356 State Horticultural Society. 



SOMETHING ABOUT THE PEAR BLIGHT. 



Pear blight microbes are found in abundance in diseased tissue, can 

 be cultivated, and the disease reproduced in healthy trees. They can 

 not be killed by cold, but die at a temperature of very hot water.. The 

 host plants are the pear, apple, crab, quince, sar^^s berry, etc. The 

 microbes move en masse from one cell to another, breaking down the 

 cellular walls, passing in millions through and between. In blossom 

 blight the microbes appear in the nectar and penetrate the nectaries, 

 multiply and go down the stem. Bees visit the blossoms and carry the 

 microbes from flower to flower. The disease spreads with great rapidity; 

 only the brief time of blooming cuts this short. 



Spreading through the fruit spurs, these are killed to the bough. 

 The virus when it appears outside can be carried only by sepcial means — 

 birds and man. Even after blossoming, there is possibility of infection 

 of the green tips. The disease may also start in tender growing bark. 

 In artificial infection in the field it was never spread except where punct- 

 ures existed. When started in tender twigs, it spreads downward till it 

 meets cells too firm to be affected. From the fruit spurs it will spread 

 up and down, girdling the branch. If the woody cylinder is unin- 

 jured, the branch may live a year or more; but hot, thunderous weather 

 causes the microbes to overflow into the cylinder and the branch collapses 

 suddenly. The microbes die if they can not spread. 



If any of them live till fall, they may live over till sap runs in spring 

 and spread rampantly. The hold-over blight will spread upward and the 

 mummy virus run down, ready to spread the infection. The blight varies 

 according to the tree. Some varieties are easily attacked while others 

 are more or less immune. 



Treat the disease always as infectious. Watch every evidence and 

 destroy at once. With fruit spurs low down and sprouts on the trunk, 

 the blight gets quickly into the center of the tree. We must train and 

 prune our trees differently. To fight the disease, the vase form of top is 

 better than the pyramidal. Po produce the former, grow three shoots on 

 the stem, cut back and grow two on each of these, cut back and 

 grow two more and so on. This produces a low head broad 

 at the top, . with fruit spurs above and smooth limbs below. 



