232 AGRICULTURE 



soms. The germ is usually carried by bees from a 

 diseased tree to a healthy flower of pear or apple. The 

 fungus grows into the flower and on into the twigs. The 

 diseased twigs die. Pear-blight, unlike most diseases, does 

 least harm to trees that are growing slowly and thus form- 

 ing tough, short twigs. Hence, when a grown pear tree 

 is attacked, cultivation may be stopped, and no fertilizer 

 rich in nitrogen should then be used. 



Spraying is not a cure, but cutting in winter and through- 

 out the growing season all the diseased twigs helps to con- 

 trol the disease. Cut the twigs about one foot below the 

 diseased portion. After making each cut kill any germs 

 that may have lodged on the blade of the pruning shears 

 or knife. Do this by dipping the blade into a solution 

 of formalin or of carbolic acid or by wiping it on a cloth 

 dampened in a poisonous solution. Thus you will avoid 

 spreading the disease. 



EXERCISE. Find, examine, and show to your classmates specimens 

 of peach "mummies," rotting peaches or plums, diseased apples, curled 

 peach leaves, or spotted leaves of any fruit tree. Do the appearances 

 suggest that you are looking at the diseases here described ? 



NOTE TO THE TEACHER. Most State Experiment Stations will 

 identify diseased leaves or other specimens addressed to their bota- 

 nists and will furnish bulletins on plant diseases or tell you where to 

 get the bulletins that you may desire. 



