	−	−	−	−	−	−	−	−	−
Zygina (Zygina) nivea (Mulsant & Rey)	+	−	−	−	−	−	−	−	−	−	−	−
Zygina (Zygina) rhamni (Ferrari)	−	−	−	−	−	+	+	+	−	−	−	−
Zygina (Zygina) roseipennis (Tollin)	−	−	−	+	−	−	−	−	−	−	−	−
Zygina (Zygina) suavis (Rey)	−	−	−	−	−	−	−	−	+	+	−	−
Zygina (Zygina) tiliae (Fallén)	−	−	−	−	−	−	−	−	−	+	−	−
Zyginella pulchra (Löw)	+	−	−	−	−	+	−	−	−	−	+	−
Zyginidia adamczewskii (Dworakowska)	+	−	−	+	−	−	−	−	−	−	−	−
Zyginidia pullula (Boheman)	16.62	+	10.06	+	40.00	36.22	18.53	+	72.38	10.11	+	−
Wagneriala sinuata (Then)	−	−	−	−	−	−	−	+	−	−	−	−
Delphacidae, Stenocraninae
Stenocranus fuscovittatus (Stål)	−	−	−	−	−	+	−	+	−	−	−	−
Delphacidae, Delphacinae
Laodelphax striatellus (Fallén)	−	−	+	−	−	+	−	+	−	−	−	−
Toya (Metadelphax) propinqua (Fieber)	−	+	+	−	−	+	+	+	+	+	−	−
Dictyopharidae, Dityopharinae
Dictyophara (Dictyophara) europaea (L.)	−	−	−	−	+	−	+	+	−	−	−	−
Flatidae, Flatinae
Metcalfa pruinosa (Say)	−	−	−	−	−	−	+	+	−	−	−	−
Phantia subquadrata (Herrich-Schäffer)	−	+	+	+	−	−	+	+	−	−	−	−
Issidae, Hysteropterinae
Agalmatium bilobum (Fieber)	−	−	−	−	−	+	+	+	−	−	−	−
Agalmatium flavescens (Olivier)	−	+	−	−	−	−	−	−	−	+	−	−
Latilica antalyica (Dlabola)	+	+	−	−	−	−	−	−	−	−	−	−
Latilica maculipes (Melichar)	5.73	−	−	−	−	−	−	−	−	−	+	−

). Of these, 385 individuals belonged to the suborder Fulgoromorpha, while the remaining 14,386 belonged to Cicadomorpha. The collected species were classified into seven families: Cicadellidae (95 species), Aphrophoridae (4 species), Issidae (4 species), Delphacidae (2 species), Flatidae (2 species), Dictyopharidae (1 species), and Cercopidae (1 species). Across all regions, Cicadellidae was the most abundant and diverse family, represented mainly by Typhlocybinae (35 species), which also accounted for 52.05% of the total population collected with Malaise traps. The second most abundant but the most diverse subfamily was Deltocephalinae (50 species), consisting of 40.42% of the total population. Fewer species were found in the subfamilies Aphrodinae (two species), Eurymelinae (two species), Iassinae (one species), and Megopthalminae (five species), which contributed smaller percentages to the total population.

The dominance ranking of species was calculated for each orchard individually. The results showed that two Typhlocybinae species were dominant in most orchards: Zyginidia pullula (with a population ranging from 10.06% to 72.38% of the total population) and Hebata decipiens (ranging from 12.57% to 32.19% of the total population). Both species were present even in small numbers in most of the orchards. Other common Typhlocybinae included Assymetrasca decedens and species of the genus Eupteryx, where they were recorded in every olive grove, with Eupteryx zelleri being dominant in the untreated Istiea’s grove (Euboea Island) with a relative abundance of 39.52%, while Eupteryx gyardagica was dominant in Lakerda’s grove (Lesvos Island) at 14.47%. Moreover, Hauptidia provincialis was present in most orchards and was influent in some, reaching 20.74% of the total population in Kiparissia’s orchard (Messinia).

