Abstract: The many years’ study on species composition and harmfulness of aphids infesting perennials in the decorative plant collection Agricultural University in Poznań permited to ascertain occurrence of 23 aphid species on 66 species of decoratice perennials, representing 20 botanical families. The species that occurred in all the four study seasons in 2000, 2002, 2003 and 2005 included: Aphis fabae Scop., Brachycaudus cardui (L.) and Aphis sedi Kalt.. Very often Aphis newtoni Theob., Acyrthosiphon malvae (Mosl.), Brachycaudus helichrysi Kalt. and Longicaudus trirhodus (Walk.) were found. Spring and early summer was the period of numerous occurrence of aphids on decorative perennials. The high degree of plant infestation was resulted in decreasing the plant’ decorative value. The aphid infestation may be especially dangerous for numerous cultivars of Dahlia x cultorum, Eryngium planum, Echinops ritro, Leucanthemum maximum, Papaver orientale, Sedum aizoon, Iris sibirica, Yucca filamentosa, Achillea ptarnica, Dicentra eximia, Doronicum orientale i Geum coccineum.

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