Phytoseiid mites (Acari: Phytoseiidae) on apple tree and spontaneous flora under different environmental and cultural conditions in Valtellina (Lombardy, Northern Italy)

Abstract

In the years 1999 and 2000 a research to evaluate the presence of Phytoseiid mites on apple and spontaneous flora under different environmental and cultural conditions was carried out in Valtellina, the main Lombard area for apple cultivations. 18 apple orchards were chosen belonging to three different types: abandoned, in marginal areas and in mono-cultural areas. On the whole 6 species of Phytoseiid mites were found but only three have played an important role: Amblyseius andersoni (Chant), Typhlodromus pyri Scheuten and Euseius finlandicus (Oud.). The presence of Phytoseiid mites on different orchard types is influenced more on the qualitative than quantitative plan. The densities have not shown any notable differences on the cultivation, being approximately 0.5 specimens per dm2 of the leaf area, and there has been a modest increase on natural vegetation in the abandoned orchards. Phytoseiid mites are always present on apple trees and with permanent populations. On spontaneous flora the situation is variable in relation to the the host species. Phytoseiid mites are much more abundant on cherry, ash and elder trees rather than on apple trees. A. andersoni and T. pyri are the dominant species on the crop. The former is mostly found on mono-cultural areas while the latter in marginal areas but in uncultivated areas E. finlandicus coming from spontaneous flora predominates. E. finlandicus is the prevalent species on wild vegetation but in mono-cultural areas A. andersoni and T. pyri are important too. In the agro-ecosystem there is a double flow of Phytoseiid mites, from and to the cultivation. The critical factor that determines the direction of this move is the volume of the bio-mass. In marginal areas spontaneous essences predominate, with movements towards the apple tree, in monocultural areas there is an inverse movement.