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Early detection of Xylella fastidiosa outbreaks in Apulian olive groves is crucial, especially in buffer zones and pathogen-free areas where olive trees are asymptomatic. Three studies were conducted. Two were on the spatial and temporal progression of X. fastidiosa infections in tree canopies of asymptomatic or mildly symptomatic olive trees of tolerant (‘Leccino’) and susceptible (‘Cellina di Nardò’ and ‘Ogliarola salentina’) cultivars. Despite different trends in pathogen infection rates and concentrations between ‘Leccino’ and susceptible olive cultivars over the study period, results showed that sampling was most effective in the mid-upper part of tree canopies throughout the year, excluding the warmest and coldest periods. Stem xylem tissues were the most appropriate for detecting the pathogen compared to lower parts of mature leaves with petioles, using serological and molecular assays. Based on these results, a third study was conducted to compare molecular and serological tests (qPCR, real-time LAMP, DAS-ELISA, DTBIA) for detection of X. fastidiosa in the mid-upper part of asymptomatic branches of infected ‘Leccino’ trees that were sampled in an appropriate collection time, using stem xylem tissue as the most appropriate matrix for testing. The molecular methods showed the greatest sensitivity, with no undetermined results, while among the serological assays, DTBIA was more sensitive than DAS-ELISA. An improved protocol for monitoring asymptomatic olive trees is recommended.

Surveys for virus and virus-like diseases were carried out in commercial vineyards in the provinces of Rahovec and Suhareka of Kosovo. Samples were collected at random from 306 individual vines for laboratory testing. Leafroll and rugose wood symptoms were commonly observed in the field, whereas fanleaf symptoms were very rare. A total of 68% of ELISA-tested vines (208 out of 306) was infected by one (40.9%) or multiple (27.1%) viruses. The highest infection rate was found in Suhareka province (75%). Grapevine fleck virus (GFkV) was the most widespread (52.0%), followed by Grapevine leafroll-associated virus 3 (GLRaV-3, 18.3%), Grapevine leafroll-associated virus 1 (GLRaV-1, 15.7%), and Grapevine virus A (GVA, 11.1%). Other economically relevant viruses occurred rarely, i.e. Grapevine fanleaf virus (GFLV, 1.6%), Grapevine virus B (GVB, 1.0%) and Grapevine leafroll-associated virus 2 (GLRaV-2, 0.3%). Arabis mosaic virus (ArMV) was not found. Some of the most important grapevine varieties cultivated in Kosovo, i.e. Smederevka, Vranac, Prokupac, Italian Muskat, Muskat of Hamburg, and Italian Riesling, had average infection rates that ranged from 63% to 85%. In RT-PCR, Grapevine rupestris stem pitting associated virus (GRSPaV) was detected in 80.4% of the vines. Vein mosaic and vein necrosis symptoms were detected in graft-inoculated V. riparia and 110R indicators. At least one virus-tested candidate clone of 19 different grapevine varieties were identified, that could represent a potential primary source for a grapevine certification program in Kosovo.