A I it
 l Spraying Apple Trees. . 63 t
  cause of the part commonly attacked, but it is the same disease as  
 ’ the pear blight, though affecting pear trees somewhat differently it
 f and often moreinjuriously. It is none the less an annoying dis- P  
  ease in young apple orchards and sometimes in nurseries, attacking · 1 j
ih the most thrifty trees rather more frequently and severely than the I i
_.  others. _t
 it Like pear blight, it varies much in prevalence with season, and   t
  fruit growers claim certain varieties are more subject to it than  
 ? others, an opinion which my observations tend to confirm.    
  When some of the sap from the blighted twigs is examined with t i
 ’ a high power of the microscope, it is found to swarm with minute  
V slightly elongate bacteria, the Bacillus amylovorus, diseoveredby  
 Z Professor T. J. Burrill, of Illinois, in 1879. tt
  It is especially troublesome during very hot weather following  
  periods of excessive rainfall. The organism is easily detected by ‘ t 
, a good microscope worker. At times a sort of fermentation takes  
 ‘ place within the diseased twigs, and the sap exudes and dries, form-    
;_ ing an opaleseent mass consisting almost entirely of bacteria. t 
` Similar masses are sometimes seen on the trunk when blight canker  It
_;  I occurs. The bacteria are easily grown on artificial media, and may  
  be made to produce the disease in sound wood by injecting them.  
A The germs remain in some of the diseased trees over winter, and  
are probably carried from them by insects the following spring to  
I healthy trees. Insects very often convey the disease at this time  ft,
2 to blossoms, and it extends down the fruit spurs. The bacteria  
J have been detected on the jaws of the honey bee, from which we  
_ may infer that even this useful insect at times carries the taint  Qt
° from one tree to another. Some years ago, Professor Chester, of  
" Delaware, in order to show the manner in which the blight is con-  
< veyed through the blossoms, removed some of the germs from blight-  
L Gd wood, mixed them with water and then with a. camcl’s hair brush  
wig- _ simply moistened the stiginas of blossoms with the water. The  
the · blight penetrated the blossoms and extended into the wood to which _ 
. they were attached, exactly as it does in nature.  
p When this disease is once in tl1e bark of trees external appli- t 
cations can do but little good, and the procedure adopted by growers Q 
  cutting out blight systematically and persistently whenever dis-  
covered, winter and summer. Once exterminated on a place it is  
 
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