204 



DISEASES OF ECONOMIC PLANTS 



Round Pod Wax, Refugee Wax, Burpee's White Wax, 

 Grenell's Rust-proof Ciolden Wax, Wardwell's Kidney Wax, 

 Dwarf German Blacli Wax, Early Valentine.' 



Stem rot, pod rot {Rhizodonia sp.). — This disease is 

 manifest in three forms : ^ — 



1. Damping off of seedlings. See damping off. 



2. Dry rot of the stem. In this condition the tissue is 

 dead, discolored, and dry-rotted at from 2-5 cm. above the 



-T '^t«* 



Fig. 92. — Bacterial disease upon bean seeds. After Clinton. 



ground. The rot extends to the pith and usually encircles 

 the stem, and thus so weakens the plants that they are 

 often broken by the vnnd. In any event they soon wilt 

 and die. 



3. As brown sunken areas upon pods, penetrating to 

 and discoloring the seeds. The germination of the seed is 

 not stopped by this attack, and a fruitful source of dissemi- 

 nation is thus afforded. Such seeds should be avoided.^ 



Downy mildew (Phytophthora Phaseoli Thaxt.). — The 

 downy mildew is a northern disease regarded l)y Halsted'' 



' Duggar, B. M., and Stewart, F. C, N.Y. {Cornell) Agr. Exp. Sta. 

 Bui. 186, January, 1901. 



^ Fulton, H. R., La. Agr. Exp. Sta. Bui. 101, Januarj', 1908. 

 ' Hedgcock, G. G., Sci. n. o. 1.9, 208, February, 1904. 

 « Halsted, B. D., N.,I. Agr. Exp. Sta. Bui. 151. 



