## 1 Introduction  
The plant-pathogenic _Xylella fastidiosa_ (_Xf_; _Lysobacteraceae_ family [1]) is a Gramagegative, affagellate, xylem-limited _Gammaproteobacteriaum_, is native of the Americas, and is plant-to-plant transmitted by xylem sap-feeding insects. It currently affects almost 700 plant species belonging to 88 families [2] and causes serious diseases in crops of high economic importance, including, as follows: grapevine (Pierce's disease, PD); citrus (citrus variegated chlorosis, CVC); almond (almond leaf scorch disease, ALSD); and olive (olive quick decline syndrome, OQDS). Bacterial cell aggregates, attached to the xylem vessels along with tyloses and gums produced by the plant as an attempt to entrap the pathogen, cause vessel occlusion and a deficit of the sap carriage [3]. This results in the impairment of the water flux and generates visible symptoms like leaf scorching, twig desiccation, and gradual plant dieback. In almonds, ALSD [4] appears as a marginal scorching of leaves that begins as early as June and continues to develop during summer, when temperatures and water demand increase [5]. A peculiar golden-yellow band develops between the brown necrotic edge and the inner green tissues of the leaf. The whole canopy of the tree becomes seriously affected, showing a typical golden-brown appearance (known as 'golden death'; [6]). Infected trees bloom and leaf out later than healthy trees, are stunted, less productive, and have reduced terminal growth [7; 8]. The first \(X\!f\) outbreak in the Balearic Islands dates to October 2016, when cherry trees (_Prunus avium_ L.) and _Polygala myrifolia_ L. plants were found to be infected by \(X\!f\) subsp. _fastidiosa_ strain ST1 [9; 10]. After this first record, subsequent surveys revealed that the bacterium was widespread on other islands in the archipelago. Indeed, through the years, the Balearic Islands Official Plant Health Laboratory (LOSVIB) also detected new sequence types (STs) belonging to the subspecies _multiplex_ (\(X\!f\)m; ST7 and 81; [11]) and _pauca_ [\(X\!f\)p, ST80 [12]) in symptomatic almond trees scattered across the islands [13]; lately, ST53 has been detected in olive trees in Mallorca ([[https://www.europpress.es/illes-balears/noticia-balears-presenta-nuevo-plan-contencion-xplela-detectar-subespecie-mallorca20240201135](https://www.europpress.es/illes-balears/noticia-balears-presenta-nuevo-plan-contencion-xplela-detectar-subespecie-mallorca20240201135)]([https://www.europpress.es/illes-balears/noticia-balears-presenta-nuevo-plan-contencion-xplela-detectar-subespecie-mallorca20240201135](https://www.europpress.es/illes-balears/noticia-balears-presenta-nuevo-plan-contencion-xplela-detectar-subespecie-mallorca20240201135)) 337.html; accessed on 15 June 2024). Currently, about 80% of almond trees in Mallorca are compromised [14] since the containment strategies established by the Balearic Islands government were ineffective and failed to reduce disease spread [15]. This has caused a significant alteration to the rural landscape of the whole island and has reduced almond production by 20-40%, depending on the cultivar [16]. The management of \(X\!f\) infections mostly relies on the prompt eradication of infected sources and control of the vector insect population. In this strategy, early detection of the bacterium is of paramount importance to limit its spread. Hence, an efficient containment requires point-of-care (PoC) tests with a short turnaround time, a low cost, and high accessibility. Molecular detection, mainly based on real-time quantitative PCR performed on purified DNA, is considered the gold standard because of its specific and sensitive identification of the bacterium at low titers and also in symptomless trees.