38 



during the flowering period. The former retards the develop- 

 ment oi the flowers, and causes them to remain susceptible 

 to infection for a longer period than usual, and the latter 

 favours the production (by means of the pustules on mummied 

 fruit and dead wood), of an abundance of spores. 



Wituer-Tip. In Wither-Tip the fungus attacks the young 

 green shoots and causes them to die-back. In this way many 

 of the leading shoots are killed (Fig. 4), the buds at the base are 

 then stimulated' to precocious development, and instead of 

 fruit buds, a number of weak, ill-ripened shoots are produced. 



The Wither- Tip form arises from spores formed on the 

 pustules on mummies, on wood attacked the previous season, 

 and probably also from flowers killed by Blossom- Wilt. It 

 usually commences about 'the end of April or the beginning of 

 May, when some of the young shoots may be seen to wither. 

 The wilt does not always begin at the tip of the shoot; it may 

 commence some distance down, the fungus in this case entering 

 at a node or through a leaf. Shoots attacked by Wither-Tip 

 hang downwards; at first they are flaccid, but later the tissues 

 harden and dry, and the dead shoots may be recognised by the 

 characteristic curve. The dead brown leaves, being killed pre- 

 maturely, do not usually fall from the tree, but hang on during 

 winter and even until spring (Fig. 4). When it is a spur that 

 is invaded the fungus sometimes forms a canker similar to that 

 formed in apples. 



Spore-pustules develop during the following winter and 

 spring, on all the shoots and spurs which have been killed 

 (Fig. 4, see specimen to left, lower part), and these give off 

 spores which provide for the fresh infection in spring. The 

 pustules are small and grey in colour, they commence to show 

 in December, and increase in number as spring advances. 

 Large quantities o>f spores are liberated in March, April and 

 May. The fungus in dead twigs may retain its vitality for 

 more than one season and liberate a crop of spores during the. 

 second winter after attack. The importance, therefore, of 

 removing such shoots is obvious. 



As is the case with Blossom- Wilt, the severity of Wither-Tip 

 is greater in some seasons than in others. Wet, cold weather 

 in spring favours its development, but since epidemics of 

 Wither-Tip have been found to correspond with severe attacks 

 of aphis, it is possible there may Be a connection between them. 

 The aphides, by puncturing the leaves, would injure the 

 tissues, and render them particularly susceptible to invasion 

 by the fungus mycelium. 



Brown Rot on Fruit. The fruit is most often attacked 

 when approaching maturity, the slightest wound or bruise 

 allowing the spores to bring about infection. Once it has gained 

 an entrance the mycelium rapidly destroys the fruit, and finally 

 reduces it to the hard, wrinkled structure known as a 

 " mummy." The mummies may fall to the ground, -but usually 



