172 Journal of Agricultural Research voi. x. No. 4 



on the surface of affected roots and the accompanying dark zonations in 

 the bark and wood are rehable diagnostic features. 



Field observations show that rootrot is infectious. The progress of 

 the disease indicates an attack of a comparatively slow working parasite. 

 Two or more years of infection are probably required to produce the 

 death of the tree. 



Apple trees planted on newly cleared land are more liable to attack 

 than those on land cleared and cultivated for some time before planting. 



Three species of Xylaria have been obtained in pure culture from 

 affected apple roots. X. hypoxyion obtained from orchards at nine 

 places proved to be an active wound parasite on living apple roots in 

 moist chambers and in the field. Typical black rootrot symptoms were 

 produced and recovery in pure culture was obtained. Xylaria sp. 

 (undetermined) from one source also proved pathogenic, X. poly- 

 morpha from two orchards at one place proved only slightly, if at all, 

 pathogenic. X. hypoxyion is probably the chief cause of black rootrot 

 of the apple in Virginia. 



Exclusion practices are suggested as control measures of probable 

 value. 



LITERATURE CITED 

 (i) Crabh^l, C. H. 



1916. NOTE ON APPLE-ROT IN VIRGINIA. In Phytopathology, v. 6, no. 2, p. 



159-161, I fig. 



(2) Freeman, Linford. 



I9IO. UNTERSUCHUNGEN tJBER DIE STROMABILDUNG DER XYLARIA HYPOXYLON 



IN KUNSTUCHEN KULTUREN. hi Ann. Mycol., V. 8, no. 2, p. 192- 

 211, 14 fig., pi. 4 (col.). 



(3) FrommE, F. D., and Thomas, H. E. 



1917. THE ROOT-ROT DISEASE OF THE APPLE IN VIRGINIA. In Science, n. s., 



V. 45, no. 1152, p. 93. 



(4) 



1917. A XYLARIA ROOT-ROT OP THE APPLE. (Abstract.) In Phytopathology, 

 V. 7, no. I, p. 77. 



(5) Fulton, H. R., and Cromwell, R. O. 



1916. BLACK root-rot OP THE APPLE. (Abstract.) In Phytopathology, v. 

 6, no. I, p. no. 



(6) Gu6guEn, Femand. 



1907. RECHERCHES BIOLOGIQUES ET ANATOMIQUES SUR LE XYLARIA HYPO- 



XYLON. In Bul. Soc. Mycol. France, t. 23, fasc. 4, p. 1S6-217, pi. 

 21-22. 

 (7) 



1909. l'^TAT CONIDIEN DU xylaria POLYMORPHA GBEV. trVDlt DANS SES 



CULTURES. In Bul. Soc. Mycol. France, t. 25, fasc. 2, p. 89-97, pi. 4. 



(8) Harder, Richard. 



1909. BEITRAGE ZUR KENNTNIS VON XYLARIA HYPOXYLON (lIN.). In Na- 



turw. Ztschr. Forst. u. Landw., Jahrg. 7, Heft 8, p. 429-436, fig. 1; 

 Heft 9, p. 441-467, fig. 2-17. 



(9) Jensen, C. N. 



1912. FUNGUS FLORA OF THE SOIL. New York (Cornell) Agr. Exp. Sta. Bul. 

 3x5, p. 413-50I' fig- 100-134. 



