This study compared sustainable, low-copper strategies with conventional fungicides for controlling olive leaf spot (Venturia oleaginea), focusing on defoliation, visual and latent incidence, and leaf anatomical responses. Alternative compounds, including copper gluconate, a low-copper content product, and a combination of a lowcopper content product with diatomaceous earth, were tested against a Bordeaux mixture and copper oxychloride standard. All alternative treatments reduced defoliation compared to the untreated control. The synergy between the low-copper content product and diatomaceous earth resulted in the greatest leaf persistence (40%) and the lowest infection intensity on older leaves during spring. A significant negative correlation (r = -0.493) between palisade thickness and symptomatic intensity suggests these treatments may enhance structural resistance by thickening mesophyll layers. Furthermore, primary infections on new growth were recorded as early as July, triggered by summer dew moisture, indicating an epidemiological shift under changing climatic conditions. These findings demonstrate that low-copper content products, supplemented by biostimulants and physical barriers, provide protection equivalent to conventional standards while reducing copper accumulation, aligning Mediterranean olive production with EU strategic goals.

The olive fruit fly, Bactrocera oleae (Rossi), is the most economically important pest of the olive tree; the fly prefers some cultivars over others, although the reason for this is still unclear. Current research results indicate that volatile compounds of the olive tree have a greater influence on the fly's attraction to a host plant than the physical parameters of the olive fruit. Therefore, the aim of the study was to investigate the relationship between the degree of the olive fruit fly infestation and the volatiles released by the olive leaves and fruits of three cultivars with similar physical fruit parameters, grown in the same olive grove. Lastovka, Frantoio and Leccino cultivars were studied, HS-SPME/GC-MS was performed to determine the profile of volatiles in leaves and fruits and to investigate the relationship between volatiles and the olive fruit fly infestation. Frantoio was the olive cultivar with the highest infestation by the olive fruit fly (39.66 %), followed by Leccino (24 %) and Lastovka (5 %). Among total number of volatiles identified in the study (55), more were detected in the fruits (37) than in the leaves (26). Saturated hydrocarbons and terpenes were the most abundant volatile groups in the fruits, while terpenes were found the most abundant in the leaves. The amounts of (E)-4,8-dimethylnona-1,3,7-triene E )-4,8-dimethylnona-1,3,7-triene and heneicosane were highest in the olive fruits of all cultivars tested. Heneicosane and eicosane were mainly released from ripe fruits and strongly correlated with the degree of infestation with the olive fruit fly. In addition, henicosane was the most abundant volatile compound in ripe fruits, along with 2,6-di-tert-butyl-4-methylphenol. Therefore, the results of the study suggest that fruit-derived volatiles have the greatest impact on the attraction of the olive fruit fly. The use of plant volatiles as attractants could be an effective tool for the sustainable control of olive trees to reduce the damage caused by the olive fruit fly while avoiding negative impacts on the environment and biodiversity.

The objective of this study was to evaluate the release rate, duration, and biological efficiency of yeast volatile compounds associated with olive fruit flies in slow-release dispensers, polypropylene vials, and rubber septa attached to yellow sticky traps under different environmental conditions in order to protect the environment, humans, and nontarget organisms. Isoamyl alcohol, 2-octanone, and 2-phenethyl acetate were placed in dispensers and tested over a four-week experiment. The weight loss of the volatile compounds in both dispensers was measured, and a rapid, inexpensive, and simple HS-GC/FID method was developed to determine the residual amount of volatiles in the septa. 2-Phenethyl acetate stood out in the rubber septa and showed a statistically significant difference in the release ratio compared to the other volatiles under all conditions tested. Our results showed that the attraction of olive fruit flies increased with decreasing concentrations of the tested volatiles. Regarding the number of flies attracted by rubber septa containing 2-phenethyl acetate, significantly better results were obtained than for septa containing isoamyl alcohol and 2-octanone, in contrast to the attraction of olive fruit flies to polypropylene vials containing these compounds but without significant difference. Since the presence of all tested chemicals was detected during the experiment, this opens the possibility of using more environmentally friendly and cost-effective dispensers with a significantly lower amount of semiochemicals.

