Injurious and beneficial mites on urban trees in northern Italy

The studies carried out on urban public green in some cities in northern Italy have allowed the identification of a rather complex acarofauna, on the whole made of 24 species. Most of these mites are phytophagous (14 species) made up exclusively by Prostigmata and dominated by Tetranychidae, with the presence of Tenuipalpidae and Eriophyidae of secondary importance. Among the predators both Prostigmata Cheyletidae and Mesostigmata Phytoseiidae were found. The latter are by far the most important antagonists. Both groups are made up mostly by native species, mainly widespread on the crops and on natural vegetation. Only some, Oligonychus bicolor (Banks), Anthocoptes punctidorsa (K.), Coptophylla lamimani (K.), Tegolophus califraxini (K.), Typhloctonus squamiger (Wain.) are foreign species and most probably come from their native area nurseries. The analysis of the three kinds of green in the cities - trees along roads, urban parks and woody areas in the suburbs - does not highlight a great difference in the acarofauna of the first two categories while it is less diversified and less numerous in the woods. This situation can be attributed to the heterogeneous origin of the species that colonise the kinds of green that are mainly found in cities, whereby those imported are added to the native ones. Phytoseiidae have confirmed their role as predators of the protection type, being present on many trees where no phytophagous species were found. This allows them to prevent the outbreaks of harmful mites also in the urban environment. In fact they are extremely rare in the urban areas where, thanks to a careful pest management, these predators have been able to assert themselves.