48 



A " Wither Tip " of Plum Trees 



Later results were as follows: 

 July 11 



3. Inooulatod plum .'-•hri\-ollt'd, the other 

 plum attached to it by hyphal jmd and 

 discoloured for about one-third of its 

 surface. These two plums were re- 

 moved and photo<;raphed on this date 

 (see PI. IX, Fig. 5) 



4. Inoculated plum dr\' and shrunken, 

 stalk brown to base; the other plum 

 wrinkled, its wh(-le surface discoloured 

 and bearing numerous pustules; brown- 

 ing extending along stalk for 2 mm. 

 from the plum 



5. Inoculated plum with stalk brown to 

 base 



6. Both plums shrunken and wrinkled; 

 stalk of each brown and sulcate 



7. Inoculated plum wrinkled and shrunk- 

 en, numerous pustules present, stalk 

 brown to base, and detached from the 

 spur but fruit supported by its attach- 

 ment to the other plum; the latter 

 shrunken, bearing numerous pustules 

 .scattered over the discoloured surface, 

 stalk brown to base 



8. Inoculated plum shrunken, stalk brown 

 nearly to base, the other plum attached 

 by hyphal pad but not showing any rot 



9. Inoculated ])lum on the ground, surface 

 wrinkled, no rot in second plum 



10. Inoculated plum wrinkled and shrunk- 

 en, stalk brown to base; the second 

 plum is somewhat shrunken, has 

 nuiTierous pustules scattered over the 

 surface, stalk brown nearly to base 



July 20 



Both plums quite diy, wrinkled and much 

 shrunken, surface of both bearing numer- 

 ous pustules with powdery conidia; 

 stalks brown to the base 



No further change evident; no rot on the 

 second jilum 



Inoculated plum detached from spur but 

 remains suspended ])y its attachment to 

 the other 



No further chanLre noticeable 



Inoculated plum wrinkled and shrunken, 

 stalk brown to base and detached from 

 spur but plum remains suspended by 

 attachment to the other 



8till no rot in the second plum 



Both plums fallen 



The experiments prove conclusively that the strain of Monilia 

 cmerea obtained from a withered plum twig was able to produce a 

 "brown-rot" of the fruit when the conidia have access to wounds 

 through the skin; conidia placed on the uninjured skin gave negative 

 results in all cases and it would a})pear therefore that conidia falling on 

 uninjured plums are unable to produce the rot. When however a healthy 

 plum is in contact with an infected one the mycelium in the latter may 

 produce a dense pad of hyphae at the point of contact, thus enabling it 

 to penetrate the skin at that spot and set up a rot in the adjacent plum. 

 When two plums are in contact the cuticle is probably injured by the 

 frequent chafing resulting from the motion of the branch in the wind, 

 for it was noticed that round the point of contact the waxy "bloom" 

 was removed from the skin. 