Moreover, several Deltocephalinae species were either dominant or influent in the orchards. Balclutha spp. and Euscelis spp. were recorded in every orchard. Balclutha frontalis was dominant in Istiea’s organic orchard (10.46%), while Balclutha punctata was influent in the Athens’s orchard (10.02%). Euscelis lineolata was dominant in both the Pelekanada orchard (Messinia) (12.64%) and the organic Istiea orchard (14.5%) and was also influent in Kalloni (Lesvos Island) (9.92%). Cicadulina bipunctata was dominant in Istiea’s conventional orchard (17.17%) and influent in Kalloni (8.20%). Other widespread species, present in almost all orchards, included Synophropsis lauri, Phlepsius intricate, Thamnotettix zelleri (with relative abundances of 15.41% in organic Istiea orchard, 49.19% in Nifida, and 25.08% in Lakerda on Lesvos Island), Maiestas schmidtgeni, and Exitianus capicola, and several species of the genus Psammotettix, with Psammotettix alienus being the most common representative (12.54% in Kalloni’s orchard on Lesvos Island).

Megopthalminae were represented by a small number of species in each orchard, with Anaceratagallia glabra (formerly known as Anaceratagallia laevis) being the most common.

Aphrophorids were collected in small numbers using Malaise traps, with Philaenus spumarius present in almost every orchard. Neophilaenus campestris was found in low numbers in a few orchards. Other species from the family Aphrophoridae, such as Lepyronia coleoptrata, Neophilaenus lineatus, and Cercopis sanguinolenta, were collected sporadically.

Fulgoromorpha were generally found more sporadically. The delphacid species Toya (Metadelphax) propinqua was the most common and was found in most orchards. The family Issidae was represented in relatively high numbers in some orchards, such as in Athens, with Latilica maculipes accounting for 5.73% of the total population.

3.2. Seasonal Fluctuations

The seasonal fluctuation for the Auchenorrhyncha population was calculated for the Athens’s orchard and Lakerda’s orchard on Lesvos Island, where data were available for three consecutive years. The population showed clear peaks in the warmer months in both locations.

In the Athens orchard, population growth began in late April each year, with the peak occurring during the summer months. The peaks of the population were n = 306 in August 2016, n = 714 in June 2017, n = 189, and in July 2018 (Figure 2). In the Lakerda orchard, the population increase started earlier, at the beginning of April, with the peak occurring in May, showing population sizes of n = 42 in May 2018, n = 67 in May 2020, and n = 26 in May 2021 (Figure 3). In both regions, the lowest numbers were recorded during the winter, when temperatures are lower and adult Auchenorrhyncha are less mobile.

The Simpson diversity index was calculated for each orchard (

Table 2. Species richness, Simpson’s Diversity and Evenness Indices for each locality.

Management System	Locality	Richness (S)	Simpson’s Index of Diversity (1-D)	Evenness (E)
Organic	Athens	62	0.932	0.240
Organic	Lakerda	52	0.901	0.194
Conventional	Kalloni	64	0.924	0.203
Conventional	Nifida	43	0.746	0.092
Conventional	Pamfila	17	0.735	0.222
Conventional	Istiea	48	0.824	0.118
Organic	Istiea	45	0.899	0.220
No-treatments	Istiea	57	0.815	0.095
Organic	Koutsopodi	55	0.468	0.034
Conventional	Pelekanada	47	0.928	0.296
Conventional	Kiparissia	35	0.858	0.201
Organic	Fragka	44	0.881	0.191
Conventional	Pirgos (sweep net)	32	0.897	0.303
Organic	Athens (sweep net)	18	0.637	0.153

), with the highest values observed in the organic orchards of Athens, Kalloni, and Lakerda, ranging from 0.901 to 0.932. Interestingly, high diversity was also found in the conventional orchard at Pelekanada, where we had the greatest evenness in comparison with other populations collected with a Malaise trap. In contrast, the lowest diversity and evenness were recorded in the organic orchard of Koutsopodi.

3.3. Sweep Net Results

Sweep net sampling was performed in Pirgos and Athens orchards. A total of 1533 Auchenorrhyncha were collected, belonging to 43 species. Six families were recorded: Aphrophoridae (2 species), Cicadellidae (32 species), Delphacidae (4 species), Flatidae (1 species), Dictyopharidae (1 species), and Issidae (3 species). Most of these species were collected from plants of the family Poaceae, as shown in

Table 3. Percentage of Auchenorrhyncha species collected with sweep net from Pirgos (Peloponnese) and Athens (Attica) (Pir = Pirgos, Ath = Athens). + indicates percentage less than 5%, − indicates absence in that field.

