Crescenza Dongiovanni

Phenotypic response to twig canker and shoot blight varies substantially across almond germplasm. We hypothesized that genetically diverse almond accessions grown in a common orchard environment would exhibit genotype-dependent differences in symptom severity under natural disease pressure. Thirty-three almond accessions of different geographic origins were evaluated under field conditions in southern Italy. Disease incidence and severity were assessed, and symptomatic tissues were subjected to mycological and molecular analyses. Significant differences among accessions were detected for both disease incidence (I) and McKinney’s Disease Index (McK). ‘Merced’, ‘Nonpareil’, and ‘Genco’ exhibited high levels of disease incidence and severity, characterized by twig canker, shoot blight, and shoot clustering, with incidence values of 50% or higher, whereas local or less widely cultivated genotypes such as ‘Vesta’ and ‘Rana Gentile’ showed low disease incidence and severity. The Diaporthe complex represented the predominant fungal group isolated from symptomatic tissues, with D. foeniculina accounting for more than 80% of the identified Diaporthe isolates, whereas D. rudis was detected at lower frequencies. Other fungal taxa, particularly Botryosphaeriaceae, were recovered at lower frequencies. The observed variability supports the use of almond germplasm collections to identify genotypes with reduced symptom expression that may support breeding programs aimed at improving disease resilience.

BACKGROUND: Olive quick decline syndrome (OQDS), caused by Xylella fastidiosa subsp. pauca ST53, has devastated olive groves in Apulia (southern Italy), severely impacting olive production and rural agroecosystems. High populations of the key insect vector Philaenus spumarius (Hemiptera: Aphrophoridae) and agricultural landscapes dominated by susceptible olive cultivars have driven epidemic spread. Replanting with resistant olive cultivars is currently supported as a key restoration strategy for olive growers and olive oil industry. This study evaluated the transmission efficiency of X. fastidiosa ST53 by P. spumarius from and to resistant olive cultivars Leccino and FS17 compared with susceptible ones, using field and controlled experiments conducted over 3 years. RESULTS: Resistant olive cultivars acted as poor bacterial sources for vector acquisition, resulting in very low subsequent inoculation rates of the bacterium. In contrast, as recipient plants, resistant and susceptible cultivars were infected at similar rates, indicating that inoculation efficiency of infectious vectors did not differ among olive genotypes. Inoculation success was primarily influenced by the number of infectious insects feeding on recipient plants, whereas acquisition depended mainly on bacterial load in source plants, which was consistently lower in resistant cultivars. CONCLUSIONS: The presence of resistant olive varieties into agricultural landscapes could notably reduce epidemic spread by limiting vector infectivity and pathogen availability for transmission. However, vector population control and inoculum reduction remain essential components of effective OQDS management. These findings support integrated management strategies combining host resistance and vector management and provide valuable parameters for epidemic modelling and disease control planning. © 2026 Society of Chemical Industry.

Xylella fastidiosa subsp. pauca (Xfp) is the causal agent of olive quick decline syndrome (OQDS), a devastating disease threatening olive groves in Apulia, Italy. Efforts are underway to identify effective strategies to limit its spread. In this study, two biopesticide formulations, one derived from an onion extract rich in organosulfur compounds and the other based on the bacterium Paraburkholderia phytofirmans strain PsJN, were tested under field conditions. Treatments were applied eight times per year over a four-year period to assess their potential to reduce Xylella populations and disease progression. The results indicated that neither formulation lowered Xylella populations. Nonetheless, after four years of experimentation, the formulated PsJN treatment reduced both newly developed and pre-existing Xfp symptoms when applications started at the early stages of infection. In contrast, no effect was observed when treatments were applied to trees already exhibiting widespread infection and severe symptoms. Physiological analyses of stomatal conductance revealed that both treatments alleviated the drought stress associated with Xfp infection, with the formulated PsJN treatment showing statistically significant improvements. Consistently, treated olive trees exhibited higher stomatal conductance and lower canopy temperatures compared with untreated controls. Based on these encouraging results, further studies are needed to explore the use of these products under different conditions and application timings, as well as in combination with other treatments, to support the development of an integrated management strategy for controlling infections.

Background: During storage, fruits and vegetables are susceptible to the pathogens responsible for postharvest decay. Various tools are available to manage these issues, but not all are environmentally sustainable. Low-temperature plasma (LTP) has garnered significant attention among the most promising and eco-friendly solutions. LTP can be applied directly or indirectly, offering versatile applications. One notable indirect application is the utilization of plasma-activated water (PAW). In this study, we investigated the efficacy of an aerosol made by droplets of water nebulized by the effluent gases of a plasma discharge as a delivery method of PAW to substrates. We named this novel application, reported for the first time, plasma-activated fog (PAF). In this work, it was tested as a new alternative technology for fruit decontamination against postharvest fungal pathogens and pesticide residues. Results: PAF was generated via volume dielectric barrier discharge (VDBD) in a jet-like configuration and was applied to evaluate the in vitro effects on the conidial germination of major fungal postharvest pathogens, such as Alternaria alternata , Aspergillus carbonarius , Botrytis cinerea , Cladosporium sp., Monilinia fructicola , Penicillium italicum , Penicillium expansum and Rhizopus sp. Differences in fungal sensitivity to PAF were recorded, with A. alternata showing the lowest sensitivity to treatments. For most species, complete spore inhibition was obtained after 3–5 min of exposure. The efficacy of PAF against fungal rot was assessed on table grapes and strawberries, revealing a reduction in the percentage of rotted fruits exposed to 10 min of treatment, ranging from 45 to 80% on table grapes and from 52 to 74% on strawberries. PAF treatments also reduced pesticide residues on grape bunches and strawberry fruits, with various results depending on the active ingredient, with reductions of up to 96% for abamectin among insecticides and acaricides, and up to 38% for the fungicide fenhexamid. Conclusions: The results obtained in the present work have the potential to refine and optimize PAF treatment conditions for the antimicrobial decontamination of plant products. Graphical

