22 



bodies. The spores fall apart readily and are scattered by the 

 wind or carried by insects to other apples. If they gain access 

 to the flesh of an apple through a, cut or rupture of the skin 

 they germinate, producing fungal threads (mycelium) which 

 develop within the tissues of the apple and cause the charac- 

 teristic " brown rot." The rot extends very rapidly and within 

 a week or ten days the' fruit will be destroyed. 



When a diseased apple is in contact with others on the 

 tree, the latter may become infected by contagion; frequently 

 a bunch of apples is found which shows fruit with the rot in 

 various stages of development. Fig. 1 is a photograph of such 

 a cluster of apples obtained in late summer from a tree of 

 Warner's King. The disease had commenced in the small 

 withered apple (a); below this and in contact with it is another 

 apple (b) which had evidently been affected for some time as it 

 is much shrunken and wrinkled. The rot had extended from 

 this apple to the one on the left (c), which, at the time the 

 photograph was taken, was permeated with the fungus and bore 

 numerous powdery pustules; but it was only very slightly 

 shrunken and its surface showed but little wrinkling. On the 

 right is an apple which is still quite sound. 



Mummied Apples and Methods of Overwintering. Those 

 diseased apples which become attached to the tree usually 

 remain in that position throughout the winter, becoming dry 

 and shrivelled, and they constitute the so-called " mummied 

 fruits (Fig. 2). Many of the spores on the pustules of these 

 " mummies " are washed away by rain in winter or dispersed 

 by the wind; others remain on the pustules but usually lose 

 their power of germination. As summer approaches, however, 

 the ' ' mummies ' ' produce a new crop of spores and cause 

 infection of the young fruit. A ' ' mummy ' ' frequently infects 

 the growing apples through direct contact, but in any case 

 apples in the neighbourhood of a " mummy " are liable to 

 spore-infection and such newly-infected fruit will soon produce 

 myriads of spores which serve to spread the disease. The 

 spores are very minute in size and are easily dispersed by 

 wind. Insects, too, crawling over the fruit, may not only carry 

 the spores from one apple to another, but, in the case of biting 

 insects, such as wasps, produce wounds which enable the spores 

 to reach the exposed flesh of the apple, where they develop 

 mycelium and reproduce the rot. 



Spur Canker. On some soft-wooded varieties of apples 

 (e.g., Lord Derby and James Grieve) the disease may extend 

 along the stalk of the affected fruit into the fruiting spur; or 

 even as far as the branch itself, producing in the latter a 

 canker round the base of the spur. In this capacity of form- 

 ing cankers the fungus resembles the " Blossom- Wilt " fungus 

 (see Leaflet No. 312). 5The two diseases are, however, quite 



