Pollen availability and abundance of predatory phytoseiid mites on natural and secondary hedgerows

Mites occurring on a number of natural and secondary (i.e., planted) hedgerows located in north-eastern Italy were monitored with particular attention being paid to phytoseiids (Acari: Phytoseiidae). Pollen diversity and abundance were analysed to highlight potential relationships between pollen availability and phytoseiids. Secondary hedgerows were structured in modules containing a single species (field maple, hornbeam, dogwood, hazel, and elderberry) and modules containing a mixture of the above-mentioned species. These hedgerows were located in an experimental farm where they were contiguous to a vineyard. Natural hedgerows were located in the same area. The pollen of Poaceae was the most important component of non-arboreal pollen (NAP), and that of elderberry of arboreal pollen (AP). Pollen diversity was higher on natural than on secondary hedgerows. Generally, pollen densities reached relatively high levels from late April to late June and decreased in summer. Pollen was more abundant on natural than on secondary hedgerows and phytoseiid abundance showed a similar trend. On elderberry and hornbeam in natural hedgerows a potential relationship between pollen availability and the abundance of phytoseiids, in particular of Euseius finlandicus (Oudemans) was found. Experimental pollen applications increased the fecundity and the abundance of this species.