The emergence of Xylella fastidiosa (Xf) in the Balearic Islands in October 2016 was a major phytosanitary challenge with international implications. Immediately after its detection, eradication and containment measures included in Decision 2015/789 were implemented. Surveys intensified during 2017, which soon revealed that the pathogen was widely distributed on the islands and eradication measures were no longer feasible. In this review, we analyzed the control measures carried out by the Balearic Government in compliance with European legislation, as well as the implementation of its control action plan. At the same time, we contrasted them with the results of scientific research accumulated since 2017 on the epidemiological situation. The case of Xf in the Balearic Islands is paradigmatic since it concentrates on a small territory with one of the widest genetic diversities of Xf affecting crops and forest ecosystems. We also outline the difficulties of anticipating unexpected epidemiological situations in the legislation on harmful exotic organisms on which little biological information is available. Because Xf has become naturalized in the islands, coexistence alternatives based on scientific knowledge are proposed to reorient control strategies towards the main goal of minimizing damage to crops and the landscape.

Diaporthe amygdali is the causal agent of twig canker and shoot blight disease on almond. The main objective of this study was to elucidate the effect of weather variables on the D. amygdali inoculum in almond orchards in Mediterranean conditions. For that purpose, a quantitative PCR assay for the detection and quantification of D. amygdali was developed. This methodology was used to detect and quantify the inoculum of D. amygdali in spore traps placed at two almond orchards from different locations in two growing seasons (2019 to 2020 and 2020 to 2021). Weather variables were also recorded. Two-part hurdle models, which include a qualitative part (Bernoulli), with a binary response, and a quantitative part (Gamma), were used to study the relationships of the DNA concentration of D. amygdali on the traps with weather variables. The temperature effect was related to the daily thermal amplitude; narrower thermal ranges increased DNA detection, whereas wider thermal ranges reduced DNA concentration. Average relative humidity higher than 80% had a negative effect on the concentration of D. amygdali DNA. Rainfall had a positive influence on both parts of the model, confirming the contribution of precipitation to the inoculum abundance. Finally, wind speed positively influenced both parts of the models in both growing seasons. The relationships between weather variables and the inoculum of D. amygdali will assist with developing a decision support system to optimize the management of twig canker and shoot blight disease on almond.

Xylella fastidiosa (XF) is a Gram-negative bacterium responsible for severe plant diseases affecting a wide range of host plants, some of them important crops. Since 2017, only the pauca subspecies (ST80) have been identified in Ibiza. XF is naturally transmitted by xylem sap-feeding insects; among them, only Philaenus spumarius (PS) and Neophilaenus campestris Fallén (NC) have been reported as potential insect vectors for XF in Ibiza. This study aims to investigate the dissemination of XF and to propose effective control strategies. The crops and the surrounding vegetation were sampled for potential vectors. DNA from insects was extracted and amplified by three qPCR methods, allowing subspecies identification. The results confirmed the continuous presence of adults of PS and NC in Ibiza and Formentera from May to December with important populations. During the summer period, PS captures predominantly took place within the surrounding woody vegetation adjacent to the plots. The main host plant for PS was Pinus halepensis Miller in Ibiza and Juniperus phoenicea subsp. turbinata (Guss.) Nyman in Formentera. In Ibiza, off the total PS captures, 4.47% tested positive for XF. These results confirm that PS is the main vector of XF on these islands, both in terms of captures and the percentage of positive insects for XF. In Formentera, despite the presence of potential vectors and the proximity and contact with Ibiza, no XF-positive insects were found, confirming the absence of the bacterium on the island.

Understanding the spread of Xylella fastidiosa (XF) in agroforestry systems is key to reducing its ecological and economic impact. In Minorca (Balearic Islands), the subspecies multiplex (ST81) was detected for the first time in 2017, mainly affecting wild olive (Olea europaea var. sylvestris), a key species in Mediterranean shrublands. This study analyzes XF dynamics and its insect vectors, Philaenus spumarius (PS) and Neophilaenus campestris (NC), over three years (2019–2021) in six agroecosystems. A total of 621 Auchenorrhyncha specimens were collected and analyzed by qPCR. XF was detected in 11.88% of PS but not in NC. PS was predominantly captured on herbaceous cover and Pistacia lentiscus and less often on wild olive and Rhamnus alaternus. Infection rates in PS peaked in summer and autumn, reaching over 50% in some months, especially on wild olives. XF was also confirmed in wild olive in all plots, with infection rates between 10% and 55%. No phytoplasmas were found. These results highlight the major role of PS in XF transmission in Minorca, with wild olive as a key reservoir. The findings stress the importance of vector behavior, host plants, and landscape structure in managing XF in Mediterranean agroforestry systems, indicating migration to woody hosts as a key factor.