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Published online by Cambridge University Press: 18 September 2024
In 2014, Amblyseius andersoni (Acari: Phytoseiidae), was newly discovered in apple (Rosacaea) orchards in central Japan. In 2022, I found A. andersoni on leaves in an apple orchard in northern Japan. Amblyseius andersoni had been not observed in the orchard until at least 2018; only Neoseiulus womersleyi and Typhlodromus vulgaris (Mesostigmata: Phytoseiidae), both of which are native to Japan, had been observed on apple leaves. To understand the impact of A. andersoni on the two phytoseiid mite species, I compared the seasonal occurrences of the phytoseiid species and of Tetranychus urticae (Trombidiformes: Tetranychidae) in the orchard in 2018 and 2022. In both years, T. urticae numbers increased from mid-July to early August and then rapidly decreased with increasing N. womersleyi numbers. Mean total occurrence numbers of N. womersleyi and of T. urticae did not differ significantly between the two years. Amblyseius andersoni occurrence therefore likely had little impact on seasonal N. womersleyi occurrence. In contrast, in 2018, many T. vulgaris individuals were observed from August onwards, when T. urticae numbers had decreased, but T. vulgaris was seldom observed in 2022, although many A. andersoni were, suggesting that A. andersoni likely displaced T. vulgaris in the apple orchard.
Subject editor: Elizabeth Long