A BLOSSOM WILT and CANKER OF APPLE TREES.

Abstract

Summary. 1 A “Blossom Wilt and Canker” of apple trees, produced by a species of Monilia, is causing great loss to fruit growers in the southeast of England. 2 Infection takes place through the open flowers; the fungus invades the tissues of the flowering spur, thus killing the inflorescence and the leaves of the spur; the disease may reach the branch and produce a canker. 3 Spurs killed during the summer, together with the accompanying cankers, produce pustules of conidia during the following winter and spring; these conidia, falling on the flowers as they open, give rise to a new outbreak of the blossom-wilt disease. 4 When a canker has shed its crop of conidia it becomes covered with callus which eventually heals the lesion. 5 Inoculation of apple flowers with conidia from pure cultures of the fungus resulted in the death of the inflorescences and the spurs; in some cases cankers were produced. Conidia-bearing pustules of the organism appeared on these dead spurs and cankers during the following winter. 6 The causal organism is a grey Monilia easily distinguished from M. fructigena; at present it is to be referred to Monilia cinerea Bon. 7 On culture media the habit of the fungus is different from that of the grey Monilia (also referred to M. cinerea by American workers) which is commonly found in North America. 8 The, disease may be kept in check by cutting out all dead spurs and cankers before the flowers open; on the first appearance of the disease all wilted trusses and dead spurs should be promptly removed. Spraying operations can be efficacious only when they kill the conidial pustules or prevent them from shedding their conidia during the flowering period.