THE LEAF BLOTCH DISEASE OF HORSE-CHESTNUT 



4i5 



the activities of the fungus. Rainy periods throughout the summer 

 favor the growth of the trees, since sufficient moisture is supplied for 

 their development. On the other hand, wet weather also affords the 

 necessary conditions for the pathogene. With the presence of moisture 

 the fungus spores are able to germinate and produce infections when they 

 fall on the leaves of the trees. For the control of the leaf blotch disease, 

 therefore, it is necessary to check the attack before suitable conditions 



FlG. 88. A HAND DUSTING MACHINE 



This duster is suitable for dusting small trees 



are afforded for the germination of the spores on healthy foliage. It is 

 impossible to check the activities of the parasite in the affected leaf after 

 the spores have germinated and the germ tubes have gained an entrance 

 into the leaf tissue. 



As previously stated, the first infections in the spring are produced 

 by spores from the perithecia in old dead leaves on the ground. Un- 

 doubtedly much damage can be prevented by plowing under or burning 

 the old leaves before the new foliage is developed. A large proportion 



