CLITOCYBE ROOT ROT OF WOODY PLANTS 



9 



The mycelial sheets that develop under the bark are coextensive with 

 the lesions (fig. 4). 



In certain species of Australian pine trees the basal girdling by root 

 rot frequently stimulates a pronounced hypertrophy of the trunks im- 

 mediately above the girdled parts. Stone-fruit trees, such as peach, 

 plum, and Carolina laurelcherry, commonly develop more or less gum 

 formation in the cambial region, which may be so copious as to exude 

 through cracks in the bark. 



Figure 4. — Large guava tree dying from Clito.cybe root rot. Dead bark has been 

 cut away on basal lesion to show extent to which mycelium has spread up trunk. 



When the bark of roots attacked by Clitocybe root rot is peeled off, 

 the mycelium of the fungus is seen to have developed between the bark 

 and the wood (fig. 5) and also through the inner layers of the bark. 

 This varies from thin, filmy wefts to leathery sheets that are white 

 when freshly developed but become cream- to chamois-colored with 

 age. The mycelial sheets often shoiv a more or less radiating, fan- 

 shaped type of development, but this feature is less conspicuous than 

 usually occurs with Armillaria mellea and is less apparent in old, 

 compact mycelial sheets. When especially favorable soil moisture 

 conditions induce an unusually luxuriant growth, the advancing mar- 



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