Pomaceous Fruits 53 



gummy exudate is usually present around the base of the tree 

 and black rhizomorphs adhere to the roots. In late stages 

 clusters of the gill-bearing sporophores (Fig. 25) develop; 

 Armillaria mellea Vahl. Quantities of black, stringy, hard, 

 shiny strands 1 to 2 mm. in diameter occur around the roots 

 and in the adjacent soil. The gilled sporophores appear later 

 (p. 370); Fomes annosus (Fr.) Cke. The sporophores are 

 pore-bearing (p. 371); 

 Septobasidium sps. with 

 smooth pore-bearing 

 surfaces; Ozonimn om~ 

 nivorum, Sh. See Texas 

 root-rot (p. 23); Xyl- 

 aria sps.^^ The affected 

 roots are covered with 

 a thin, compact growth 

 of mycelium, white at 

 first, later developing 

 into a black incrusta- 

 tion. Minute, thread- 

 like rhizomorphs ra- ^^V^^- -Br«wn-rot produced by inocu- 

 '^ . lation. JNote the lungus lorms the let- 



diate several centmie- ters A. M. C. Original, 

 ters along the root. 

 Affected roots are soon girdled and the distal parts die. 



Root-rot, due to one or another of these causes, is of wide 

 and common occurrence, and results in large loss. It is 

 found more frequently on newly cleared land than elsewhere. 

 When the disease has advanced far enough to be recognized, 

 no cure is available, and it is unsafe to replant in the infested 

 place. Wood bearing root-rot fungi should be burned to 

 lessen infection. 



Wood-rot '^'' of orchard trees is of the general character dis- 

 cussed under Decay in live trees on page 354. It is a very 

 important source of loss on fruit trees of all kinds, about 

 one-half of all bearing trees being infected. The rot may 

 chiefly be avoided by preventing wounds or by treating them 

 with disinfectants. See p. 378. 