Species	Pir (%)	Pirgos’ Plant Species	Ath (%)	Athens’ Plant Species
Philaenus spumarius (L.)	14.10	AS	15.85	PL, OE, AS, HM, CD, ASV, PA, SE, MS
Neophilaenus (Neophilaenulus) campestris (Fallén)	16.98	AS	+	PA, SE, AS
Aphrodes bicincta (Schrank)	−	−	+	HM, SO
Allygidius (Dicrallygus) mayri (Kirschbaum)	+	PO	−	−
Allygus modestus (Scott)	−	−	+	OE, PL, MS
Anaconura acuticeps (Ribaut)	−	−	+	CD
Anoplotettix putoni (Ribaut)	+	PO	+	OE, HM, ASV
Balclutha frontalis (Ferrari)	14.24	AC	−	−
Balclutha punctata (Fabricius)	+	AC	+	OE, ASV
Balclutha saltuella (Kirschbaum)	+	AC	−	−
Cicadulina bipunctata (Melichar)	+	PO	−	−
Doratura stylata (Boheman)	+	AC, CD	−	−
Epistagma (Epistagma) guttulinervis (Kirschbaum)	+	CD	−	−
Euscelidius variegatus (Kirschbaum)	−	−	+	AS, HM, PHA
Euscelis lineolata (Brullé)	+	AS, CD	−	−
Euscelis ohausi (Wagner)	+	PO	−	−
Exitianus capicola (Stål)	6.19	CD	+	CD, AS
Exitianus nanus (Distant)	+	PO	−	−
Hecalus storai (Lindberg)	+	CD	−	−
Maiestas schmidtgeni (Wagner)	+	CD	−	−
Mocydiopsis longicauda (Remane)	+	PO	−	−
Mocydiopsis monticola (Remane)	+	PO	−	−
Nesoclutha erythrocephala (Ferrari)	+	AS, HM, CD, ASV, PA	−	−
Phlepsius intricatus (Herrich-Schäffer)	+	PO	−	−
Psammotettix alienus (Dahlbom)	14.96	AS, HM, CD, ASV, PA	+	CD
Streptanus (Streptanulus) albanicus (Horváth)	−	−	+	AS, HM
Synophropsis lauri (Horváth)	−	−	8.17	OE, ASV
Thamnotettix zelleri (Kirschbaum)	+	PO	+	OE, AS, MS, SA, HM, ASV
Anaceratagallia (Anaceratagallia) glabra (Dmitriev)	+	AS	−	−
Anaceratagallia (Anaceratagallia) ribauti (Ossiannilsson)	−	−	+	SO
Sulamicerus stali (Fieber)	−	−	57.20	PL
Hauptidia (Hauptidia) provincialis (Ribaut)	+	MA, TR	−	−
Hebata (Alboneurasca) decipiens (Paoli)	+	MA, TR	−	−
Zyginidia pullula (Boheman)	+	MA, TR	−	−
Asiraca clavicornis (Fabricius)	+	PO	−	−
Euidopsis truncata (Ribaut)	+	PO	−	−
Eurysella brunnea (Melichar)	+	PO	−	−
Toya (Metadelphax) propinqua (Fieber)	+	AC, CD	+	CD
Dictyophara (Dictyophara) europaea (Linnaeus)	−	−	+	AV
Phantia subquadrata (Herrich-Schäffer)	+	PO	−	−
Clybeccus declivum (Dlabola)	+	AS	−	−
Latilica antalyica (Dlabola)	−	−	+	OE, ASV
Latilica maculipes (Melichar)	+	AS	−	−

Ν^α: number of individuals captured. Plant species and abbreviations: Amaranthus viridis L. = AV; Apera spica-venti (L.) P. Beauv. = ASV; Agrostis capillaris L. = AC; Avena sterilis L. = AS; Cynodon dactylon (L.) Pers. = CD; Hordeum murinum L. = HM; Malva silvestris L. = MS; Malva sp. = MA; Olea europaea L. = OE; Phalaris arundinacea L. = PHA; Pistacia lentiscus L. = PL; Poa annua L. = PA; Poaceae mix = PO; Sinapis alba L. = SA; Solanum elaeagnifolium Cav. = SE; Sonchus oleraceus L. = SO; Trifolium sp. = TR.

