the president's address. 61 



Brown Rot of Fruit. 

 (Sclerot in ia fruct igena. ) 



This is undoubtedly one of the worst of fungus diseases with 

 which the fruit-grower has to contend, and unfortunately it 

 is always present in more or less quantity wherever fruit is 

 grown. It attacks apple, pear, plum, cherry, and, in fact, all 

 orchard fruits, and is also common on many wild plants 

 belonging to the order Rosaceae. 



The young leav 7 es are first attacked, the fungus appearing 

 on the surface in the form of small, minute, velvety olive- 

 brown patches, which gradually increase in size and grow into 

 each other, until eventually the greater portion of the leaf 

 becomes covered. The spores are carried by rain, wind, insects, 

 etc., from one leaf to another, and at a later stage also on to 

 the young fruit. 



On the latter the first evidence of disease is the presence 

 of small brown spots on the surface of the fruit. These spots 

 gradually increase in size, and at a later stage become studded 

 with small whitish downy warts, which constitute the conidial 

 or summer form of fruit, at one time called Monilia fructigeita, 

 before it was discovered to be only one stage in the life-cycle 

 of the higher form of fungus called Sclerotinia fructigena. 



On the apple the white conidial tufts are arranged in con- 

 centric circles, being, in fact, miniature fairy-rings, due to 

 gradual extension of the fungus on every side from the point 

 of infection. On other fruits the tufts are irregularly scattered, 

 and not arranged in circles. 



Diseased apples do not rot, but shrivel, and remain in a dry, 

 mummified condition throughout the winter, either hanging on 

 the tree or lying on the ground. The following spring, just 

 when the young leaves are expanding, these mummified apples 

 produce another crop of conidia, which are dispersed by various 

 agents, and infection of the young leaves results. 



