io6 



AGRICULTURE FOR BEGINNERS 



If by chance your knife should cut into wood containing 

 the living germs, and then you should cut into healthy 

 wood with the same knife, you yourself would spread the 

 disease. It is therefore best after each cutting to dip your 

 knife into a solution of carbolic acid. This will kill all 

 bacteria clinging to the knife blade. After the leaves fall 

 in the autumn is the surest time to do complete trimming, 

 as it is easiest then to recognize diseased twigs, but the 



orchard should be carefully 

 watched in spring also. If 

 a large limb shows the blight, 

 it is perhaps best to cut the 

 tree entirely down. There 

 is little hope for such a tree. 

 A large pear grower once 

 said that no man with a sharp 

 knife need fear the fire blight. 

 Yet our country loses largely 

 by this disease each year. 



It may be added that win- 

 ter pruning tends to make 

 the tree form much new wood and thus favors the disease. 

 Rich soil and fertilizers in a similar way make it much 

 easier for the tree to "catch the blight." 



FIG. 90. FIRE BLIGHT BACTERIA 



Magnified 



EXERCISE 



Ask your teacher to show you a case of fire blight on a pear or 

 apple tree. Can you distinguish between healthy and diseased wood? 

 Cut the twig open lengthwise and see how deep into the wood and 

 how far down the stem the disease extends. Can you tell surely 

 from the outside how far the twig is diseased ? Can you find any twig 



