ROOT ROT OF THE GRAPEVINE IN MISSOURI CAUSED BY CLITOCYBE TABES GENS (SCOP.) BRES.12 By ARTHUR S. RHOADS Assistant Plant Pathologist, Agricultural Experiment Station of the 'University of Florida; formerly Pathologist, Missouri State Fruit Experiment Station INTRODUCTION Australia and some other countries "white-rot. " According to Verge (Ô6)4 Shortly after the writer had as- the cause of pourridié in Europe is at- sumed his duties at the Missouri tributed to several of the higher fungi, State Fruit Experiment Station in 1922 among them being Armillaria mellea his attention was directed to reports (Fries) Quel., Dematophora necatrix received from several localities of the Hartig, Vibrissea (Roesleria) hypogaea destruction of grapevines caused by Ch. Richon and Le Monnier, and some- root rot. The first opportunity to in- times Psathyrella ampelina Foex and vestigate this disease was afforded by a Viala. In the United States the dis- trip to Knobview, Mo., on May 30, ease has sometimes been attributed to 1922, where, in the vineyard from these fungi and also to Phymatotrichum which the trouble was reported, a (Ozonium) omnivorum (Shear) Duggar. number of vines that had recently died Most American writers, however, have were carefully dug up. All exhibited generally believed that the disease in the same symptoms, namely, an abund- this country is caused by Armillaria ant growth of characteristic whitish to mellea and Dematophora necatrix {51 y isabelline mycelial sheets or mats oc- p. 172-17Jf), although as a rule on as- curring between the layers of the immer sumption rather than from definite bark and between the bark and the evidence. wood of the roots and root crown, oc- Root rot of the grapevine was first casionally accompanied by black rhizo- reported in this country in Missouri, morphic strands. These symptoms in- Scribner (46, p. 137) stating that it dicated that the disease was caused was discovered in a vineyard at Bush- by a mushroom root rot, although no berg, about 25 miles south of St. Louis, fruiting bodies could be found to verify by the eminent French viticulturist the supposition. Cultures and further Viala, in 1887, while the two were field studies were made which afforded making a tour of the principal grape- a basis for the conclusions herein growing regions of the United States. reported.3 The same author also states (Jft, p. 12; 48, p. 64) that they found the disease HISTORICAL REVIEW later in northeastern Texas and again in Napa Valley, Calif. He records the Although grapevines are known to be fact that he has seen a number of vines attacked by several different root rot- nearly or quite dead from the same ting fungi, especially when the root disease in the vicinity of Knoxville, systems have become weakened or in- Tenn. jured, comparatively few investigations In 1892 Pierce (38 p., 153-161), dis- have been made in this country of cussing the relation of root-attacking the resulting diseases. fungi to the California vine disease, Root rot of the grapevine has long states that Dematophora, although been known in Europe, where it has found in several places in the United been investigated extensively. In States, had not been seen in California; France it is called "blanc des racines" that Armillaria mellea has been re- or, more commonly, "pourridié;" in ported in northern California; and Germany " Weinstock-fäule;" and in that Vibrissea hypogaea was found in i Received for publication May 19, 1924; issued April, 1925. 2 Commonly known in this country under the names Clitocybe monadelpha (Morg.) Sacc, Armillaria mellea exannulata Peck, Clitocybe parasítica Wilcox, and Monadelphus caespitosus (Berk.) Murrill. 3 The writer gratefully acknowledges helpful advice and suggestions concerning the taxonomic treat- ment of the fungus under discussion from Dr. E. A. Burt of the Missouri Botanical Garden, Dr. L. O. Overholts of the Pennsylvania State College, and C. G. Lloyd of the Lloyd Library and Museum at Cincinnati. Grateful acknowledgment is made of the invaluable services rendered by the libraries of the Missouri Botanical Garden and the U. S. Department of Agriculture. 4 Reference is made by number (italic) to "Literature cited," p. 364. Journal of Agricultural Research, Vol. XXX, No. 4 Washington, D. C. Feb. 15, 1925 Key No. Fla.