168 Mortier F. Barrus 



Sorting out affected seed 



The selection of clean seed has been recommended by many plant 

 pathologists. Frank (1883b: 523), after having determined that infection 

 of the seedling can take place from the fungus overwintered in affected 

 seed, was the first person to recommend the use of clean seed by the 

 sorting-out of spotted ones or by the securing of seed from non-infested 

 fields. Beach (1892:323-326) obtained good results by sorting out the 

 affected seed before planting. Gain (1898:200), after experimenting 

 with Mont d'Or, a climbing wax-podded variety with dark brown seeds, 

 states that he is able to discard practically every diseased seed by 

 hand-sorting. He observes that diseased seeds are lighter than healthy 

 ones, and advises growers to discard all light seed. In another article 

 (1899:389) he says that by carefully sorting out infected seed the anthrac- 

 nose disease can be controlled. Whetzel (1908:432), however, although 

 he used the utmost care to remove every suspected bean, was unable to 

 remove the diseased seed completely from white beans, a germination 

 test of the seed thus sorted showing as many as 12 per cent of the remaining 

 seed diseased. When an attempt is made to sort colored seed, an even 

 larger percentage of diseased seed passes unobserved. Fischer (1919:252) 

 concludes from experiments conducted by Schander and Krause, and 

 from other tests made at Bromberg in 1915 and 1916, that it is not possible 

 to control the disease by this method since many affected seeds cannot 

 be detected from their appearance. 



It is, of course, impossible to sort out every affected seed even by the 

 most careful examination. Such seed as are left in may produce affected 

 plants if conditions following planting are favorable for the development 

 of the fungus, and such affected plants may serve as a source of inoculum 

 to other plants in the field. However, as every diseased seed discarded 

 removes one source from the field, it would appear to be preferable to 

 sort the seed carefully before planting rather than not to sort at all. A 

 practical grower of a considerable acreage of beans in northern Vermont 

 says that since he has made a prac.tice of hand-sorting his seed he has 

 had no anthracnose, but that before he did so the disease was harmful. 



Selecting seed from clean pods 



It has occurred to a number of experimenters that the surest way of 

 obtaining clean seed is to select it from healthy plants or at least from 