. Seven species were collected from the canopy of olives: P. spumarius during spring and autumn, Al. modestus, A. putoni, B. punctata, S. lauri, T. zelleri, and the issid Latilica antalyica.

The dominance ranking from the sweep net sampling was quite different from that of the Malaise trap. In the Pirgos orchard, the most collected species with a sweep net was Neophilaenus campestris (16.98%), followed by two deltocephalins, Psammotettix alienus (14.96%), and Balclutha frontalis (14.25%). Philaenus spumarius (14.10%) was the fourth most collected species. In the Athens orchard, P. spumarius was the most collected species with a sweep net (15.85%), while Su. stali was collected in significant numbers (57.2%) but only above lentisk shrubs present in the field.

Two population peaks were recorded in the Athens orchard during autumn (early October to early December) and during spring (mid-May to August) (Figure 4a). Similar results were recorded in the Pirgos orchard, with two peaks a little earlier (early September to late November and late March to early July) (Figure 4b). The spittlebug population showed two peaks throughout the year. The first peak occurred in spring, with adults collected from mid-April to early June, and a population peak occurred at the end of April in both orchards. The second peak occurred in autumn, with adults collected from late October to late December, peaking in early November in the Athens orchard, and late September to early December in the Pirgos orchard (Figure 4a,b).

Most adult spittlebugs were collected above Poaceae weeds. In Pirgos, all the spittlebug specimens of both P. spumarius and N. campestris were found exclusively on Avena sterilis (Figure 4b), while in Athens they were collected from various hosts (Figure 5a,b): P. spumarius primarily was collected above A. sterilis from mid-October to late December of 2020 and early October to late December of 2021 peaking in both years in early November. Another important host in spring was Hordeum murinum where most adults were collected in April of 2021 and significant numbers were collected on Apera apica-venti in November of 2020 and April of 2021 (Figure 5a). Philaenus spumarius was also collected from the olive canopy in both spring and autumn, albeit in small numbers. Additionally, 1–2 adults were collected from Solanum elaeagnifolium, Malva silvestris, and Pistacia lentiscus, but these were not included in the diagram due to their low numbers. N. campestris was collected in November and December of 2021 from Poa annua and from A. sterilis during winter in both years, and one adult was collected also from So. elaeagnifolium (Figure 5b).

4. Discussion

The species composition of Auchenorrhyncha in olive orchards in Greece is heavily influenced by geographical locality, neighboring plant species, and the weeds present within the orchards. The most common and abundant species observed during this study were primarily oligophagous or polyphagous, inhabiting dry meadows and shrubs. The most dominant species, Zyginidia pullula, feeds primarily on grasses of the family Poaceae [37,38,39], which are typical ground vegetation in Greek orchards. Other prevalent Typhlocybinae species such as Hebata decipiens, Eupteryx spp., and Hauptidia provincialis are also herbivorous, feeding on ground vegetation and herbaceous plants [31,40].

Similarly, the dominant Deltocephalinae species observed were grass-feeding Auchenorrhyncha. Balclutha frontalis and Balclutha punctata, both feeding on grasses, especially those of the family Poaceae [38,41], were very common, with B. frontalis found in 10 out of 13 orchards. These species were collected in large numbers from Agrostis capillaris using a sweep net.

Euscelis lineolata, a species preferring both Poaceae and Fabaceae, was another common Auchenorrhyncha species in olive and citrus orchards in previous studies undertaken in Greece [24,42,43], and also in orchards in Italy and France [44,45]. In this study, it was found in all orchards in large numbers, characterized as dominant or frequent in most of them. With a sweep net, it was collected above Avena sterillis and Cynodon dactylon, both grasses of the family Poaceae.

