114 



the mycelium remains in a more or less dormant state until conditions art* 

 favorable for the germination of the bean seed, when it renews its activity. 



An examination of a diseased seed will reveal an abundance of my- 

 celium in the infected portions. By carefully treating the seed with hot 

 water or formalin to rid them of surface fungi and placing them in a 

 sterile moist chamber, one is able to obtain spores in great profusion on 

 the seed before it has germinated and later on the cotyledons, stems and 

 leaves of the seedling in the sunken and discolored cankers caused by the 

 fungus. Dr. Halstead reports that he has found spores of the Anthracnose 

 on the dry beans, especially in the cavity between the cotyledons. 1 



In the germinating plant, no doubt the plumule is often infected by 

 contact with the diseased portions of the cotyledons. (Fig. 3.) Spores, 

 however, are produced upon the cotyledons after the bean has expanded 

 its true leaves and when released by the dissolution of the mucilaginous 

 matrix they are washed to the ground or on the stems below. The stems 

 become infected from these spores and cankers are formed at the infected 

 places. Often these cankers encircle the stem and thus cut off the supply 

 for the leaves above. Sixty-one German Wax Beans apparently healthy 

 were planted in the greenhouse. When well up five were observed which 

 had infected cotyledons, the others appearing healthy. Seventeen days 

 after planting thirty-one of the plants were affected by the disease at the 

 base of their stems, showing, doubtless, that spores from the cotyledons 

 of the five plants had infected the stems of the others. (Fig. 4.) 



When the plants are moist the spores of the fungus are in a condition 

 to be easily disseminated, so that working among the plants at this time or 

 otherwise disturbing them aids in the dissemination of the fungus if any 

 diseased plants are present. Even the wind aids dissemination by scatter- 

 ing contaminated drops of water to healthy plants, or by blowing the plants 

 against each other. In this way the disease spreads to the leaves, stems 

 and pods of the plant during the growing season. 



The selection of seed from unaffected pods seems at present to be the 

 most satisfactory method to pursue in controlling the disease. The pods 

 should be selected in the field and only such as are perfectly free from all 

 evidence of disease should be selected. Apparently healthy beans within an 

 infected pod may harbor the mycelium of the fungus without showing any 

 evidence of it. Enough seed can be selected in this way to plant small 

 patches. Those who grow large areas should select enough beans to plant 



1. Halstead, B. D., The Anthracnose of the Bean. A Remedy Suggested. Ann. 

 Rept. N. J. Agr. Exp. Sta. 1891, p. 284. 



