DISEASES OF FLOWERING PLANTS 211 



231. Fairy-ring spot on carnations. Classification: Hypho- 

 mycetes, Dematiese ; Heterosporium echinulatum Berk. Fairy- 

 ring spot on carnations is quite prevalent in some sections, the 

 disease attacking the leaves, stems and sepals of the flower. 

 Light-colored spots appear on affected tissue and on these are 

 formed concentric rings of dark-colored, spore-bearing bodies. 

 The spores are usually four-celled and from each cell an infect- 

 ing germ-tube develops. A second row of spore-bearing bodies 

 develops in a concentric ring around the first, and this continues 

 indefinitely, giving to the fungus the common name of fairy- 

 ring. 



232. Branch-rot of carnations. Classification: Tubercu- 

 larieae ; Fusarium, species. Branch-rot is frequent on carna- 

 tions, attacking the larger branches and sometimes the main 

 stem. When the disease gains a foothold, the stems gradually 

 wilt and the foliage turns a yellow green. The stem tissue 

 becomes dry and firm, even after the death of the plant has 

 resulted. It may attack the host at any time, and is frequent 

 in the cutting bench. 



233. Microscopical nature. The spindle-shaped and sickle- 

 like spores of this fungus are produced in quantities on the 

 mycelium of the plant. When they fall on plant tissue where 

 the epidermis is injured, they quickly germinate. An infecting 

 mycelium penetrates the interior tissue of the stem, and absorbs 

 the protoplasmic cell contents. This causes the tissue to become 

 shrunken, the vital processes of the plant are checked and star- 

 vation results. 



234. Preventives. As branch-rot commonly attacks cut- 

 tings, conditions in the propagating house should be such that 

 the development of the disease will be checked. It is consid- 

 ered wise to avoid shortening the terminal growth when cuttings 

 are made, for this injury to the leaf tissue permits the pathogen 

 to gain an entrance to the interior of the stem. Sand in the 

 cutting benches should be changed frequently and everything 

 possible done to encourage a rapid rooting and a healthy devel- 

 opment of the cutting. Take cuttings only from healthy stock, 

 and use great care in re-potting and in field planting. This 

 assists in keeping the plants free from branch-rot. 



235. Remedies. So far as known, there are no remedies. 

 If the disease gains a foothold in the benches, all affected plants 

 should be removed and replaced by healthy, disease-resisting 

 varieties. 



