286 Bl-lletin 255. 



there is taken into consideration the loss of seed resulting from such 

 treatment; in the second place, as pointed out in the bulletin under 

 discussion page 206, "The mycelium of the fttngus is imbedded in the 

 bean itself, and any poison that will penetrate sufficiently to kill the fungus 

 will usually kill the seed." In other words, the nature of the bean 

 Anthracnose disease is such that treatment with poisons cannot be 

 effective, since they cannot reach the parasite within the tissues of 

 the host without also destroying the host itself. In the case of oat 

 smut, for example, the spore of the parasitic fungus, which causes the 

 disease, is on the outside of the kernel where it may be readily reached 

 by a poisonous solution. On the other hand, in the case of loose 

 smut of wheat we have a condition analogous to the bean anthracnose. 

 Here the fungus enters the young seed, penetrating deeply into the flesh. 

 It has been found that seed treatment with formalin, for example, 

 which is effective for the oat smut, is entirely ineffective in the case of 

 the loose smut of wheat, and for this reason the analogous case of the 

 bean anthracnose may hardly be expected to be exceptional. 



Selection of clean seed. — On page 206, it is recommended that all 

 beans should be carefully handpicked in order to remove the diseased 

 seed. Many growers do this regularly in order to obtain a good stand, 

 for by hand-picking they remove wrinkled and broken seed. It has 

 also been believed that we might thus eradicate the anthracnose. 

 Careful germination tests conducted during the winter of 1907, showed 

 beyond doubt that the anthracnose could not be eradicated in this 

 manner. In the case of White Beans, a certain amount of the anthrac- 

 nose may undoubtedly be gotten rid of in this way, but even here the 

 writer, though using the utmost care to remove every suspicious looking 

 bean, was unable to remove completely the diseased seed, for upon making 

 germination test of the seed thus sorted, as much as 12 per cent, was found 

 to still show the disease. In the case of black or colored beans, sorting to 

 remove anthracnosed seed was entirely ineffective. One grower who 

 had been to considerable expense in hand picking his beans, which were 

 of the Refugee variety, sent samples to the writer both of the clean beans 

 and the culls. Repeated germination tests from these samples, showed 

 that on the average as many diseased seed had gotten into the presumably 

 clean beans, as had been cast out in the culls. In other words, the 

 grower had thrown away a very large per cent, of his seed, and that too 

 at a considerable expense. From these observations the writer is forced 

 to the conclusion that the hand-picking of beans to eradicate or even par- 

 tially control the pod-spot is of no value, and is therefore not to be recom- 

 mended. 