Even though Olea europaea L. is one of the most important and well-studied crops in the world, embryonic parts of the plants remain largely understudied. In this study, comprehensive phytochemical profiling of olive vegetative buds of two Croatian cultivars, Lastovka and Oblica, was performed with an analysis of essential oils and methanol extracts as well as biological activities (antioxidant, antimicrobial, and cytotoxic activities). A total of 113 different volatiles were identified in essential oils with hydrocarbons accounting for up to 60.30% and (Z)-3-heptadecene being the most abundant compound. Oleacein, oleuropein, and 3-hydroxytyrosol had the highest concentrations of all phenolics in the bud extracts. Other major compounds belong to the chemical classes of sugars, fatty acids, and triterpenoid acids. Antioxidant, antimicrobial, and cytotoxic activities were determined for both cultivars. Apart from antioxidant activity, essential oils had a weak overall biological effect. The extract from cultivar Lastovka showed much better antioxidant activity than both isolates with both methods (with an oxygen radical absorbance capacity value of 1835.42 μM TE/g and DPPH IC50 of 0.274 mg/mL), as well as antimicrobial activity with the best results against Listeria monocytogenes. The human breast adenocarcinoma MDA-MB-231 cell line showed the best response for cultivar Lastovka bud extract (IC50 = 150 μg/mL) among three human cancer cell lines tested. These results demonstrate great chemical and biological potential that is hidden in olive buds and the need to increase research in the area of embryonic parts of plants.

A capacity to determine the provenance of high-value food products is of high scientific and economic interest. With the aim to develop a tool for geographical traceability of Croatian extra virgin olive oils (EVOO), multielement composition and 13C/12C isotope ratio in EVOO as well as the geochemistry of the associated soils were analysed in samples collected from three regions along the Croatian Adriatic coast. Soil geochemistry was shown to influence the transfer and elemental composition of EVOO. The most discriminating variables to distinguish EVOO from different regions were S, Mo, Rb, Mg, Pb, Mn, Sn, K, V and δ13C. The predictive models achieved high sensitivity and specificity, especially when carbon isotope composition was added. The results suggest that interregional geographical traceability of Croatian EVOO is possible based on matching their multielement composition with that of the soils in the provenance area.

The olive fruit fly, Bactrocera oleae (Rossi) is economically the most important olive pest, causing yield losses in all olive growing areas where is detected. Considering that EU requires the reduction of pesticide use by up to 100% by 2050, more effective non-pesticide lures for B. oleae monitoring and/or controlling are needed. This research was aimed at investigating the attractiveness of different blends of olive fruit fly-associated yeast volatiles toward B. oleae. Three blends of olive fruit fly-associated yeast volatiles: isoamyl alcohol and 2-phenethyl alcohol; isoamyl alcohol, 2-phenethyl alcohol and 2-phenethyl acetate; and isoamyl alcohol, 2-phenethyl acetate and isobutyl acetate were selected and tested on yellow sticky traps for attraction of B. oleae in olive orchard. Results showed that traps containing all tested blends of olive fruit fly-associated yeast volatile compounds, in total, were significantly more attractive to B. oleae and were not significantly attractive to green lacewings, compared to the control. Among them, the most promising was the one containing the blend of isoamyl alcohol, 2-phenethyl acetate and isobutyl acetate because its attractiveness was constantly significant during investigation compared to the others. This blend in the future could lead us to the discovery of a new attractant for the monitoring and/or controlling of B. oleae.

A single phenolic group and even a compound play different roles in the sensory properties and stability of virgin olive oil (VOO), which in turn are strongly influenced by several factors. Understanding the causes of differences in phenolic compound composition and oxidative stability (OS) in VOOs is essential for targeted and timely harvest and processing while maintaining desired oil quality. The phenolic profile and OS of two monocultivar VOOs (Oblica and Leccino) grown in two geographical sites of different altitudes (coastal plain and hilly hinterland) were analyzed throughout the ripening period over two years. Concentration of secoiridoids was 30% higher in the Oblica than in the Leccino VOOs, which in turn had significantly higher values of OS. Both cultivars had more than twice as high concentrations of the two most abundant phenolic compounds, the dialdehyde form of decarboxymethyl oleuropein aglycone and the dialdehyde form of decarboxymethyl ligstroside aglycone, and OS values in a colder growing site of higher altitude. Among the studied monocultivar VOOs, the secoiridoid group did not behave equally during ripening. The hierarchy of different influencing factors was investigated using multivariate statistics and revealed: cultivar > geographical site > harvest period > growing season. In addition, the possibility of traceability of VOO using molecular markers was investigated by establishing SSR profiles of oils of the studied cultivars and comparing them with SSR profiles of leaves.

