6o Journal of Agricultural Research voi.iv, no. i 



abundance. Under ordinary conditions, even with the weather favor- 

 able to the development of the fungus, bitter-rot may be practically 

 prevented by spraying with Bordeaux mixture. When, however, in 

 addition to favorable weather conditions, the primary sources of infec- 

 tion are as abundant as they are in some of the orchards of the Ozarks 

 and probably other sections in which the disease is prevalent, spraying 

 alone will, by reducing the number of infections, only retard rather than 

 prevent. To gain success by spraying it would be necessary to keep 

 the entire surface of every apple continually covered with Bordeaux 

 mixture, a physical impossibility. 



HISTORICAL REVIEW OF LITERATURE 



The early infections of bitter-rot have been explained somewhat differ- 

 ently by different writers, all of whom doubtless give correct explana- 

 tions for the particular regions or orchards in which their investigations 

 were made. None of these writers, however, has made his investigations 

 complete enough to account for the numerous early infections which 

 sometimes occur. 



Simpson, of Illinois, discovered that primary infections of bitter-rot 

 were associated with a certain type of twig canker (Burrill and Blair, 

 1902, p. 355; Von Schrenk and Spaulding, 1903, pp. 30-31). ^ 



Burrill and Blair (1902, p. 356) discuss the fungus in relation to early 

 infections as follows : 



It therefore became evident that the disease on apples could come from these spots 

 on the branches, and e very-thing now goes to show that except in the few cases that the 

 rot mummies hang over on the trees, the first or early infection comes solely from these 

 limb cankers. * * * it now seems to be commonly true that the cankers are few 

 in number, at least upon the kinds of trees ordinarily planted in Illinois and not over 

 15 years of age. 



Clinton (1902) expresses the belief that the early infections come from 

 the ascogenous stage of the fungus, developing in mummies of the pre- 

 ceding year. 



Hasselbring found that in mummied apples kept out of doors the fungus 

 ordinarily retains its vitality in a dormant state in the v/inter and in May 

 or later under proper conditions again begins to produce conidia (Burrill 

 and Blair, 1902, p. 354). 



Von Schrenk and Spaulding (1903, pp. 37-38) showed by inoculations 

 that the limb cankers discovered by Simpson were actually caused by the 

 bitter-rot fungus. They also state : 



The apparently erratic behavior of the bitter rot can be explained in part since the 

 discover}' of the canker stage of the fungus. After its introduction into an orchard 

 or" on one tree the fungus attacks one or more branches, probably early in the summer, 

 and produces a canker. The next y^ear the spores from this canker will be washed 

 down on the ripening fruit by a rain. The water is sprayed from the branch on which 

 the canker is situated to the lower branches in the form of a cone, and one or more 

 spores will probably fall on every apple within such a cone. The presence of the 



1 BiblioEraphic citations in parentheses refer to " Literature cited." p. 64. 



