Atmospheric spore content of the grapevine pathogenic fungi Plasmopara viticola and Botrytis cinerea in Mediterranean vineyards

Grapevine (Vitis vinifera L.) cultivation is one of the oldest, most widespread and important crops in the world. Downy mildew and grey mould are fungal diseases caused by the oomycete Plasmopara viticola and the ascomycete Botrytis cinerea, respectively. These diseases have a serious negative impact on viticulture, reducing the quantity and quality of harvests. Monitoring of variables affecting the environment-host-pathogen system in important viticulture areas is necessary for the control and prevention of these diseases. The aim of this study was to analyse the dynamics and behaviour of the atmospheric content of P. viticola and B. cinerea spores, as well as their relationship with different meteorological variables and the phenology of the grapevine.

The study was conducted between May and November 2023 in a vineyard belonging to the land of the Designation of Origin Uclés, D.O Uclés, located in the west of Cuenca province (Castilla-La Mancha region, central Spain). The area has a dry Mediterranean climate. Aerobiological sampling was carried out using a Hirst volumetric spore trap placed 2 metres above the ground in a vineyard of the Syrah grape cultivar. Samples were prepared and analysed following the methodology established by the Spanish Aerobiology Network. Phenological sampling was carried out weekly on 20 Syrah grapevines close to the spore trap, using an adaptation of the BBCH scale. Meteorological data were obtained from the Spanish Meteorological Agency (AEMET). The relationship between spore concentrations and meteorological variables was analysed using Spearman's non-parametric correlation test and Principal Component Analysis (PCA). Furthermore, an intradiurnal analysis of spore concentration was carried out.

A total of 894 spores/m³ of B. cinerea and 758 spores/m³ of P. viticola were obtained during the studied period. For B. cinerea, the daily peak spore concentration was on 18 October with 54 spores/m³, for P. viticola it was on 13 November with 74 spores/m³. The phenological stages with the highest daily spore concentrations for both pathogens were flowering, ripening and senescence of the grapevine. The spore concentration of both pathogens is positively influenced by relative humidity (RH), while temperature variables (mean, maximum and minimum) have a negative influence. Intradiurnal analysis showed that the highest spore concentrations occurred between midday (11:00-12:00) and early afternoon (16:00-17:00).

Flowering and ripening are critical stages for the development of these diseases. High temperatures and drought, characteristic of the summer period in areas with a dry Mediterranean climate, inhibit sporulation. However, diseases can develop before and after this period, when conditions are favourable. Progress in the knowledge of the environment-host-pathogen system in these areas will help to decide the most appropriate times for the application of phytosanitary treatments.

This work has been funded by the Ministry of Education, Culture and Sports of the JCCM, through the project SBPLY/21/180501/000172 and by the University of Castilla-La Mancha (UCLM) through the project 2022-GRIN-34507 and a pre-doctoral contract to Guillermo Muñoz-Gómez of the “Plan Propio I+D+I” of the UCLM.