Olive leaves are a highly available by-product from table olive and olive oil production. They are nowadays strongly valuable for their major bioactive compounds and their beneficial effects. To determine the differences between two Croatian domestic (Lastovka, Oblica) and two introduced (Leccino, Frantoio) cultivars, physical and chemical analysis of olive leaves were performed: surface area, color variability, total phenolic amounts, and essential oil volatile profiles were analyzed at three harvest periods. All cultivars greatly differed in surface area, with cv. Lastovka being the smallest. Color variability resulted in an overall decrease in darkness and amounts of green and yellow that could be attributed to a decrease in photosynthetic demand and chlorophyll content. The highest amount of total phenolic content occurred in the summer months, followed by a reduction until October. Essential oils volatiles were determined by GC-MS and showed great diversity not only amongst cultivars but also between harvest periods, with overall 45 compounds identified. Principal component analysis distinguished domestic cultivar Oblica from the other observed cultivars, mainly due to its essential oil volatile fingerprint. Compounds that differentiated cv. Oblica were aldehydes ((E,Z)-2,4-heptadienal, (E,E)-2,4-heptadienal, decanal), ketones ((E)-β-damascone, dihydrodehydro-β-ionone), sesquiterpenes (cyclosativene, α-copaene, α-muurolene) and saturated hydrocarbons (tetradecane, hexadecane). Essential oil volatile fingerprint attributed the highest to the biodiversity of domestic cv. Oblica through all three harvest periods.

A potential of rare earth elements (including yttrium) (REY) accumulation in olives is increasing due to enhanced use of REY in human activities. REY transfer to extra virgin olive oil (EVOO) is little studied, and characterising the relationships between soil properties and REY concentrations in olive leaves, pomace and EVOO can enhance our understanding of soil-plant interactions. Three different soil types (reclaimed karst, rendzina and cambisols), with the sum of REY concentrations (54–364 μg g−1) among the highest in European soils, were characterized for their pH, organic carbon, total carbonates and the applied agronomic practice. Aluminium, calcium, iron, phosphorus and REY were determined in soil (total and plant-available), olive leaves, pomace and EVOO. REY were mainly excluded from plant uptake and only small amounts of REY were transferred to leaves (0.2–652 ng g−1), pomace (0.001–10 ng g−1) and EVOO (<0.5–33 pg g−1). Soil REY availability (0.001–1685 ng g−1) and plant uptake increased with increasing soil acidity. Leaf REY concentrations were mainly explained by plant-available REY and pH. There was an indication of enhanced REY plant availability being associated with low available phosphorus and soil ploughing. Soil properties influence REY uptake and further partitioning to leaves, fruits and EVOO.

The olive fruit fly, Bactrocera oleae (Rossi), is one of the most damaging insect pests of olives worldwide, requiring the use of insecticides for fruit protection in many orchards. Olive fruit flies are attracted to volatile composunds, including a female-produced pheromone, and host-plant and bacterial volatiles. Preliminary laboratory bioassays were conducted for olive fruit fly attraction to over 130 yeast strains from among 400 that were isolated from B. oleae adults and larvae or other insects, infested olives, and potential feeding sites. Kuraishia capsulata, Scheffersomyces ergatensis, Peterozyma xylosa, Wickerhamomyces subpelliculosus, and Lachancea thermotolerans appeared to attract B. oleae as well or better than did torula yeast pellets (Cyberlindnera jadinii; syn. Candida utilis). Volatile compounds emitted by these yeast strains were chemically identified, and included isobutanol, isoamyl alcohol, 2-phenethyl alcohol, isobutyl acetate, and 2-phenethyl acetate. The behavioral response of B. oleae adults to these volatile compounds at three concentrations was tested in a laboratory Y-tube olfactometer. The same volatile compounds were also tested in the field. Isoamyl alcohol was more attractive than the other compounds tested in both laboratory and field bioassays. Isobutanol was not attractive to B. oleae in either laboratory bioassay or field bioassay. Identifying yeast volatiles attractive to the olive fruit fly may lead to development of a more effective lure for detection, monitoring, and possibly control of B. oleae.

