CLITOCYBE ROOT ROT OF WOODY PLANTS 5 



Plakidas reported a crown girdle of sand pear (IS) and tung trees 

 (16) in Louisiana, with which . tdbescens was later determined to be 

 associated, along with Dothiorella (Botryosphaeria) and sometimes 

 other fungi. Clitocybe root rot was reported subsequently by Hines 

 (11), Bain (2), Large (13), and the writer (24) as causing losses of 

 trees in tung tree orchards in one or more of the following States : 

 Louisiana, Mississippi, and Florida. 



In Opelika, Ala., in July 1941, the writer observed two dead Lom- 

 bardy poplars (Populus nigra var. italica) , a nearly dead silver maple 

 (Acer saccharinum) , and a dying pomegranate (Pwnica granatum) , 

 all attacked by Clitocybe root rot. On the grounds of the experiment 

 station at Auburn, Ala., where a number of peach trees had died a short 

 time before from a trouble thought to be waterlogging of the clay 

 soil, a peach tree (Prunus persica) and a wilting American plum 

 (Prunus americana) also were found dying from this root rot. G. 

 tdbescens was isolated from the roots of each of these trees. Under- 

 wood and Earle (31) in 1896 and Earle and Austin (6) in 1900 re- 

 ported a heavy mortality of grapes on the Alabama station grounds 

 from a root rot of undetermined cause characterized by a whitish 

 mycelial growth under the bark. Earle and Austin (6) stated that, of 

 the 651 vines alive or planted in 1894, 483, or 75 percent, were dead by 

 1900. 



The economic importance of Clitocybe root rot varies greatly, ac- 

 cording to the prevalence of the fungus in local areas, the age and 

 extent of the planting, its esthetic or commercial value, and the sus- 

 ceptibility of the host species to the disease. Losses on numerous 

 properties examined in Florida have varied from an occasional tree or 

 shrub to serious losses continuing over a period of several years ; the 

 loss of scattered trees or groups of trees in commercial plantings of 

 citrus, peach, and tung; or the loss of a majority of the trees in 

 windbreak or roadside plantings of the highly susceptible Australian 

 pine 3 or beef wood ( Casuarina spp. ) . The occasional loss of a plant in 

 a yard rarely causes much concern unless it is a particularly prized 

 specimen. However, on properties where dying of plants continues 

 over a period of years, losses may be extensive. When such losses 

 occur on a large number of properties in Florida alone, it is evident 

 that the aggregate losses in ornamental plantings become of consider- 

 able importance. Occasional properties in various parts of Florida 

 have been found to be veritable hotbeds of infection for the Clitocybe 

 fungus, with trees and shrubs thereon dying at frequent intervals 

 over a period of several years. Properties at points in Florida where 

 this fungus has been unusually destructive invariably have been ham- 

 mock, pine-oak, or scrub oak types of land on which various species of 

 oaks grew abundantly prior to clearing. 



The writer has reported Clitocybe root rot in Florida on bananas 

 (#1), citrus (27), Australian pines (28), tung tree (24), and miscella- 

 neous forest trees, fruit trees and ornamental trees, shrubs, and vines 

 (23). At a Florida nursery a %-acre planting of closely set stock 

 plants of both the India-rubber fig (Ficus elastica) and the variety 

 variegata was being grown under a lath shed for commercial propaga- 



3 Although these trees are often called beefwood, the name Australian pine, by 

 which they are generally known in Florida will be used in this circular. They 

 are hardwoods, however, not pines. 