Other widespread frequently observed Deltocephalinae species included Psammotettix alienus, Exitianus capicola, Allygus modestus, Cicadulina bipunctata, Maiestas schmidtgeni, Phlespsius intricatus and Thamnotettix zelleri. Maiestas schmidtgeni, Ph. intricatus, Psammotettix spp., Al. modestus, and T. zelleri are polyphagous and commonly found contributing to the biodiversity in vineyard and olive agroecosystems [46,47,48], while Τ. zelleri also feeds on woody plants [22,38]. Synophropsis lauri, which was collected in 8 out of 13 fields and in high numbers above the canopy of olives, as in previous studies in Greece [42], feeds on woody plants, including olives [21,22,49]. Some species, such as S. lauri, T. zelleri, Ph. intricatus, and Anoplotettix putoni, were likely underrepresented in the Malaise trap collections due to their canopy-dwelling habits, whereas the Typhlocybinae species were collected in high numbers like Z. pullula, Eupteryx spp., Hebata spp., and Hauptidia sp. since they are more mobile and inhabit ground vegetation.

Most of the species found in the olive orchards are common and widespread throughout Greece, with their presence largely dependent on the composition of the undergrowth vegetation. The specific location and the neighboring plant species, whether they are other cultivated fields or rural gardens, play a crucial role in shaping the composition of Auchenorrhyncha species in the orchard. As a result, many species may occur in olive orchards incidentally. For instance, Zyginella pulchra and Sulamicerus stali, are species that feed on Pistacia spp. Zyginella pulchra is polyphagous, feeding on trees of the family Sapindaceae, while Su. stali is monophagous, exclusively feeding on Pistacia spp. [37,40,50]. Both species were found in the Athens orchard, with Su. stali being particularly abundant during spring, as it was also collected using a sweep net. Their presence can be attributed to the neighboring pistachio field and the scattered lentisk shrubs, which were heavily infested with Su. stali. A similar situation was observed with two species found in the Athens orchard: Liguropia juniperi and Acericerus vittifrons, which feed on cypress and acer trees, respectively [40,49,50]. These species were likely present due to the proximity of the botanical garden adjacent to the olive orchard. In Nifida’s orchard, which is located in a seaside region, the species Opsius stactogalus was recorded. This species feeds monophagously on Tamarix spp. [40], and was likely present due to the nearby Tamarix trees along the coastline near the road. It is possible that a larger population of O. stactogalus was feeding on these trees and subsequently moved into the neighboring olive orchard. Macrosteles spp. generally prefer moist, wet habitats, with their nymphs feeding on sedges (Carex), woodrushes (Luzula), rushes (Juncus), and grasses (Poaceae) [38]. Both Macrosteles ramosus and Macrosteles sexnotatus were found in Kalloni’s orchard, which is located near saltpans and a large wetland. The third species collected, Macrosteles quadripunctulatus, is the only species in the genus that also inhibits dry regions and it was the only one found in other orchards [40]. Although the majority of species collected during this study were not directly associated with olive trees, non-crop hosts such as weeds, neighboring cultivations, and even gardens can contribute to the pest pressure. This is because Auchenorrhyncha species are highly mobile and capable of dispersing and alternating between hosts [51].

Differences in the auchenorrhynchan fauna between olive orchards also exist due to different localities since some species are native to a specific region or have restricted distribution in Greece. Docotettix cornutus, the olive leafhopper, is a species distributed in Cyprus, Turkey, and Greece, mainly in the islands of the northeast Aegean [52]. Here, it was collected only from the olive orchards of Lesvos. In Turkey, this species was collected in the canopy of olives in high numbers, so it could have a larger population in olives of Lesvos, occurring in the canopy of the trees and could be a potential pest [53].

During this study, new distribution data were obtained for several species. Clybeccus declivum was found in abundance in the Pirgos orchard in the Peloponnese, collected with a sweep net from Avena sterilis L. This is the first record of the species in the Peloponnese, as it was previously reported only on Rhodes island in the Dodecanese [54]. Eupteryx zelleri was previously known only from the Rodopi, Olympus, and Pindos mountains in northern and northwestern Greece, according to the collection of Sakis Drosopoulos. However, our study revealed that this species also occurs in Sterea Ellada and Peloponnese, significantly broadening its known range. Similarly, Balclutha frontalis was previously recorded in Sterea Ellada and Crete Island, but we now confirm its presence in the Peloponnese and Lesvos Island as well. The Australian-native species Anzygina honiloa, first recorded in Greece in 2018 in Athens, [55], was also recorded in Lesvos Island during this study. This suggests that the species has spread to other localities in Greece within just a few years, indicating a rapid expansion of its distribution.