-2 (341) 342 Journal oj Agricultural Research Vol. XXX, No. 4 the Santa Ana Valley on the roots of that all of these were affected by root vines which had been brought from rot, they believe that the greater part Missouri. He also reports the oc- of them died from this cause. These currence of a species of Graphium in- authors conclude that the Herbemont festing diseased vine roots in the and Rulander varieties are immune Santa Ana Valley but thinks that it and that the Delaware is very resistant bore no relation to the cause of the to mortalitv from root rot. disease in question. In 190r Wilcox (58) described a Between this date and 1900 a few rhizomorphic root rot of fruit trees additional reports were made of grape- which was causing widespread destruc- vine root rot. McCarthy {251 p. 122), tion of orchards in Oklahoma and ad- discussing the disease in North Caro- jacent States. He demonstrates that lina, and Starnes (50, p. 282), in this disease is caused by a species of Georgia, both arbitrarily attribute it Clitocybe, which he describes as a new to Dematophora necatrix and Armillaria species, Clitocybe parasitica. In addi- (Agaricus) mellea, merely because the tion to its occurrence on fruit trees, he same disease in Europe was commonly finds the fungus to be a common para- attributed to attacks by these fungi. sitic and saprophytic form on four species of oaks in Oklahoma. A rhizo- Underwood and Earle "(54, p. 272), T discussing root rot of the grapevine in morphic root rot, w hich Wilcox as- Alabama, state that it seems to be sumes was caused by this species of identical with the disease known as Clitocybe, is reported as occurring also "pourridié" in France. They believe in Texas, Missouri, southern Illinois, that it is quite prevalent and often Indiana, and to some extent in Ohio, does serious damage, as evidence of Georgia, California, and Oregon. Ex- which they mention the fact that out cept for a few references in the bibli- of the 584 vines in the station vineyard ography appended, Wilcox makes no all but 83 showed evident signs of the mention whatever of this disease on disease, and that many died during the the grapevine, which, in some cases, late summer and fall. They note that undoubtedly is caused by the same fun- the character of the soil apparently has gus as that with which he was working. much to do with the prevalence of the Walker (57, p. 30) and Hewitt and disease, that vines may live many years Hayhurst (21, p. 424) reported that while more or less affected by it, and root rot of fruit trees is widespread in that some varieties are evidently much Arkansas and causes serious damage more resistant than others. Earle in some localities. The first author and Austin (Í4), writing four years says that, "besides the apple it affects later, give a much more detailed ac- probably all of the commonly culti- count of grapevine root rot in Alabama vated fruit trees, the grape as well as a and question the earlier statement of number of forest trees," and states that Underwood and Earle (54, V- 272) the disease is caused by toadstool that this disease is the same as the fungi, "two of the forms concerned be- "pourridié" of the French, which they ing Clitocybe parasitica and Armillaria say is caused by Dematophora necatrix. mellea." Repeated attempts to isolate and Duggar (13, p. 471) mentioned the culture the organism causing the abundant occurrence of Clitocybe para- whitish mycelial growth under the bark sitica at Columbia, Mo., during favor- of diseased roots were unsuccessful able seasons on roots of hickory and and further observations led Earle other deciduous trees, but failed to and Austin to conclude that the dis- observe its occurrence in orchards, ease works much more slowly than the despite special effort to find it. The European root rot. These authors suggestion by some observers that state that the mycelial whitening can Armillaria mellea is responsible for often be found on old Scuppernong the root rot of fruit trees attributed to vines and on wild grapevines in the Clitocybe parasitica is refuted by Dug- woods, although these are seldom if gar, who states that he has never ever killed by it, and that its presence detected this fungus associated with on the roots of cultivated vines is by the typical disease in Missouri. Al- no means a sure sign of immediate though Armillaria mellea may occur in death. From an examination of the Missouri, and in this case be responsi- statistics on grape planting at the ble for some of the root rot reported, Alabama station these authors con- the writer has never seen it in the State clude that the disease is a very serious even in forests where in favorable sea- one. They state that of the 651 vines sons Clitocybe parasitica often abounds. alive or planted in 1894, a loss of 483, Butler (8, p. 24-29), in his account of or 75 per cent, was sustained in six root rot of grapevines in California, years and, although there was no proof describes a slow and a rapid form of Peb. is, 1925 Root Rot of Grapevine Caused by Olitocybe Tabescens 343 the disease, but contributes nothing to its greatest development in the medul^ the identity of the causal organisms lary rays, probably by reason of the involved.