38 THE BITTER ROT OF APPLES. 



examined in the spring many of these mummified fruits are found to 

 contain spores of the bitter-rot fungus in quantity. Inoculations made 

 by us with such spores have shown them to be fully capable of remain- 

 ing alive over winter and of producing the disease in July and August 

 of the following year. 



It was formerly supposed that the fungus passed the winter in the 

 mummies, but as most of these were on the ground it was difficult to 

 understand how the apples high up in the trees became infected. It 

 now seems probable that the mummies play a comparatively small 

 part in serving as distributing points for spores from year to year. 



After the fungus becomes started on a number of fruits it spreads 

 to neighboring apples and trees with great rapidity. The sticky 

 nature of the spore masses precludes any theory of wind distribution. 

 The spores are never dustlike, so that they could be blown about, but 

 are generally stuck together, forming a sticky, paste-like mass. Rain 

 and dew play an important part in distributing the spores. 



Numerous small insects which frequent apple trees in the late sum- 

 mer, such as members of the genus Drosophila. probably carry the 

 bitter-rot spores from one tree to another. Clinton (1902) proved 

 that this was actually the case by placing some of these flies on sound 

 apples and thereby producing the disease. 



REMEDIAL MEASURES. 



Although the bitter rot has been so destructive to apple crops for thirty 

 years or more, little if any headway had been made until recently 

 toward combating it successfully. The disease may still be regarded 

 as one of the most difficult ones to control, although it now seems 

 probable that greater success ought to attend preventive measures. 

 These may now be placed under these heads: 



1. Removal of diseased fruits and mummies. 



2. Removal of limb cankers. 



3. Spraying with fungicides. 



REMOVAL OF DISEASED FRUITS AXD MUMMIES. 



Apples affected with bitter rot generally fall from the trees during 

 the later stages of the disease. In main' cases the spores in these rotted 

 apples will live through the winter, and may be carried to sound 

 fruits the following season. Such apples as do not fall dry up and 

 hang on the trees all winter in a mummiiied condition. The next 

 3^ear the spores formed in these mummies may infect sound fruits. 

 All diseased fruits on the ground should be carefully collected as soon 

 as the} T fall; they should be removed from the orchard and destroyed 

 either by drying and subsequent burning or by burying them in a 

 deep trench, which is carefully covered with soil afterwards. Under 



