FIRE BLIGHT. 



119 



ber of conditions which affect the character 

 and progress of the disease. 



Every tree of the pome family is sub- 

 ject to the Wight, but pears and quinces are 

 more susceptible than plums and apples. 

 The mountain ash, service berry and haw- 

 thorn are frequently diseased, but not to 

 such an extent as the first named trees. 

 There is a difference in the susceptibility of 

 varieties. Thus among pears, Clapp's Fa- 

 vorite, Flemish Beauty, and Bartlett, are 

 more liable to the disease than Keiffer and 

 Duchess, and amongst apples the crab varie- 

 ties are the least resistant. 



CHmatic conditions influence the disease; 

 warm, moist weather with much rain favor 

 it; whilst bright, dry, sunny weather tends 

 to check it. 



High cultivation, rich soil, heavy manur- 

 ing, free use of fertilizers, heavy pruning, 

 or any other treatment which has a ten- 

 dency to induce new and succulent growth, 

 favors the disease, as the bacteria grow with 

 far greater rapidity and penetrate more 

 quickly from cell to cell when the tissues are 

 gorged with sap. Insects are more partial 

 to young succulent shoots and leaves, and 

 the bites and punctures of such insects, 

 whose mouth parts may be contaminated 

 with pear blight germs, often serve to infect 

 the tree. 



It is thus manifest that healthy, thrifty, 

 vigorous, well fed and well cultivated trees 

 are more liable to the disease than others, 

 and hence the severity of an attack of fire 

 blight may be lessened by conditions which 

 are under the control of the grower. 



Treatment. — The treatment of fire blight 

 is of two kinds, that which is designed to 

 put the tree in a condition to withstand the 

 attack of the blight microbe, and those 

 methods which aim at the extermination of 

 the casual bacterium. Unfortunately all 

 methods which are used for hindering the 

 attack of the microbe consist of restraining 



the full development of the tree, and hence 

 any such system of procedure should not be 

 followed unless an orchard is very badly 

 attacked. 



High cultivation, winter pruning and 

 other conditions already mentioned as pre- 

 disposing trees to blight should be aboided, 

 but the trees should be allowed to ripen the 

 wood, and in order to do this the fruit 

 grower must use any method which will 

 check the amount of moisture in the soil, for 

 instance, by the growth of a clover crop. 



The fire blight organism cannot be ex- 

 terminated by spraying, as the microbe lives 

 in the tissues beneath the outer bark, and it 

 is impossible to reach it with any spraying 

 solution, for unless the bacteria come into 

 contact with the germicide spraying is in- 

 effectual. 



There is therefore but one remedy, to cut 

 out and burn the affected parts of the tree. 

 It is very necessary when cutting out a dis- 

 eased branch or twig to cut well below the 

 discolored portion, as the bacteria are in 

 teria; so that if only the discolored portion 

 the discoloration not being produced imme- 

 diately upon the appearance of a few bac- 

 teria, so that if only the discolored portion 

 were cut off numbers of bacteria would still 

 be left in the stump, and these would con- 

 tinue to multiply, and the disease would 

 soon be evident again. 



Cutting off affected parts may be done at 

 any time in the winter and spring, but it is 

 not advisable to cut in the growing season, 

 as fresh cases may be constantly occurring, 

 and these, owing to lack of sufficient devel- 

 opment, would not be seen. 



The best time for cutting out affected 

 branches is towards the fall, or when the 

 trees have stopped forming new wood,, when 

 most of the blight has developed, and when 

 the contrast between the discolored leaves 

 and branches and healthy tissues is easily 

 seen. 



