90 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 



Clitocybe Root Rot 



W. A. Campbell 



Forest Service, U.S. Department of Agriculture, Athens, Georgia 



Clitocybe tabescens (Fr.) Bres. A destructive disease of fruit, 

 forest, shade and ornamental trees, shrubs, and vines mainly in the 

 Southeastern United States. Symptoms vary with the kind and size 

 of the host and the rapidity with which the fungus girdles the af- 

 fected plant. Sudden wilting is often the first symptom in broadleaf 

 trees ; however, yellowing, partial defoliation, and a general unthrifty 

 appearance are common top symptoms where girdling proceeds more 

 slowly. By the time top symptoms are evident, mycelial growth of 

 the fungus has progressed from the roots into the base of the tree 

 causing slightly sunken lesions which may extend upward from a 

 few inches to a foot or more above ground. Extensive mycelial fans 

 develop under the basal bark lesions and under the bark on diseased 

 roots. Mycelial mats vary from thin filmy wefts to leathery sheets 

 that are white when fresh out which become cream to chamois colored 

 with age. 



Fruiting bodies of the gill fungus Clitocybe tabescens may develop 

 at the base of affected plants depending upon the progress of the 

 disease and seasonal conditions. These may be sparse or abundant 

 in late summer and fall in the Southern United States, depending on 

 moisture and temperature. The fruiting bodies usually consist of 

 few to many individuals with the stems developing from a common 

 base. An annulus is lacking. When fully developed the caps are 

 convex to flattened or centrally depressed with age, whitish to light 

 tan or honey colored, smooth, or with tufts of fibrils near the center 

 and from 5 to 9 centimeters in diameter with whitish gills. 



Bresadola considers the American plant synonymous with Clitocybe 

 tabescens of Europe, however, judging from the lack of references 

 in the literature it causes little damage there. Root rot caused by 

 C. tabescens is similar to that caused by the closely related Armillaria 

 mellea Fr. and losses by these two fungi are probably confused in the 

 literature. Clitocybe root rot has been identified as the more serious 

 cause of mortaility in cultivated trees and shrubs. 



Range : In the United States mainly from eastern Texas, Oklahoma, 

 Missouri, southern Illinois, and Indiana, West Virginia, Virginia 

 southeastward to Florida. The fungus occurs north and west of 

 this range but rarely associated with root rot. It has been re- 

 ported from Madagascar and India. 

 Hosts: In Florida Clitocybe root rot has been recorded on 210 species 

 of plants belonging to 137 genera and 59 families, including Pin- 

 aceae, Cupressaceae, Casuarinaceae, Fagaceae, and Myrtaceae. 

 Literature : 



Bresadola, G. Inconographia mycologica V. 3, 150 pp., illus. 

 Mediolani. 1928. 



Owen, J. H., Miller, J. H., and Campbell, W. A. Clitocybe root rot 

 in Georgia. Plant Dis. Rptr. 44:89-91. 1960. 



Rhoads, A. S. Clitocybe root rot of woody plants in the Southeast- 

 ern United States. U.S. Dept, Agr. Cir. 853, 25 pp., illus. 1950. 



The occurrence and destructiveness of Clitocybe root rot of 



woody plants in Florida. Lloydia 19 :193-240. 1956. 





