Diversity and abundance of Phytoseiidae (Acari: Mesostigmata) on horse chestnut (Aesculus hippocastanum L.) in an urban environment: a comparison between Greece and the Czech Republic

Horse chestnut, Aesculus hippocastanum L. (Sapindaceae), is a large deciduous tree native to a small area in the Pindus Mountain mixed forests and the Balkan mixed forests of Southeast Europe. It was introduced to most countries in Europe mainly for ornamental purposes. The aim of the present study was to assess the occurrence, species composition and population densities of phytoseiid mites on A. hippocastanum in countries where this tree species is autochthonous and to compare them with Central Europe. In addition, we tested whether the horse chestnut leaf miner, Cameraria ohridella or the horse chestnut leaf blotch, Guignardia aesculi has any effect on Phytoseiidae population density. Leaf samples were collected in the cities of Ceske Budějovice, Czech Republic and Orestiada, Greece in September 2013 and 2015, respectively. Thirty compound leaves were randomly taken from tree branches up to 2.5 m above ground in both localities. Mites were collected by washing the leaves in ethanol and were then mounted in lactic acid and identified. A total of 441 specimens of phytoseiid mites belonging to six species (Euseius finlandicus, Neoseiulella tiliarum, Kampimodromus aberrans, Paraseiulus talbii, Phytoseius macropilis and Typhlodromus (Typhlodromus) pyri) were collected. A significantly higher population density of Phytoseiidae was found in Ceske Budějovice. The density was not affected by the horse chestnut leaf miner, Cameraria ohridella or the horse chestnut leaf blotch, Guignardia aesculi. Euseius finlandicus was the predominant species in both Ceske Budějovice (96.8%) and Orestiada (48.4%) where, however, it competed with K. aberrans (42.9%).