PARASITIC RHIZOCTONIAS IN AMERICA" 



BY GEORGE L. PELTIER, ASSOCIATE IN FLORICULTURAL PATHOLOGY 



INTRODUCTION 



One of the most serious and troublesome diseases which must be 

 contended with by carnation growers in this country is the so-called 

 "stem rot" due to the fungus Rhizoctonia. In 1911 a study of this 

 disease was undertaken at the University of Illinois by Mr. H. W., 

 Anderson, at that time Assistant in Floricultural Pathology and now' 

 Professor of Botany in Wabash College. Since July, 1912, when Mr. 

 Anderson left, a thoro investigation of those diseases of vegetable, 

 field, and floricultural crops which are caused by Rhizoctonia has 

 been conducted by the writer, the primary object being to determine 

 whether infection is brought about by one or by more than one race or 

 species of this fungus. The results of this phase of the work are pre- 

 sented in the following pages. Extensive studies have also been made 

 of stem rot, with a view to publishing at a later date. 



GENERAL HISTORICAL ACCOUNT 



The first description of Rhizoctonia was given by Duhamel, 33 who in 

 1728 found it causing a disease of saffron (Crocus sativus) in southern 

 France. The diseased bulbs were thickly covered with a reddish vio- 

 let network of hyphaa which spread out into the surrounding soil, with 

 knot-like swellings here and there in the mycelial network. Duhamel 

 conceived these swellings (tubercules) to be the individual plants and 

 the hyphse to be the roots, and named the fungus Tuberoides. 



Almost sixty years later (1785) another French investigator, Fou- 

 geroux de Bondaroy, 23 mentioned that asparagus that was grown on 

 land in which diseased saffron bulbs had been previously grown suf- 

 fered from this same disease. Bulliard 11 in 1791 numbered it among 

 the Truffles and named it Tuber parasiticum. Ten years afterward Per- 

 soon 82 placed the fungus in the genus Sclerotium and called it Sclero- 

 tium Crocorum. 



De Candolle, 24 who discovered a similar disease on lucerne, gave to 

 the fungus the name Khizoctonia. Later he distinguished three species, 

 /*. Crocorum, R. Medicaginis, and R. Mali. Nees 70 in 1817 referred 



"The results presented in this bulletin formed part of a thesis submitted by 

 the author to the Graduate School of the University of Illinois in partial fulfil- 

 ment of the requirements for the degree of doctor of philosophy in botany, May, 

 1915. Revised to date of issuance. 



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