Peach IvKaf-Curi.. 377 



same sections in 1897 saw a large increase in the abundance of 

 the disease, and the past season was characterized by unusual 

 injuries from this cause. This wave of increasing abundance 

 during the past few years seems to have extended quite gener- 

 ally through the Northern States, judging from inquiries 

 received, and from the activity of experimenters in this field of 

 work at various experiment stations. 



Attempts have been made specifically to define the conditions 

 which encourage the curl. Some have asserted that a cool, 

 moist spring is most conducive to its abundance. The time of 

 infection, however, should be determined, it seems, before any 

 satisfactory explanation may be given. It is quite reasonable to 

 suppose that the conditions prevailing at the time the spores of 

 the fungus are being disseminated, or the conditions prevailing 

 at the time the spores germinate to infect the buds or leaves 

 would be the factors to determine the greater abundance or the 

 less abundance of the disease the following year. If the spores 

 of the fungus live over winter on the ground or twigs, and ger- 

 minate with the first warm days of spring to infect the opening 

 buds, then the spring conditions would seem to be of great 

 importance in determining the amount of the disease. If, how- 

 ever, infections result during summer or autumn the eifect of 

 spring conditions is not apparent. 



It is well known that different varieties of the peach show dif- 

 ferent degrees of susceptibility to the attacks of leaf -curl. The 

 same is often found to be true of other plants attacked by other 

 fungous diseases, and it can only be explained by constitutional 

 dift'erences in the varieties. Among varieties of peaches ver}^ 

 susceptible to the curl, Selby* mentions Mountain Rose, Old 

 Mixon, Globe, Elberta, Scott's Nonpareil, Red Cheek, and 

 others. Such a list will, in all probability, vary with the place, 

 and I have examined some orchards of man}^ varieties in which 

 none were exempt. 



e. Kennedies. 



The early experiments made to determine the value of fungi- 

 cides for the prevention of peach curl were unsatisfactory both 



'"Bulletin 92, Ohio Agricultural Bxp. Station, 1898. 



