Species of Armillaria in southern England

Isolates of Armillaria obtained from a wide variety of material were identified by means of the mating test devised by korhonen and by their growth on various media. Pathogenicity was tested by inoculating small pines. Five species were found, of which Armillaria mellea (Vahl ex Fr.) Kummer and A, ostoyae (Romagn.) Herink were highly pathogenic: the former killed a wide variety of broadleaved trees and conifers whilst the latter killed fewer species, mainly conifers. A. bulbosa [Armillariella bulbosa (Barla) Romagn.] was much less pathogenic and was found in trees weakened by suppression or in other ways;it also caused extensive butt‐rot in some broad‐leaved trees. A. tabescens (Scop, ex Fr.) Emel, was less common and occurred in stumps of broadleaved trees: it was virtually non‐pathogenic. A species provisionally designated B by Korhonen was discovered only once. Brief accounts are given of these species with respect to rhizomorph behaviour and factors affecting their occurrence in woodland and gardens.