PARASITIC RHIZOCTONIAS IN AMERICA 317 



eliiip of the outside tissues and a browning of the leaves. However, 

 the plants so affected did not wilt down entirely, and many of them 

 recovered. 



CANDYTUFT, Iberis sp. 



During June, 1914, a few plants of candytuft that had been grow- 

 ing in three-inch pots in the floricultural greenhouses, rotted off at the 

 surface of the ground. The symptoms were similar to those described 

 for sweet alyssum. Microscopic examination of diseased tissue re- 

 vealed R. Solani in every case. Dense masses of hyphge covering the 

 leaves and stems of these plants were plainly visible. 



Duggar and Stewart 32 in 1901 reported damping-off by Rhizoctonia 

 of cuttings of candytuft in New York. 



CARNATION, Dianthus caryophyllus 



Khizoctonia Solani attacks carnation plants of all ages, both in the 

 field and in the greenhouse, causing not only stem rot, but damping- 

 off of cuttings, of which it is one of the principal causes. 



The symptoms of stem rot of carnation are very characteristic of 

 the effects of R. Solani (Fig. 1). The fungus usually attacks the 

 stem of the plant at the surface of the ground or occasionally just 

 above or below. As a rule, the first indication of the disease is a pale 

 green color of an entire plant or of a single branch. This lighter color 

 can be noticed in most cases for several days before the actual wilting 

 takes place. During cloudy weather the plant does not wilt for two 

 weeks and sometimes for even longer, altho the stem may be almost 

 completely rotted ; in sunny weather wilting occurs much sooner. 



If the stem of a plant that shows the first sign of wilting is pressed 

 just at the surface of the soil, a soft place is felt and a slight twist is 

 sufficient to slough off the bark. Beneath this is a slimy, wet area, 

 which gives this rot its characteristic name. Sometimes, however, the 

 stem is dry at the point of attack, and upon being broken off, the fibers 

 appear to be separated and stringy. 



The fungus enters the cracks in the corky layer of the bark and at- 

 tacks the cambium layer, causing the sloughing off of the bark. It 

 then penetrates the woody tissues, and can be found even in the pith. 

 The plant may remain alive after the cambium layer is destroyed until 

 the fungus plugs the vessels. If a diseased plant is left in the soil for 

 some time, the mycelium overruns the stem, and dark, round sclerotia 

 are formed either directly on the bark or in the crevices, or cracks. 



The Rhizoctonia disease of carnation has been known to florists 

 ever since carnations have been grown as a commercial crop in the 

 greenhouse. In Volume I of the American Florist, 1886, is found the 

 following paragraph, which is probably the first published statement 

 concerning the stem rot of carnation in this country. 



' ' In a few days plants began to show signs of wilting, and upon examination 

 I found them rotted off just at the top of the ground, tho half an inch under 

 the ground the stems appeared perfectly healthy." 



