88 Disease of Fnilt Blossom 



of the petals. The remaining parts of the flower may or may not be 

 attacked in due course. In the latter event the affected petals fall as 

 the flower ages, and the young fruit may then develop normally. 



While attacked flowers at times remain attached to the fruit spur 

 for a comparatively long period, even when the disease has obtained a 

 strong hold, it is very common to find flowers which fall at the slightest 

 touch, although the external signs of disease are limited to a few small 

 black spots on the receptacle. A slight shaking of the tree suffices to 

 cause blossoms in all stages of development to fall in showers. Young 

 fruits which appear to have just set are particularly liable to come off' in 

 this manner. Examination of the internal parts of the flower in such 

 cases generally shows that the ovary is more or less completely 

 blackened. 



The disease spreads very rapidly from flower to flower ; and, if it 

 makes its appearance when the tree is just beginning to blossom, it may 

 spread to nearly all the flowers on the tree during the three to four weeks 

 over which the latter is carrying open blossom. 



While the disease in its most serious form is concerned mainly with 

 the flowers, other parts of the tree are attacked. The young leaves 

 which appear during the blossoming season frequently show small 

 black spots or areas, very similar in general character to the blackened 

 spots which occur at the points of infection on the petals. Serious 

 damage to the foliage does not generally result, the spots remaining 

 small and eventually drying up and falling out. The leaves developing 

 around the blossom trusses on the fruit spurs are usually most severely 

 attacked. The disease on the foliage generally starts at the tip of the 

 leaf, but occasionally at some point along the margin. 



The fruit spurs of the tree are also often attacked ; and it is possible 

 that this feature of the disease may prove to be the most serious. Refer- 

 ence has already been made in passing to the fruit spur attacks when 

 describing the course of the disease of the blossom trusses : and it has 

 been shown that after the death and fall of the flowers of the truss the 

 spur is left as a barren stump, which sometimes dies back as far as the 

 point of its attachment to the branch carrying it, but occasionally sur- 

 vives and produces lateral growths which develop in due course into 

 either shoots or branch spurs. In both cases the tissues of the spur 

 are attacked by the bacillus. When death of the spur results, apart 

 from the loss of the spur by the tree no evil effects may follow ; but if 

 the spur survives, the infected tissues harbour the organism throughout 

 the summer and winter and may prove to be responsible for an outbreak 



