Abstract
Quantitative estimates of vector populations and their infectivity in the wild and in cultivated compartments of agroecosystems have been carried out to elucidate the role of the wild compartment in the epidemiology of Flavescence dorée (FD). Seven sites were selected for the investigations in the Piedmont Region of Italy. They were characterized by a high variety of agricultural and ecological landscape features, and included a vineyard surrounded by wild vegetation. In order to describe abundance and prevalence of FD-infected vectors in the cultivated and wild compartments of the vineyard agroecosystem, adults of Scaphoideus titanus were collected by yellow sticky traps inside and outside the vineyard over the period July 10th–September 9th, 2015. They were counted and singly analyzed for the presence of FD phytoplasmas by PCR. Multifactorial correlations among vector population level, prevalence of infected insects inside and outside the vineyards, disease prevalence in cultivated and wild Vitis plants, and location of wild Vitis plants with respect to the vineyard were analyzed. Abundance of S. titanus adults significantly decreased from the end of July onwards, particularly inside the vineyard (average range 22.7 ± 2.5 insects/trap). Percentage of FD-positive S. titanus was significantly higher outside the vineyard (up to 48% on average) compared to inside the vineyard (up to 34% on average), and increased during the season in both compartments.
Highlights
Flavescence dorée of grapevine (FD) is a phytoplasma-associated disease present in severalEuropean countries
We demonstrated that infected vines have low FD phytoplasmas (FDp) load early in the season [32] and that acquisition of FDp by S. titanus correlates with phytoplasma load in the plant [33]
High numbers of S. titanus adults were collected from the wild vegetation compartment of several sites, and vector population levels of this compartment were higher than those measured inside the corresponding vineyard
Summary
Flavescence dorée of grapevine (FD) is a phytoplasma-associated disease present in several. The disease has a major impact on viticulture because inflorescences and berries dry up, shrivel, and cannot be further processed. Plants can either be persistently infected over several years and eventually die or recover [3,4]. Phytoplasmas are phloem-obligate, nonculturable pathogens described under the provisional genus “Candidatus Phytoplasma” mainly based on 16S rRNA gene phylogeny. FD phytoplasmas (FDp) are those belonging to the 16SrV-C and -D ribosomal subgroups transmitted by the American grapevine leafhopper, Scaphoideus titanus Ball [1,5]. The vector transmits FDp according to a persistent propagative modality; Insects 2020, 11, 301; doi:10.3390/insects11050301 www.mdpi.com/journal/insects
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