IHf^ A Blossom Wilt and Canker of Apple Trees 



a distance of 19 cm. or from 3 cm. above truss (a) to 7 cm. below (d); 

 the terminal portion of the branch died as a result. 



The fungus itself was not observed until the first week in December 

 when young pustules with chains of immature conidia (the conidia 

 remained cohering in chains when particles of the pustules were mounted 

 in water) were seen at the lower end of the canker. Later others appeared 

 and by Jan. 9 numerous conspicuous pustules were present along the 

 whole length of the canker and on the infected spurs. By this time the 

 conidia were more or less pulverulent as a considerable number became 

 free on mounting in water ; such conidia were viable and many of them 

 germinated within forty-eight hours when the slide was kept in a damp 

 chamber at a temperature of 6° to 8° C. 



(e) On another branch a truss was infected by placing conidia at 

 the base of the styles of one flower on April 8. The truss wilted before 

 the end of the month and a canker developed which had nearly girdled 

 the branch when examined on June 8. Immature Monilia pustules 

 were present at the base of the spur on Dec. 6 ; these were well developed 

 by Jan. 9. 



(/) On the same branch as {e) a similar truss was infected by 

 placing conidia on the stigmas of a flower. The spur was killed before 

 April 26, but no canker was produced on the branch. One Monilia 

 pustule was found on the spur on Jan. 9. 



(g) A truss inoculated on April 11 was dead within fifteen days. 

 On April 27 the twig bearing it was removed from the tree and it was 

 found that the tissues of the spur (which was 1 cm. in length) were 

 brown to the level of its insertion on the twig and the disease was 

 already encroaching on the tissues of the twig itself. In sections made 

 transversely through the spur there were found numerous hyphae, 

 particularlv in the pith, and particles of the sections placed on an agar 

 plate produced mycelial growth resembling that obtained in a similar 

 manner from naturally infected spurs. 



The exact date when the trusses of this variety first showed signs of 

 wilting was not ascertained, but all those referred to above were dead 

 on April 26 and had probably begun to wilt some days previously. The 

 varieties which were treated at a later date were examined more fre- 

 quently and the earlier symptoms of the disease noted. 