Since its first detection in 2013, Xylella fastidiosa subsp. pauca (Xfp) has caused a devastating Olive Quick Decline Syndrome (OQDS) outbreak in Southern Italy. Effective disease surveillance and treatment strategies are urgently needed to mitigate its impact. This study investigates the short-term (1.5 years) effects of thymol-based treatments on infected olive trees of the susceptible cultivar Cellina di Nardò in two orchards in Salento, Apulia region. Twenty trees per trial received a 3% thymol solution either alone or encapsulated in a cellulose nanoparticle carrier. Over two years, sap flux density and canopy-transmitted solar radiation were monitored using TreeTalker sensors, and spectral greenness indices were calculated. Xfp cell concentrations in plant tissues were quantified via qPCR. Neither thymol treatment halted disease progression nor significantly reduced bacterial load, though the Xfp cell concentration reduction increased over time in the preventive trial. Symptomatic trees exhibited increased sap flux density, though the treatment mitigated this effect in the curative trial. Greenness indices remained lower in infected trees, but the response to symptom severity was delayed. These findings underscore the need for longer-term studies, investigation of synergistic effects with other phytocompounds, and integration of real-time sensor data into adaptive disease management protocols.

Two experiments were carried out to verify the susceptibility of olive plantlets of the Xylella fastidiosa - resistant cultivar Favolosa to the root-knot nematode Meloidogyne javanica and the root lesion nematode Pratylenchus vulnus. In the first experiment the relationship between the nematode population density and the olive plants growth was assessed. Plant growth parameters, main shoot length and diameter and number of nodes, were analysed by the SeinFit program in order to calculate the tolerance limit (T) to the nematode attack and the minimum relative per cent growth (m) of the plants. In the second trial, the reaction of olive plantlets to P. vulnus was assessed by measuring the growth parameters after P. vulnus inoculations (200 juveniles/plant). The susceptibility to the nematode was evaluated on the base of the reproduction factor r = Pf/Pi according to r value: NH(non host)=Pf<Pi; P(weak host) = Pi300 nematodes/plant. For each trial ten replications were considered. Both trials indicated a susceptibility of the cv. Favolosa to both phytoparasitic nematodes despite of its resistance to Xylella fastidiosa.

Following the detection of the quarantine bacterium Xylella fastidiosa (Wells et al.) in the Apulia region (southern Italy) and the identification of spittlebugs as the main vector species that contributes to its epidemic spread, monitoring activities have been intensified in an attempt to implement vector control strategies. To date, sweep nets have been the most widely used sampling method to monitor adult spittlebug populations. Field experiments were carried out, during 2018 and 2019, to evaluate the effectiveness of sticky traps in capturing spittlebugs in different woody crops. The attractiveness of different traps was compared: four colored sticky traps (white, red, blue, and yellow), with the yellow sticky traps having three different background patterns (plain yellow, yellow with a black circle pattern, and yellow with a black line pattern). In addition, the efficiency of the yellow sticky traps was evaluated by placing the traps on the ground or hanging them from the canopies in orchards with different spittlebug population densities. Trap catches of Philaenus spumarius (Linnaeus) and Neophilaenus campestris (Fallén) (Hemiptera: Aphrophoridae) were compared with those collected using sweep nets. The two spittlebug species showed a similar response to the colored traps and were mainly attracted to the yellow sticky traps. Captures throughout the adult season indicated that an accurate estimation of the presence and abundance of spittlebugs can be obtained by integrating the two sampling methods. Moreover, sweep nets appeared to be more efficient in collecting adults soon after their emergence, while the use of sticky traps was more efficient in the rest of the adult season when the use of traps can significantly expedite vector monitoring programs.

Spatial-temporal dynamics of spittlebug populations, together with transmission biology, are of major importance to outline the disease epidemiology of Xylella fastidiosa subsp. pauca in Apulian olive groves. The spread rate of X. fastidiosa is mainly influenced by (i) the pathogen colonization of the host plant; (ii) the acquisition of the pathogen by the vector from an infected plant, and its inoculation to healthy plants; (iii) the vector population dynamics and abundance at different spatial scales; and (iv) the dispersal of the vector. In this contribution we summarize the recent advances in research on insect vectors’ traits—points ii, iii, and iv—focusing on those most relevant to X. fastidiosa epidemic in Apulia. Among the vectors’ bioecological traits influencing the X. fastidiosa epidemic in olive trees, we emphasize the following: natural infectivity and transmission efficiency, phenological timing of both nymphal and adult stage, the role of seminatural vegetation as a vector reservoir in the agroecosystem and landscape, and preferential and directional dispersal capabilities. Despite the research on X. fastidiosa vectors carried out in Europe in the last decade, key uncertainties on insect vectors remain, hampering a thorough understanding of pathogen epidemiology and the development of effective and targeted management strategies. Our goal is to provide a structured and contextualized review of knowledge on X. fastidiosa vectors’ key traits in the Apulian epidemic, highlighting information gaps and stimulating novel research pathways on X. fastidiosa pathosystems in Europe. [ ] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .