CEPHALOSPORIUM WILT OF ELMS 5 



foliage or "flags" in the crown is usually the first sign of the presence of the disease. 

 Later the leaves die, turn brown, and roll in from the margins toward the upper 

 surface of the leaf. The death of the twigs is evidenced by drooping, drying out, 

 and a tendency of the terminal leaves to persist for some time. Usually these 

 symptoms appear first in a small section of the crown and gradually enlarge as the 

 disease spreads from the smaller branches to the larger. The disease in Massa- 

 chusetts has been found to advance progressively over a period of years. This 

 is in agreement with Liming's statement that affected elms show an increase in 

 the diseased condition the second year of observation. Goss and Frink (11) 

 describe the yellowing as beginning at the base of the leaf and gradually spread- 

 ing up along the midrib, then out along the veins to the margins; this being fol- 

 lowed by the browning of the tissues and the death of the leaves from the margins 

 inward. 



The internal symptoms usually precede the external; a streaking of the wood 

 in affected twigs, particularly in the spring wood, is a characteristic of the former 

 (Fig. 3). The streaks are brown and may be more pronounced than those as- 

 sociated with Ceratostomdla iilmi (Schwarz) Buisman. However, as no distin- 

 guishing characteristics for the accurate field identification of diseases affecting 

 the vascular tissues of elms are known, only the isolation of a fungus known to be 

 associated with the discoloration in elm wood can determine whether a fungus 

 disease is present. In trees where the disease is well established the discoloration 

 often forms a solid ring, but w^here the disease is less serious the streaking may be 

 confined to one side of the twig or may form a discontinuous ring in the spring 

 wood. 



Figure 3. Diseased Elm Twigs, showing cliaracterislic discoloration in tiie spring wood. 



LABORATORY STUDIES 

 The Fungus 



The morphology of the genus Cephalosporium is described by Buchanan (7) 

 as being characterized by its well-developed hyaline mycelium and its slender, 

 unbranched conidiophores in which nonseptate spores are abstricted from the 

 tip. These spores are pushed to one side by the development of additional spores. 

 The spores produced in this manner from the tip of a condiophore are stuck 

 together by mucus and thus remain as a head. 



The mycelium is much branched and septate, and is hxaline in all cases, at 

 least when young. The sterile hyphae are of indeterminate length. The diame- 

 ters of the hyphae vary from 5 to 25 microns. The cell contents, at first homo- 

 geneous, become somewhat vacuolate and later hold a large number of oil drops. 

 The hyphae cross and recross repeatedly; they penetrate the medium to a depth 

 of half an inch in agar. The organism grows well only in the presence of an 

 abundance of ox>gen. 