Moreover, two new records for Greece were made during this study: Hecalus storai and Exitianus nanus, both collected using a sweep net in the Pirgos olive orchard (Figure 6 and Figure 7). H. storai is distributed in France and Bulgaria [32], and in this study, it was collected from Cynodon dactylon in the olive orchard. On the other hand, E. nanus has a broader distribution across Asia, Africa, Australia, and southwest America. In Europe, it has been recorded only in Italy [32].

4.1. Potential Vectors

In this study, the most common spittlebug collected was Philaenus spumarius, found in almost every field, albeit in low numbers, using Malaise traps. The second most common species was Neophilaenus campestris, which was found in 7 out of 13 fields. Higher numbers of both species were collected using a sweep net in comparison with Malaise, highlighting the efficiency of sweep nets in capturing aphrophorids. Also, according to Dongiovanni et al. [56], yellow sticky traps are more efficient, even from a sweep net, for monitoring spittlebugs from the olive canopy, especially during summer, while the combination with a sweep net helps to accurately estimate the spittlebug population by finding the right period for insecticide application. This suggests that these species may exist in higher numbers in other fields where only Malaise traps were used. In Athens, where we used both trapping methods, we can clearly see the huge difference in collecting spittlebugs. With a sweep net, both spittlebugs were collected, and P. spumarius was dominant, while with a Malaise trap, only P. spumarius was collected, at 0.61% of the total population. The most collected species with a Malaise trap was Z. pullulan, with a percentage of 16.62%, while it was not collected with a sweep net. Previous studies in Greece [25,42] embrace these results, with P. spumarius and N. campestris effectively collected using a sweep net from both the canopy of olives and surrounding weeds across the country. Weeds from the Poaceae family, particularly Avena sterilis, appear to support a significant proportion of the adult population of spittlebugs, probably serving as a preferred host for both P. spumarius and N. campestris. Thompson et al. [57] assert that records of nymph feeding provide the most reliable evidence on species’ host plants. We cannot, therefore, be sure that adult spittlebugs were feeding on the plants from which they were swept. They may simply have been resting on these plants or associated with other plants within the vegetation. Nonetheless, nymphs of P. spumarius have been recorded feeding on A. sterilis in the Mediterranean, suggesting that it may also be a valid host for adults [57,58].

The spittlebug fauna observed in this study is similar to that of other Mediterranean European countries, such as Spain and Italy, where the bacterium X. fastidiosa has been established [17,23,59]. However, unlike the studies of Ben Moussa et al. [17] and Cornara et al. [23], our results align more closely with those of Tsagkarakis et al. [24], Antonatos et al. [42], and Theodorou et al. [25], where Philaenus spumarius was captured during both spring and autumn in higher numbers. This pattern suggests that this species may be bivoltine, or as Antonatos et al. [42] proposed, it may migrate away from the olive orchards during summer and return in autumn after the first rains. The observations of Drosopoulos and Asche [60] also support the idea of P. spumarius being bivoltine or partly bivoltine at elevations below 1000 m, where the majority of olive orchards are located. This bivoltine cycle could make olive orchards more vulnerable to the transmission of X. fastidiosa if the bacterium were to enter Greece.

Other spittlebug species collected during the survey were found sporadically in low numbers. These species are included in the EFSA [61] list of potential vectors for Europe, although they were not as prominent in this study.

4.2. Biodiversity Indices

When examining species diversity, it appears that the surrounding environment plays a more significant role than the cultivation system itself. The highest biodiversity indices were recorded in the conventional orchards of Kalloni and Pelekanada and the organic orchards of Athens. In Kalloni, the orchard is located next to the saltpans of Kalloni, which is considered a hotspot of biodiversity, providing a moist environment that supports a rich variety of common wild plants. The Athens orchard is located near a botanical garden, a vineyard, and an area with a variety of fruit trees. Similarly, in Pelekanada, the presence of numerous forest trees and shrubs contributed to the higher biodiversity. There, the greatest evenness was observed, even though the number of species collected was lower than the other two (S_Pel = 47 < S_kal = 64, S_ath = 62). In contrast, the lowest biodiversity index and evenness were recorded in the organic orchard of Koutsopodi, which resembled a monoculture of olives. The field, covering 2.5 acres, was surrounded by more olive trees, limiting the diversity of other plant species and likely reducing overall insect biodiversity. The species Z. pullula consisted of 72.37% of the total population, which decreased the biodiversity dramatically. In the Istiea region, where both organic and conventional cultivation systems were present, a clear difference in biodiversity was observed. The organic orchard exhibited higher biodiversity and greater evenness than its conventional counterpart, suggesting that while the surrounding environment is the primary driver of species diversity, the cultivation system still plays a secondary role in shaping Auchenorrhyncha populations [25].

