S14 - Session P4 - Dispersal of Neophysopella tropicalis in vineyards with plastic cover

Authors: Lilian Amorim *, Ana Simes, Pamela Dutra

Plastic covering has been adopted in vineyards for table grape in Brazil. This technique is very efficient in controlling grapevine downy mildew ( Plasmopara viticola ) and anthracnose ( Sphaceloma ampelinum ), as it reduces the leaf wetness period. However, plastic covering shows little effect on the incidence of grapevine rust caused by Neophysopella tropicalis . The objective of this work was to analyze the temporal dynamics of airborne N. tropicalis urediniospores in an experimental field of grapevines with and without plastic cover. Six passive impactor spore traps, with glass slides covered by double-sided self-adhesive tape, were installed in the plots with and without plastic cover. The amount of single as well as clusters of N. tropicalis urediniospores was quantified weekly at a light microscope. The urediniospores that germinated on the slides were also quantified. Meteorological data were collected daily and correlated to the amount of urediniospores. There was a greater number of urediniospores in traps placed in plots with plastic cover (average of 920 urediniospores/slide) than in those without plastic cover (average of 748 spores/slide). On the other hand, the amount of germinated urediniospores was five times greater in spore traps located in plots without plastic cover than in plots with plastic cover. Regardless of treatment, most urediniospores were in clumps. The number of urediniospores collected in the plots without plastic cover was positively correlated with the maximum wind speed (m/h) and the daily wetness period (h) ( p ≤ 0.05). The amount of germinated urediniospores also showed a significant correlation with the wetness period ( R = 0.55). The number of hours with relative humidity greater than 90% showed a positive correlation with the number of germinated spores, regardless of the treatment ( R > 0.45). The plastic covering over the grapevines concentrates the spores at canopy level but limits the germination of N. tropicalis urediniospores.