Drupaceous Fruits 81 



flower to wither and eventually fall off as a rotten mass, 

 carrying contagion to everything in its path. This damage 

 to the flower is often confounded with frost effects. From 

 the flower the rot may spread to adjacent twigs, through 

 the flower stalk. Smith states that the examination of hun- 

 dreds of twigs in all stages of disease showed that every one 

 was associated with lilighted and persistent flowers. Infec- 

 tion of the twigs may also occur directly from diseased fruit. 

 Even large branches may become seriously cankered. From 

 repeated observations, however, it seems probable that 

 branches cannot be infected except through wounds. 



The inroads of this disease are so serious that many peach 

 and plum growers have been obliged either to secure a 

 remedy for this pest or abandon the crop. Years in which 

 there is full fruitage, accompanied by damp, warm weather, 

 are almost certain to bring a severe attack. But it is not the 

 weather which directly causes the rot; rather it is the rapid 

 development of the fungus under proper weather conditions. 



The mummified fruits and cankers serve as the hibernating 

 quarters of the causal fungus. If these mummies be carefully 

 observed in the spring, some of them will be seen to bear 

 small stalked disks (Fig. 41). These are the organs which 

 furnish spores for the spring infection. 



It follows that any practice which destroys the mummified 

 fruits lessens the risk of infection as does also the pruning 

 out of cankers. Observations by Pollock, ^^^ extended over a 

 period from 1909 to 1918, show that the sclerotia of the 

 causal fungus may remain alive for at least ten years, and 

 some of them produce ascocarps every year; old mummies 

 or fragments of mummies giving rise to smaller spore- 

 bearing structures than those formed from younger sclerotia. 

 In the light of these observations attesting to the long life 

 of the sclerotia, the plowing under of diseased fruits, here- 

 tofore advised, cannot be regarded as a good practice. Ac- 

 tive treatment in the form of spraying is necessary. The most 

 successful spray is that employed by Scott, which gave the 

 following results : — 



