Characterization of Spanish Olive Virome by High Throughput Sequencing Opens New Insights and Uncertainties

The use of high throughput sequencing (HTS) for the analysis of Spanish olive trees showing leaf yellowing discoloration, defoliation, and/or decline has provided new insights into the olive viruses present in Spain and has opened discussions about the pros and cons of these technologies for diagnostic purposes. In this study, we report for the first time in Spanish orchards the presence of olive leaf yellowing-associated virus (OLYaV), for which the second full coding sequence has been determined. This virus has also been detected in a putative vector, the psyllid Euphyllura olivina. In addition, the presence in Spain of Olea europaea geminivirus (OEGV), recently reported in Italy, has been confirmed, and the full-length sequence of two isolates was obtained by HTS and Sanger sequencing. These results, as well as the detection of other viral sequences related to olive latent virus 3 (OLV-3) and olive viral satellite RNA, raises questions on the biological significance of the findings, about the requirement of standardization on the interpretation of HTS results, and the necessity of additional tests to confirm the relevance of the HTS detection of viral sequences.

Population dynamics, seasonal fluctuations and spatial distribution of the olive psyllid Euphyllura olivina Costa (Homoptera, Psyllidae) in Algeria

The olive psyllid Euphyllura olivina Costa (Homoptera, Psyllidae) causes considerable damage in olive groves in the Mediterranean basin, there by affecting production. To assess the rate of infestation and provide elements of integrated pest management, we monitored the life cycle and bio–ecology of this pest through population counts on the leaves and twigs of the tree from 29 March 2019 to 27 March 2020 at two relatively distant olive farms (Ain fares and Oued taria) in the wilaya of Mascara, Algeria. Our results showed that infestation was high on trees in the Oued taria farm. We found that E. olivina developed two generations per year, in spring, influenced by the climatic factors. The difference between the relative abundance of the different life stages (eggs, larval instar 1, 2, 3, 4 and 5, female and male) in the cardinals orientations was significant. Infestation was highest on the southern and central orientations of the tree. Populations fluctuations were significantly affected by season at both farms.

Adoption of Olive Farmers to the Integrated Pest Management Techniques in the Syrian Coastal Region

Sakr, L.M., M.J. Al-Abdallah and A.N.M. Bashir. 2021. Adoption of Olive Farmers to the Integrated Pest Management Techniques in the Syrian Coastal Region. Arab Journal of Plant Protection, 39(1): 69-78. A survey was conducted to investigate adoption of integrated pest management (IPM) approaches by olive farmers, through determining their knowledge about the most important olive pests in the Syrian Coastal Area, and the relationship between growers’ personal traits and their adoption of IPM approaches. This evaluation was carried out in 42 villages in Tartus and Lattakia governorates along the Syrian coast in 2017 and 2018 growing seasons. Data were collected through face-to-face interviews with a random sample of 420 olive growers by using a questionnaire designed for the purpose of this study. Collected data on frequencies, percentages, averages, standard deviations, relative importance index, in addition to correlation coefficients, were used for data analysis. Results showed that: the Spilocaea oleagina (Cast.), Bactrocera oleae (Rossi), Prays oleae (Bernard) and Euphyllura olivina (Costa) were the most prevalent pests in the researched area, whereas Margaronia unionalis (Hubner), Leveillula taurica (Lév.), and Phloeotribus scarabaeoides (Bernard) were less common. Almost 57.78 and 32.8% of farmers had medium level of IPM adoption in Tartus and Lattakia governorates, respectively. Positive significant correlation was found between adoption levels and each of degree of participation in extension activities and knowledge levels, whereas negative significant correlation was found between adoption levels and each of land property fragmentation and constraints of IPM implementation. Based on this findings it can be concluded that extension activities need to be intensified and more emphasis should be placed on training programs to improve growers’ knowledge and adoption of the concepts and applications of IPM practices. Keywords: Integrated pest management, olive growers, Syrian coast, knowledge diffusion level, adoption.

