1646 



ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 



The man wlio knows nothing about bac- 

 terioloR>- would hardly considor himself 

 safe in experimenting with the anthrax 

 germ: neither should he consider himself 

 capable of experimenting with the pear- 

 blight germ. 



Summary 

 To those who have read the preceding 

 carefully, it may seem unnecessary to 

 add anything more, as it is believed that 

 all of the important facts about pear 

 blight have been clearly stated. How- 

 ever, a resume will bring before us all 

 the pertinent facts so that the reader may 

 see at a glance what he may want to 

 know without reading the text again. 



1. The history of pear blight dates 

 from the year 1780; the first record 

 was published in 1794 in the transactions 

 of the Massachusetts Society for the Pro- 

 motion of Agriculture. This first paper 

 on pear blight gave to the highlands of 

 the upper Hudson the distinction of be- 

 ing the birthplace of the disease. How- 

 ever, at the time of the discovery, the 

 disease had a wider spread throughout 

 the New England states than has been 

 recorded. 



2. The disease known as pear blight, 

 although of North American origin, has 

 found a foothold in Europe. 



3. The true character of the disease 

 ■was worked out by Professor T. J. Bur- 

 rill, of the University of Illinois, in 1878, 

 and was published to the world in 1880. 

 Dr. Burrill found that the disease is 

 caused by a small germ belonging to the 

 great family of bacteria, which are min- 

 ute, microscopic plants, the smallest 

 vegetable organism in the world. The 

 pear-blight bacillus is only 1/50,000 of 

 an Inch in diameter and about l/2.'5,000 

 of an Inch in length; under the micro- 

 scope, when magnified 1,000 diameters, 

 its appearance is that of a hyphen (-). 



4. The pear blight germ attacks all 

 species belonging to the pome or apple 

 family, and also in a small way infects 

 plums and the apricot. Among the cul- 

 tivated fruits, therefore, it attacks the 

 apple, pear, quince, lorjuat, plum and 

 apricot. The following wild fruits in- 



digenous to the Pacific Coast states are 

 also attacked by it. I shall give the com- 

 mon names and after them the botanical 

 or scientific names, so that students of 

 botany may be able to look them up: 



(a) Service berry or June berry 

 {Amelanchier florida). 



(b) Thorn apple or haw (Crataegus 

 douglasii). 



(c) Christmas berry or Toyon {Hete- 

 romcU's arbutifolia) . 



(d) Wild pear or apple (Malus di- 

 I'ersifolia) . 



(e) Mountain ash or rowan (Pyrus 

 sitchcnsis) . 



There are many more species of the 

 above genera to be found in the Eastern 

 and Southern states, but a knowledge of 

 the fact that all pome fruits blight should 

 be sufficient. 



5. The damage Ijy blight in the East- 

 ern and Southern states has been such 

 that practically all of the better varieties 

 or pears have gone out and commercial 

 pear growing is an industry of the past. 



6. The blight has spread into every 

 known section of the United States, South- 

 ern Canada and Northern Mexico; only a 

 very few small districts still remaining 

 free from it. 



7. The first appearance of the blight 

 is made evident by the blossoms and 

 young shoots becoming withered and 

 black, finally drying up. Later, branches 

 and limbs, as well as the bodies and root 

 system, become infected. Even the fruit 

 may become infected and wither away. 



8. The infections first noted in the 

 spring come from hold-over cases which 

 have resulted from the previous year's 

 infection. These hold-overs may be found 

 in the larger limbs, bodies and roots of 

 the pear, apple, quince, loquat and even 

 wild fruits, though less frequently Dur- 

 ing the blossoming period these hold- 

 overs ooze and this gummy substance, 

 which is filled with the bacteria, become 

 points for the starting of new infections 

 in the blossoms and twigs. 



9. The germs from the hold-overs are 

 carried about by liees and other inserts. 

 Biting and sucking insects cause infec- 