4.3. Seasonal Fluctuations

The population peaks of Auchenorrhyncha were observed in the spring and summer months, particularly in samples collected with Malaise traps. This could be attributed to the fact that many species alternate hosts during these seasons, and most adults have emerged from the nymphal stage. The higher temperatures during spring and summer likely increase insect activity, while during rainy days, Auchenorrhyncha species are less active and more likely to hide, reducing their presence in the traps. Additionally, the emergence of many wild plant species during spring and summer provides a more diverse food and habitat source for Auchenorrhyncha, further contributing to the increased species diversity during these months.

On the other hand, sweep net catches were higher during autumn. The cooler temperatures during this period may slow down the insects’ metabolic rate, reducing their rapid ‘jump’ reaction and making them easier to catch [62]. Moreover, the wide variety of wild plants available in the fields during autumn likely supports a higher Auchenorrhyncha population, despite the lower overall temperature.

5. Conclusions

This study focused on the Auchenorrhyncha fauna in olive orchards across three geographical divisions in Greece: Sterea Ellada, Peloponnese, and Lesvos Island. The results demonstrate that species composition is influenced by the ground vegetation, the surrounding environment, geographical locality, and the trapping method employed. Most of the species collected were weed feeding, emphasizing the importance of weeds as a food source, alternative host, and site for oviposition. P. spumarius, B. frontalis, C. bipunctata, E. alsia, E. lineolata, Ex. capicola, M. schmidtgeni, Ph. intricatus, Ps. alienus, S. lauri, T. zelleri, Ha. provincialis, H. decipiens, Z. pullula, An. Glabra, and the delphacid T. propinqua were ubiquitous, even occurring in small numbers. Malaise traps proved more efficient in capturing smaller, more active species, like Typhlocybinae, which predominantly inhabit ground vegetation. The dominant species of orchards of Lesvos Island were T. zelleri for the Lakerda and Nufida orchards, H. decipiens and Z. pullula for the Kalloni and Pamfila orchards, P. alienus for the Kalloni orchard, and Eu. gyardagica for the Lakerda orchard. All orchards of Sterea Ellada (Euboea and Athens) had Z. pullula as the dominant species. Eu. zelleri was dominant in the Istiea orchard with no treatments; B. frontalis, T. zelleri, and E. lineolatus in the Istiea organic field; H. decipiens and C. bipunctata in the Istiea conventional field; and Al. modestus and A. putoni in the Athens field. For Peloponnese, H. decipiens were dominant in the Fragka, Koutsopodi and Kiparissia orchards; Z. pullula in the Pelekanada orchard; and Koutsopodi and Ha. provincialis in the Kiparissia field. In contrast, a sweep net is more efficient for capturing larger, less active species, including potential vectors of X. fastidiosa. P. spumarius was collected in low numbers in almost every field with Malaise traps, while capturing with a sweep net was dominant in both fields in which this trapping method was used. N. campestris was collected in small numbers in the Lesvos and Peloponnese fields with a Malaise trap and it was dominant with a sweep net in the Pirgos field. Additionally, this study contributed new distribution data for several species, including the first records of Hecalus storai and Exitianus nanus in Greece. These findings expand the known distribution of Auchenorrhyncha in Greece and highlight the importance of continued biodiversity monitoring.

Further studies should investigate the preferred plant species for P. spumarius oviposition and nymphal development, which could be used as a management tool to suppress its population, if necessary. The potential bivoltine cycle of P. spumarius could increase the effectiveness of X. fastidiosa transmission if the bacterium is established in Greece. This, in turn, may complicate efforts to control the population of these vectors.