82 MANUAL OF TREE DISEASES 



trenches, a foot or two deep. All roots bridging the trench 

 must be removed and the trench kept free of debris and fruit- 

 ing-bodies. The trench must be dug far enough away from 

 the affected trees to insure the absence of diseased roots out- 

 side of the area to be isolated. 



References 



Long, W. H.. The death of chestnuts and oaks due to Armillaria 



meUea. U. S. Dept. Agr. Bui. 89 : 1-9, pis. 1-2. 1914. 

 Schrenk, Hermann von, and Spaulding, P. Root-rots. In Diseases 



of deciduous forest trees. U. S. Dept. Agr. Bur. PI. Ind. Bui. 



149 : 22-24. 1909. 

 Hesler, L. R., and Whetzel, H. H. Armillaria root-rot. In Manual 



of fruit diseases, pp. 96-102, figs. 26-27. 1917. 

 Hartig, R. Agaricus meUeus L. In Die Zersetzungserscheinungen 



des Holzes etc., pp. 5&-62, pi. 11. 1878. 

 Hartig, R. Agaricus (Armillaria) malleus L. In Wichtige Krank- 



heiten der Waldbaume, pp. 12-42, pis. 1-2. 1874. 

 Lawrence, W. H. Root diseases caused by Armillaria meUea in the 



Puget Sound country. Washington Agr. Exp. Sta. Bui. (special 



series) 3 : 1-16, figs. 1^. 1910. 

 Piper, C. v., and Fletcher, S. W. Root diseases of fruit and other 



trees caused by toadstools. Washington Agr. Exp. Sta. Bui. 



59 . 1-14, figs. 1-5. 1903. 

 Horne, W. T. The oak fungus disease of fruit trees. California State 



Com. Hort. Monthly Bui. 3 : 275-282, figs. 79-81. 1914. 

 Home, W. T. Fungous root rot. California State Com. Hort. 



Monthly Bui. 1 : 216-225, figs. 85-91. 1912. 

 Horne, W. T. Oak fungus or Armillaria mejlea in connection -nith 



nursery stock. Califomia State Com. Hort. Monthly Bui. 4: 



179-184, figs. 31-33. 1915. 

 Barss, H. P. Mushroom root rot of trees and small fruits. First 



Biennial Crop Pest and Hortieultiu*al Report (Oregon Agr. Exp. 



Sta.) 1911-1912 : 22&-233, figs. 23-38. 1913. 



^NItcorhizas 



Caused by various species of fungi 



An interesting type of parasitic relation between certain 

 species of f imgi and the living roots of many kinds of trees con- 