Identification of fungi in Tunisian olive orchards: characterization and biological control potential

Background Olive production is the main agricultural activity in Tunisia. The diversity of fungi was explored in two different olive groves located in two distant geographical zones in Sfax (Tunisia) with different management practices. Results Fungal isolation was made from soil and the major olive tree pests, namely the Olive fly, Bactrocera oleae Gmelin (Diptera: Tephritidae), and the Olive psyllid, Euphyllura olivina Costa (Homoptera: Psyllidae). A total of 34 fungal isolates were identified according to their phenotypic, genotypic, biochemical and biological activities. Twenty fungal species were identified belonging to six different genera (Alternaria, Aspergillus, Cladosporium, Fusarium, Lecanicillium and Penicillium) by the analysis of their ITS1–5.8S–ITS2 ribosomal DNA region. Different bioassays performed in this work revealed that 25/34 (73.5%) of the identified fungal isolates showed an entomopathogenic and/or antagonistic activity, 9/34 (26.5%) of them displayed phytopathogenic features. Conclusions Fungal species that showed entomopathogenic and/or antagonistic potentialities and that are non-phytopathogenic, (17/34; 50%) of our fungal isolates, could be explored for olive protection against fungal diseases and pests, and might have a future application as biocontrol agents.

Current Distribution of the Olive Psyllid, Euphyllura olivina, in California and Initial Evaluation of the Mediterranean Parasitoid Psyllaephagus euphyllurae as a Biological Control Candidate

The olive psyllid, Euphyllura olivina, is a newly invasive species to California with the potential to become an economical pest if it reaches the olive production regions of California’s Central Valley. Here, we report on surveys undertaken in California to assess the psyllid’s current distribution and the occurrence of parasitism. Additionally, we present results of foreign collections of its parasitoids and initial non-target studies of a possible biological control agent, the Mediterranean parasitoid Psyllaephagus euphyllurae. The current distribution of the psyllid appears to be limited to the California coast between Monterey and San Diego; there have been no reports of infestations on olives in the major production areas of central and northern California. Psyllaephagus euphyllurae was the major primary parasitoid found in our foreign collections. The potential non-target impact of P. euphyllurae was tested on three native North American psyllid species: Neophyllura arctostaphyli, Euglyptoneura nr. robusta, and Calophya nigrella. No P. euphyllurae developed on the non-target species during no-choice tests. Behavioral observations in choice tests confirmed no attack on the non-target hosts, although the parasitoid did remain longer on N. arctostaphyli-infested manzanita plants, and revealed no host feeding behavior.

Diversity of insects associated with olive (Oleaceae) groves across a dryland climate gradient in Algeria

This study investigated insect diversity of olive (Olea europaea Linnaeus (Oleaceae)) groves grown in arid and semiarid climates in northeastern Algeria. Using several sampling techniques, a total of 1326 insect specimens were collected and identified into 151 species, 124 genera, 65 families, and 10 orders. Hymenoptera and Coleoptera were quantitatively the most abundant, whereas the dominant functional feeding groups were phytophages then predators. The entomofauna included several olive pests such as Bactrocera oleae (Rossi) (Diptera: Tephritidae), Parlatoria oleae (Colvée) (Hemiptera: Diaspididae), Euphyllura olivina (Costa) (Hemiptera: Liviidae), and Liothrips oleae Costa (Thysanoptera: Phlaeothripidae). Although insect diversity parameters recorded for both observed and expected species richness were higher in olive groves grown under semiarid compared with arid climate, the completeness rate of species richness obtained using the nonparametric incidence estimators was higher in arid olive groves. Generalised linear models showed that the number of individuals and species richness varied significantly between climates (P < 0.01), whereas the variation of the rest of diversity parameters was not significant. Diversity traits of insect assemblage of each climatic region were positively correlated. Besides, the Mantel permutation test revealed similar patterns (r = 0.91, P < 0.0001) between correlation matrices of the two climates. When increasing the number of samples, species richness extrapolation revealed that diversity is expected to increase by 130% in olive groves grown under arid climate and 93% in semiarid climate. These increases are related to continuous appearance of rare and scarce insects as demonstrated by species rarefaction curves. Even with high evenness values of insect communities, similarity was low between climate indicating the rarity and scarcity of populations.