Comparison of two control strategies of Panonychus ulmi (Koch) on vineyards

Two control strategies of Panonychus ulmi (Koch) on vine were compared for two years. A threshold of 10 mites per leaf is adopted following the first method (Girolami, 1981). Vineyards are sprayed when the percentage of leaves infested by one or more mites is higher than 30–45 % in summer (60–70 % in spring) following the second method (Baillod et al., 1979). Research was carried out in vineyards in the Veneto region heavily infested by P.ulmi . Five miticide treatments were applied in 1983 and 7 in 1984, in the plots where the percentage of infested leaves method was used. When the threshold level of 10 mites per leaf was used, 1 spray was applied in 1983 and 2 in 1984. Following the first strategy, vineyards are sprayed at low density levels (maximum 1–4 mites per leaf), therefore prematurely; these treatments prevent the possible increase of predacious mites and insects; a delayed increase of phytophagous mite population is not prevented in favourable climatic conditions. The threshold level of 10 mites per leaf allows, in many cases, the arrival of winged predators, mostly Anthocoridae , ( Orius vicinus Ribaut) and an increase in population of predacious mites ( Phytoseiidae and Stigmaeidae ); Tetranychid mites are controlled without damages and a low number of treatments are required.