86 



Commercial Gardening 



Brown Fruit Rot (Sclerotinia fructigena). This is undoubtedly the 

 commonest and most generally distributed of diseases attacking plants 

 belonging to the family Rosaces, to which the majority of our orchard 

 fruit trees belong. Until recently the injury was supposed to be entirely 

 due to a fungus called Monilia fructigena. It has, however, now been 

 proved that the Monilia is only one phase in the life-cycle of a more 

 highly organized fungus called Sclerotinia. It is quite true that the 

 Monilia condition causes all the damage, yet it is well to know that 

 another stage exists, which under certain conditions is capable of tiding 

 the parasite over from one year to another. 



As usual, the effect on the fruit is best known to people generally, 

 appealing as it does both to the eye and the pocket. On apples the earliest 

 indication of its presence is the appearance of one or more small, brown 



patches which gradually increase 

 in size, until in many instances 

 the entire surface of the fruit 

 becomes diseased. Soon after- 

 wards whitish warts, arranged 

 in concentric circles, resembling 

 little fairy rings, burst through 

 the skin covering the diseased 

 parts. These warts are the 

 summer fruits, or Monilia con- 

 dition of the fungus. If a thin 

 slice of one of these white warts 

 is examined under a microscope, 



it will be seen to consist of numerous spores arranged in long chains, like 

 strings of beads. These spores become free from each other when ripe, 

 and are scattered by wind, &c., and are capable of infecting other fruits 

 or young shoots. Such diseased apples do not rot and decay soon, but 

 become dry and mummified, and often remain hanging on the tree until 

 the following season (fig. 348). 



Whether hanging on the tree or lying on the ground, such diseased 

 apples produce a second crop of Monilia spores the following spring, each 

 one of which is capable of infecting any leaf, shoot, or fruit on which it 

 may alight. It sometimes happens that apples infected with this disease 

 turn almost black all over, and are popularly known as " Black Apples ". 

 These become dry and hard, and do not produce Monilia spores until the 

 spring. 



When plums and cherries are attacked, the white warts of Monilia 

 fruit are not usually produced in irregular circles as on the apple, but are 

 irregularly scattered over the fruit. When diseased fruit has been lying 

 on the ground for two seasons, and has become more or less buried, it 

 sometimes produces the higher or Sclerotinia kind of winter fruit, under 

 the form of little brown cups supported on slender stalks. The spores of 

 this form are, of course, also able to set up an infection. 



A B 



Fig. 348. Brown Fruit Rot 

 A, Apple in mummified condition. B, Chains of spores. 



