58 Zessons in Fruit Growing. 



soil as above described, and in planting orchard trees, to- 

 bacco dust should be freely used about the roots. Ap- 

 ple seedlings and root grafts should be planted suffi- 

 ciently deep so that they stand in a shallow trench, which 

 should be filled with powdered tobacco or tobacco dust 

 lightly covered with earth. Newly-cleared land should be 

 cultivated two years before planting with apple trees, to- 

 rid it of the woolly-aphis. 



62. The fire blight ^ {Micrococcus amylovorus) is a bac- 

 terial disease that affects all of the pome fruits. The spores 

 of the bacteria enter at the tips of growing shoots, or 

 through the open flowers or wounds made by insects, and 

 the disease works its way backward, destroying the tissues 

 as it proceeds, causing the foliage and wood to assume a 

 blackish-brown color and to emit a characteristic odor. It 

 affects the pear and quince more than the apple, as it pro- 

 gresses much faster in these fruits. The more succulent 

 the tissue of the young growth, the more likely is it to be- 

 come infested with fire blight and the more rapidly the 

 disease progresses. 



Preventive measures. Since over-succulent tissue favors 

 infection by fire blight, stimulants to excessive growth, as 

 thorough cultivation and heavy nitrogenous manuring 

 should be avoided. Free circulation of air about the tree 

 should be encouraged. Infested shoots should be cut off 

 and burned as soon as discovered. They should be cut six 

 or eight inches below the point of visible infection, as the 

 dead tissue marks the points to which the disease has fin- 

 ished its work, rather than commenced it. 



63. The scab fungus {Fusicladium) affects the apple and 

 pear, causing blackish, scabby spots upon the fruit which 



* Known also as " pear blight," " apple blight," or simply " blight." 



