Rare and endangered species of Aphyllophorales have been studied on Quercus robur in Lithuania. In total, 5455 trees and 742 stumps of oaks have been investigated in pure oak stands, mixed deciduous woods, mixed coniferous–deciduous woods, parks, and in open landscapes. Fungi in the herbarium BILAS (Vilnius) were examined.

The ecology, distribution, and status of the following polypores are treated, viz Fistulina hepatica (Schaeff.: Fr.) With., Grifola frondosa (Dicks.: Fr) S.F.Gray, Hapalopilus croceus (Pers.: Fr.) Bond. & Sing, Inocutis dryophila (Berk) Fiasson & Niemelä, Inonotus dryadeus (Pers.: Fr.) Murr., Piptoporus quercinus (Fr.) Pilát, and Polyporus umbellatus (Pers.) ex Fr. Each species is briefly described and localities are listed in detail. All species, except F. hepatica and P. quercinus, are included in the Lithuanian Red List of fungi. We suggest these two species should be added to the list, and classified according to the IUCN categories Near Threatened (NT) and Endangered (EN), respectively.

The importance of saving the right type of substrate and habitat for the actual species is stressed. Thick dead, standing or fallen trees, and old stumps should not be removed, as F. hepatica, G. frondosa, H. croceus, and P. quercinus may continue to fructify for many years on this type of wood. Suppression of old host trees, formerly growing in a more open environment, is a problem at many sites. A proper clearing around these oaks is necessary to keep the oaks alive as long as possible. The necessity of favouring younger oaks of different age classes in the stands is pointed out, as a continuous supply of thick host trees is needed to preserve the fungi.

Hapalopilus croceus, one of Europe’s most endangered fungi, fructifies on old thick oaks, a substrate that becomes more and more rare. All Lithuanian host trees of H. croceus are proposed to be preserved (even when dead) together with a sufficient number of oaks in the surroundings. In Sweden, which is still one of the strongholds of H. croceus in Europe, the species is classified as Critically Endangered (CR) and since 2000 also protected.

The following two oak sites in Lithuania are highly recommended to be preserved, more closely investigated, and managed for the future: Punios Šilas (squares 31, 32 & 38), Alytus district. In this very valuable locality, where many old and thick oaks are suppressed by surrounding younger trees, we found H. croceus (on 11 oaks), I. dryophila, F. hepatica, P. quercinus, and the red-listed beetle Osmoderma eremita (Scop.). “Kauno Ažuolynas” in Kaunas is a unique park with more than 800 mostly old, thick oaks, mixed with, e.g., Tilia. Here we observed F. hepatica, G. frondosa (on 11 oaks), H. croceus (on 8 oaks), and I. dryophila.