ASCOMYCETES 265 



Moreover, the data at hand seem to indicate that they occur 

 in all countries in which the host plants are commercially grown. 

 These fungi are apparently of economic importance in all sec- 

 tions of the United States where the weather may be cool and 

 damp during portions of the spring and summer. In the northern 

 portion of the United States it has received particular attention 

 at the agricultural experiment stations of Vermont, New York, 

 Illinois, also California, thus indicating a very general distribu- 

 tion. It is, however, believed to be equally distributed in the 

 Southeast, but in that section it has received less attention, per- 

 haps on account of the fact that the commercial output of these 

 fruits has not been a factor of such importance. In the past few 



FIG. 117. THE EFFECTS OF APPLE SCAB DURING A MOIST SEASON 



years these diseases have become a menace on the Pacific Slope. 

 All investigators, however, are agreed that cool, moist weather 

 either in spring or summer encourages the rapid spread of the 

 fungus, while hot winds quickly suppress it. 



Losses. It is not easy to estimate the average losses from these 

 fungi, and this is particularly true on account of the fact that the 

 scab fungi are more or less superficial in their effects. In severe 

 cases the fruit is wholly unmarketable, but in too many cases 

 scabby fruit is regularly put upon the market and the reduced 

 prices which it brings are not estimated. During seasons favor- 

 able for the fungus, probably one year in two, the losses in many 

 sections of the country amount to a reduction in price or total 

 destruction of from 25 to 50 per cent of the entire crop. 



