\i)() A B1o>isoin Wilt and Canher of Apple Trees 



in some cases well-developed chains of conidia were produced within 

 twenty-four hours after placing the dead trusses in the moist chamber. 

 Pustular outgrowths were observed on some of the recently produced 

 (from infection in 1915) cankers in August but they were barren and no 

 conidia were found on them before December. 



Old dead spurs bearing conspicuous pulverulent pustules of conidia 

 during the summer months were present on some of the trees in the row, 

 and in those cases where cankers had been caused these too had the 

 conidial tufts scattered over the cankered surface, particularly towards 

 the periphery. These in all probability were the result of infection 

 during the previous flowering season of 1914. That these dead spurs 

 and cankers were the source of infection resulting in the blossom wilt 

 of 1915 and that the fungus on them was the cause of the injury was 

 suggested by the fact that the newly killed trusses were most numerous 

 on those trees bearing the greatest number of old spurs and cankers and 

 were most frequently met with in their vicinity. Trusses within a short 

 distance below such spurs and cankers were particularly liable to 

 infection ; thus on one branch of a Duchess' Favourite tree a portion 

 one foot in length bore nine dead trusses, three above and six below a 

 dead spur with its accompanying canker on which were numerous 

 conidial fructifications of the Monilia—thTee of the dead trusses were 

 on the spurs immediately below the canker. (This canker is shown in 

 Fig. 2.) 



The relation between the number of dead spurs and the number of 

 wilted trusses per tree showed, although the disease may spread from 

 afEected trees to others in the neighbourhood, it may be stated generally, 

 particularly if the trees are well separated from each other, that the 

 wilted trusses are infected from spurs or cankers on the same tree. 



The forty-eight trees in the row had in all seventy dead spurs (some 

 with cankers) bearing the fungus; the number of dead trusses was 1319, 

 and since there was no other source of infection in the immediate 

 vicinity it must be assumed that the wilted trusses of these trees were 

 infected from the seventy dead spurs ; that is to say that in that year 

 each old spur was responsible on the average for the death of nineteen 

 trusses of blossom. A search in the neighbourhood of a group of closely 

 aggregated dead trusses almost invariably revealed the presence of one 

 or more dead spurs bearing the fungus. 



Infection occurred through the flowers and not through the leaves 

 as shown by the fact that primarily the flowering trusses only are 

 attacked. On one of the trees (variety Warner's King) was a branch 



