Some Diseases of Beans. 



297 



water heated to 122° F., while dry beans can endure such a temperature 

 for some time without injury. While this gives some promise of success 

 the treatment is open to many of the objections raised in the case of the 

 anthracnose (See page 291). 



Selection of clean seed.— The sorting of seed affected with anthrac- 

 nose has been shown to be highly desirable. Its value in the case of seed 

 affected with blight is very questionable. Owing to the fact that blight- 

 aft'ected seeds are often not discolored, it is manifestly impossible to sort 

 them from the healthy ones. The safest method is to discard all seed 

 known to have come from fields that showed the disease. 



Destnicfioii of diseased tops; rotation. — In regard to these practices 

 Professor. Barlow says, "A field where beans have sickened with this dis- 

 ease is unfit for growing beans for at least one season, as the germ lives 

 over at least one winter in the stems and leaves left on the ground. How 

 long such a field may re- 

 main infected is un- 

 known, for we do not 

 A-et know whether the 



Mqceliutn 



'"Kj 



germ can live and in- 

 crease in the soil where 

 no beans are growing, 

 although this is probable. 

 Bean straw from in- 

 fected fields may be 

 burned. If it is fed to 

 animals or itsed in bed- 

 ding, the manure shotild 

 be returned to the field 

 on which the beans grew, 

 and not spread on fields 

 as yet free from the cFis- 

 ease." 



S p r a y i n g. — At the 

 New Jersey Experiment 

 Station, Dr. Halsted has 

 experimented for a num- 

 ber of years with several 

 spray mixtures for the 

 prevention of bean 

 blight. The Bordeaux 

 mixture of the strength 

 recommended for the anthracnose has been found to be very satisfactory. 

 Probably a larger number of applications will be necessary for the blight 

 than for the anthracnose. 



Leaf Tissue 



Fig. 114. — Diagrammatic section across a bean leaf af- 

 fected with "summer stage" of the "Rust." The spores 

 are formed on the ends of the mycelial threads, just 

 beneath the epidermis ivhich is pushed up and 

 broken. The light brown summer spores are ihin- 

 walled and warted. The mycelium- grows through 

 the leaf tissues between the cells which become 

 shrunken and distorted, and so unable to do their 

 work properly. 



