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.     

SOME FURTHER OBSERVATIONS ON FOMES ANNOSUS FR.

In a wide range of British forests Fomes annosus attacks originatefrom stump infection following thinning and under suitable conditionsa relation can be found by sampling between the number of treeskilled and the proportion of stumps earlier infected. In EastAngliavery dry weather apparently favours stump infection, whichotherwise often reaches a maximum in late winter. There is ageneral tendency for stump infection to increase. In ThetfordChase attacks on many acid soils have become stabilized, whereasthose on some alkaline soils are still progressing. Recent estimatesof economic loss through killing and butt-rot are compared.Experiments show that stump treatment gives excellent protectionagainst killing, and the present large-scale creosoting of stumpsin East Anglia is also effective. An outline is given of recentresearch on stump treatments.