PEACH SCAB AND ITS COjSTTEOL. 



45 



disease before early varieties are harvested. On raidseason varieties 

 under conditions favoring the 'development of the disease, there is 

 time for very serious injury to result. On late varieties the great 

 increase in opportmiities for infection and incubation are attended 

 by consequent increment in the severity of the disease. The earHer 

 varieties as a group are thus more properly designated as disease- 

 escaping than as resistant, since they may be quite seriously scabbed 

 when conditions unusually favor the early development of the disease. 



While the period of exposure of the fruit to the attack of the 

 lungus appears to be a major factor in these varietal differences, it 

 is evident that other causes are involved. It has been noted that 

 certain varieties growing in adjacent rows and ripening at about 

 the same time have been attacked by scab in very different degrees 

 and that certain of the earher varieties are commonly more seriously 

 affected than some of those which ripen later (Table IX). It is also 

 a matter of common observation that seedhngs are often especially 

 severely attacked. No attempt has been made to investigate the 

 further causes miderlying these variations. 



At the writer's request Mr. M. B. Waite, Pathologist in Charge of 

 Fruit-Disease Investigations, Bureau of Plant Industry, has prepared 

 a list of important commercial varieties of peaches grown in the Mid- 

 dle States, with estimates concerning the degrees in which they are 

 subject to scab injiu-y in this territory. These estimates, which are 

 based upon more than 25 years of experience and observations 

 extending over all the important peach-producing districts of the 

 area in question, are incorporated in Table IX. 



Table IX. — List of important commercial peach varieties, with estimates of the compara- 

 tive degrees in which they are subject to injury by Cladosporium carpophilum in the 

 Middle States. 



Variety. 



Estimated decrease 

 ia market value 

 of unsprayed 

 crop due to scab 

 injury (per cent). 



Variety. 



Estimated decrease 

 in market value 

 of unsprayed 

 crop due to scab 

 injury (per cent). 





In aver- 

 age 



seasons. 



In bad 



seasons. 



In aver- 

 age 

 seasons. 



In bad 



seasons. 



Alexander. 



25 

 40 

 15 

 30 

 30 

 40 

 15 

 10 

 30 

 15 

 25 

 35 

 30 



50 

 80 

 30 

 60 

 60 

 80 

 30 

 20 

 60 

 30 

 50 

 70 

 60 



Oldmixon 



40 

 35 

 35 

 25 

 25 

 30 

 25 

 40 

 50 

 60 

 70 

 75 



80 





Elberta 



70 



Hale Early 



Chairs 



70 



Waddell 



Late Crawford 



50 



Carman 



Edgemont 



50 





Stevens 



60 



Hiley 



Fox ( Fox Seedling) 



50 



St. Tohns 



Smock 



70 



r-hampinn 



Heath 



90 





Salway 



90 



Belle 



Bilyeu 



95 



Beeves 



Tennessee 



100 



Ptnrnp 