The olive fruit fly (Bactrocera oleae Rossi) is the primary insect pest in all olive-growing regions worldwide. New integrated pest management (IPM) techniques are needed for B. oleae to mitigate reliance on pesticides used for its control which can result in negative environmental impacts. More effective lures for monitoring olive flies would help to know when and where direct chemical applications are required. The aim of this research was to find new, more effective methods for B. oleae detection and monitoring. Twelve insect-associated yeasts were selected and tested as living cultures in McPhail traps for the attraction of olive flies. Certain yeasts were more attractive than others to B. oleae; specifically, Kuraishia capsulata, Lachancea thermotolerans, Peterozyma xylosa, Scheffersomyces ergatensis, and Nakazawae ernobii, than the industry-standard dried torula yeast (Cyberlindnera jadinii; syn. Candida utilis). The attractiveness of dry, inactive (i.e., non-living) formulations of these five yeasts was also tested in the field. Inactive formulations of K. capsulata, P. xylosa, N. ernobii, and L. thermotolerans were significantly more attractive to B. oleae than commercially available torula yeast. Green lacewing, Chrysoperla comanche (Stephens) (Neuroptera: Chrysopidae), adults were incidentally caught in traps baited with the live yeast cultures. This is the first field study that compares olive fly attraction to yeast species other than torula yeast. Commercialization of yeasts that are more attractive than the torula standard would improve monitoring and associated control of the olive fruit fly.

Many adult Chrysoperla comanche (Stephens) green lacewings were caught in traps baited with live yeast cultures during tests designed to catch olive fruit flies. All 13 yeast species tested were more attractive than the industry-standard dried torula yeast (Cyberlindnera jadinii; syn. Candida utilis). Live C. jadinii culture attracted significantly more lacewings than the inactive dried-pellet form of the same yeast species, demonstrating that volatiles from live yeast cultures attract adults of this lacewing. Odor profiles for two of the highly active yeasts tested herein (Lachancea thermotolerans and Solicoccozyma terrea) were similar to that for Metschnikowia pulcherrima, a yeast species isolated earlier from the gut diverticulum of Chrysoperla rufilabris. A new Metschnikowia species (M. chrysoperlae), along with two new Candida spp. that were recently realigned to one of the Metschnikowia clades (M. picachoensis and M. pimensis), were also identified from the diverticulum of C. comanche. Thus, one clade of Metschnikowia yeasts that commonly occur in floral nectar appears to exhibit mutualistic symbioses with Chrysoperla green lacewings. Both male and female C. comanche adults were attracted in the present study, and we speculate that males have exploited this symbiosis by offering Metschnikowia-laden regurgitant, including attractive volatiles, to females ('mating trophallaxis') as a nuptial gift.

Arthropods, within the olive tree canopy, which can act as bioindicators of different management systems (conventional, integrated and organic), were collected in costal Croatia during 2007-2009. The aim of the research was to determine the arthropod orders present in each of the observed olive groves, to identify the number of individuals in each order, and to set potential bioindicators of different management systems. In order to do that, arthropods were collected from the olive canopies at three locations (Supetar, Kaštel Stari and Duilovo). After the samples were sorted according to orders, and determined according to arthropods determination keys. Olive groves were characterised by the same growth conditions and environment, with differences in agricultural management systems. In this investigation, 7882 arthropods were collected, belonging to 17 orders. It was found that Diptera, Heteroptera and other Hemiptera individuals, excluded Cicadidae and Psyllidae family individuals, could be defined as potential bioindicators of olive groves under different management systems. The number of Araneae and Coleoptera individuals significantly differed in all researched olive groves. So, these orders can be considered as bioindicators of different management systems. The knowledge obtained in this research can potentially be exploited in olive production in the future. Obtained results represent an important contribution to the inventory of arthropods in olive canopy. Also, this research significantly improves understanding of both harmful and beneficial entomofauna in olive groves and consequently contributes to better understanding of the total entomofauna in Croatia.