VEGETABLE AND FIELD CROPS 305 



concentric markings. It is known to planters as the brown 

 spot. 



Bed rot, rhizoctoniose (Rhizodonia sp.). — Damping off 

 and rot of seedlings while in the seed bed occur in this 

 disease. The causal fungus may often be seen as spots 

 of web-like white mold upon the ground around the affected 

 plants. The general characters and prophylaxis are dis- 

 cussed under damping off and rhizoctoniose. Seed beds 

 known to be diseased should be avoided unless disinfected 

 before use. 



^ Stem rot {Botrytis longibrachiata Oud.). — In this curing- 

 house disease pure white, velvet-like patches of mold appear 

 upon the stem, spread rapidly to the veins, and cause leaf 

 decay, especially in the regions of the ribs and veins and 

 other parts that dry but slowly. 



The causal fungus matures its spores in great quan- 

 tity upon the refuse stalks and stems, and thus persists 

 from year to year. 



To prevent the disease all refuse should be gathered and 

 burned as soon as the crop is cured, and the floor and barn 

 disinfected with Bordeaux mixture or bluestone. 



Drop, damp off, sclerotiniose {Sclerotinia sp.). — Damp- 

 ing off due to sclerotinia is reported by Clinton* as a 

 common trouble in seed beds. The injury to the plant 

 is similar to that of the usual damping off, p. 60, while 

 the fungus presents the characters described under lettuce 

 sclerotiniose. Young plants are killed; older plants may 

 survive, and if set in the field, develop poorly. 



Polebum, pole rot. — Poleburn is a curing-house disease 

 occurring on hung tobacco. In warm, damp weather the 



' Clinton, G. P., Conn. State Agr. Exp. Sta. Rpt. 1896, p. 326. 

 X 



