BLACK ROOTROT OF THE APPLE ^ 



By F. D. Fromme, Plant Pathologist, and H. E. Thomas,^ formerly Assistant Plant 

 Pathologist, Virginia Agricultural Experiment Station 



INTRODUCTION 



An unusually destructive rootrot of the apple (Malus sylvestris) is 

 prevalent in the chief orchard sections of Virginia. The disease has 

 been known to the growers for a number of years, but it is only quite 

 recently that considerable interest has been manifested in it and a 

 technical study undertaken at the Virginia Experiment Station. 



The first pubHshed record of the disease, by Reed and Crabill (lo) 

 in 1 91 3, contains a brief mention of a rootrot, with the suggestion that 

 the cause may be one or more mushrooms. Subsequent preliminary 

 notes by the same authors (11) and by Crabill (i) have outlined the 

 general symptoms and indicated the importance of the problem. Fulton 

 and Cromwell (5), in an abstract, briefly described a "black rootrot" 

 of apple found in Pennsylvania and North Carolina which appears 

 very similar to and is probably identical with the disease under dis- 

 cussion. In a preliminary note the writers (3, 4) have stated that the 

 rootrot of apple in Virginia is probably due to one or more species of 

 Xylaria and have designated it "Xylaria rootrot." As a descriptive 

 common name "black rootrot" is preferable and will be used in the 

 belief that the assumed identity of the Virginia and North Carolina 

 rootrot diseases will be confirmed. 



The disease is most prevalent in the middle and north "Valley," 

 "Piedmont," and "Appalachian" sections of Virginia, and is probably 

 present to some extent throughout the State. Our information is based 

 on conditions as found in Alleghany, Rockbridge, Albemarle, Nelson, 

 Augusta, Rockingham, Botetourt, Montgomery, and Frederick Coun- 

 ties. Losses of trees ranging between 5 and 25 per cent of the entire 

 orchard have been observed. These losses, together with the high 

 death rate of replants, which will invariably exceed that of the original 

 trees in a stated period of years, make the disease a most formidable 

 one. Financial losses from rootrot are, of course, very considerable. 



SYMPTOMS OF ROOTROT 



Many of the superficial symptoms of the disease may equally well 

 characterize injuries due to other ageitcies such as winter injury, mal- 

 nutrition, attacks of mice or rabbits, tree borers, woolly aphis, crown- 

 gall, and collar-blight; but the combination of all symptoms, particu- 



• Paper No. 47 from the Laboratories of Plant Pathology and bacteriology, Virginia Agricultural 

 Experiment Station. 

 2 Now Assistant Plant Pathologist, Porto Rico Agricultural Experiment Station. 



Journal of Agricultural Research, Vol. X, No. 4 



Washington, D. C. July 23, 1917 



iv Key No. Va. (Blacksburg) — i 



(163) 



