SOURCES OF APPLE BITTEE-EOT INFECTIONS. 7 



In many Virginia orcliards the lower limbs when laden with 

 fruit reach to the ground. In such cases the disease could be found 

 first on the fruits in contact with those of the previous season on 

 the ground. From these infected fruits spores could easily be car- 

 ried to sound ones. 



The writer has frequently attempted to find the fungus in mum- 

 mies and rotted fruits which w^ere more than a year old, but has been 

 uniformly unsuccessful. Those upon the trees appear to be dried up 

 so thoroughly at the end of a year that they drop from the tree; 

 those on the ground finally become almost wholly disintegrated 

 through the action of molds and bacteria. 



In Virginia, therefore, mummies and rotted fruits, being more 

 prevalent, are of more importance as sources of infection than they 

 are in ISIissouri and Arkansas. In the last-named States cankers may 

 overshadow them in importance. 



BITTER-ROT CANKERS. 



REVIEW OF THE LITERATURE. 



In 1902 R. A. Simpson discovered that in Illinois a certain type 

 of canker was associated with outbreaks of bitter-rot. He found 

 that if search was made shortly after the first outbreak of the dis- 

 ease such cankers were to be found just above a clump of infected 

 fruits. Simpson's discovery was announced at about the same time 

 by Burrill and Blair (4) and by Von Schrenk and Spaulding (13). 



Burrill and Blair (4) in 1902 stated that Hasselbring had shown 

 the fungus found in these cankers to be identical with the bitter-rot 

 fungus. Hasselbring found that the fungus from the cankers would 

 cause typical bitter-rot when introduced into sound apples. 



Von Schrenk and Spaulding (13) in 1903 also showed that spores 

 from the cankers could cause tjq^ical bitter-rot when introduced into 

 sound apples. They further showed that spores could be washed 

 from the cankers by water and that when falling upon apples they 

 could produce bitter-rot. To determine whether or not the Glomer- 

 ella could actually be the causal organism involved in the production 

 of cankers, they inoculated sound branches with spores (conidia) 

 from pure cultures. As a result of these inoculations cankers were 

 formed which showed the characters of the cankers found by Simp- 

 son. From these artificial cankers Von Schrenk and Spaulding re- 

 isolated the fungus and also inoculated apples with conidia produced 

 in the cankers. They describe the development of the artificially pro- 

 duced cankers as follows: 



Several weeks elapsed before there was any evidence of development on 

 the limbs. In both the inoculated slits and tne control slits the bark dried 

 somewhat along the edges of the slit, making a gaping wound. After some 



