Effect of grapevine varieties on phytoseiid (ACARI) populations in the northwestern area of Portugal

Abstract The occurrence of phytophagous mites such as Panonychus ulmi may be influenced by leaf morphology, with different behaviors according to the vine varieties, and little is known on the preference of predators of the family Phytoseiidae. The aim of this study was to evaluate the abundance of Phytoseiid species on different white and red grape varieties according to morphological leaf characteristics and sampling sites. Samplings were conducted between July and September 2017 in the northwestern region of Portugal in the Subregion of Lima at three sites: Escola Superior Agraria (ESA), Estacao Vitivinicola Amândio Galhano (EVAG), and Casa de Barreiros (CBAR). Five white grape varieties and five red varieties were sampled at each site, where 50 leaves/grapevine were collected. A total of 7301 mites were sampled, belonging to seven species. The most abundant species were Typhlodromus (Typhlodromus) pyri (95%), Typhlodromus (Typhlodromus) exhilaratus (3.3%) and Amblyseius andersoni (1,4%). The site with the highest abundance was ESA (57%), followed by EVAG (30%) and CBAR (13%). In this study there were significant differences in mite density in most varieties when they were compared between sampling sites. However, some phytoseiid species were influenced by leaf pilosity. Typhlodromus. (T.) pyri preferred leaves with more trichomes, cottony, while A. andersoni and T. (T.) exhilaratus with fewer trichomes or glabrous. The influence of cultivar leaf pilosity on the abundance of phytoseiid species can be an important factor for effective biological control in the field, since this influence can be used in decision making for control of phytophagous mites.