PEACH BROWN-ROT. 11 



peaches may be readily sold at good prices 15 or 20 cars of fruit 

 specked with brown-rot are sufficient to create a "glut" and often 

 bring scarcely enough to pay expenses. 



NATURE OF THE DISEASE AND THE FUNGUS CAUSING IT. 



Brown-rot is a fungous disease which affects the fruit of the peach, 

 causing it to decay on the trees or en route to market. As already 

 stated, it is caused by a fungus whose botanical name is Sclerotinia 

 fructigena (P.) Schrot. Many fruit growers call it Monilia, the name 

 given to the summer stage of the fungus before the perfect form was 

 known. The fungus also attacks the blossoms and twigs, thus often 

 destroying a portion of the fruit crops at blooming time. The dis- 

 eased blossoms turn brown and become dried, adhering to the twigs 

 for some weeks. The fungus may extend from the dead blossom into 

 the bark, forming a small brown canker which frequently girdles the 

 twig. In low, damp situations, especially in a wet spring, many 

 blossoms and fruit-bearing twigs may thus be destroyed. Some of 

 the green fruits may become affected at any time during the season, 

 and even young peaches half an inch or less in diameter may rot, but 

 as a rule no serious outbreak occurs until the fruit is nearing maturity. 

 It is at harvest time ordinarily that the greatest destruction is 

 wrought. 



On the fruit, brown-rot may at first be observed as a small circular 

 brown spot, which under favorable conditions rapidly enlarges, until 

 within two or three days the entire peach goes down in decay. While 

 the spot is yet small, whitish tufts of spore-bearing threads begin to 

 appear. As the spot enlarges, these tufts, arranged more or less in 

 concentric rings, become so numerous as nearly to cover the surface, 

 giving the diseased area a grayish, moldy appearance. (See PI. I.) 

 Most of the rotten fruit drops to the ground, but a considerable por- 

 tion of it may shrivel up on the tree and remain attached until the 

 following season. As in the case of diseased blossoms, the fungus 

 may extend from the rotting peaches into the twigs, killing them and 

 thus reducing the prospects of a crop the following year. In a wet 

 season some varieties suffer so badly from twig infections that the 

 trees have the appearance of a pear tree attacked b} T blight. 



The fungus passes the winter in the mummified peaches hanging 

 on the trees, as well as in those that have fallen to the ground. 

 During the spring and summer, especially in wet weather, the fungus 

 in these mummies produces large crops of summer spores for the 

 infection of the new fruit crop. In the mummies on the ground the 

 fungus forms a black leathery sclerotium, which is the foundation of 

 another kind of spore production. In the spring, during the blooming 

 period, small, brown cup-shaped bodies (apothecia), resembling toad- 



174 



