Circular No. 853 



December 1950 



Washington, D. C. 



UNITED STATES DEPARTMENT OF AGRICULTURE 



Clitocybe Root Rot of Woody Plants in 

 the Southeastern United States 



By Arthur S. Rhoads, 1 formerly pathologist, Division of Forest Pathology, 

 Bureau of Plant Industry, Soils, and Agricultural Engineering, Agricultural 

 Research Administration, United States Department of Agriculture 



CONTENTS 



Page 



Introduction 1 



History, host plants, and eco- 



n omic importance 2 



Symptoms 6 



Causal fungus 13 



Isolations of the fungus 13 



Inoculation experiments 15 



Relative susceptibility and resist- 

 ance of host plants in Florida. _ 16 



Page 

 Relation of incidence of the dis- 

 ease to timbered lands and 



soil conditions 18 



Control measures and treatment 



of diseased trees 19 



Summary 22 



Literature cited 24 



^^ ^^»^^^ ^^ ^ ^^ ^ 



INTRODUCTION 



Clitocybe root rot, caused by the fungus Clitocybe tabescens (Fr.) 

 Bres., is a destructive disease of fruit, forest, shade, and ornamental 

 trees, shrubs, and vines, reported to occur from eastern Texas, Okla- 

 homa, Missouri, southern Illinois and Indiana, West Virginia, Vir- 

 ginia, and the District of Columbia southeastward to Florida. 

 Although the causal fungus occurs as far north as New York and 

 Michigan, root rot caused by it has not been reported from the Northern 

 States. 



The root rot caused by 0. tabescens is so similar in its general as- 

 pects to that caused by the closely related root rot fungus Armillaria 

 mettea Fr., that, in the absence of the fruiting bodies or of cultural 

 studies, the diseases caused by these respective fungi may l>e con- 

 fused readily. As a result, the diagnosis of such root rots, particularly 

 in sections where both may occur, may be questionable in some cases. 

 Apparently many cases of mushroom root rot, in the absence of 



1 Much of the work reported here was performed while the writer was em- 

 ployed as pathologist at the Florida Agricultural Experiment Station. 



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