115 



half an acre and use the beans from this seed-patch for subsequent plant- 

 ings. By careful selection after this manner each year the disease can be 

 controlled to a profitable extent. 



SUNSCALD OF PEA. 



Ascochyta pisi Libert, on Pisum sativum. 



During the summer of 1907, my attention was called to this disease 

 affecting the garden pea. As observed at this time, the leaves, stems and 

 pods were badly spotted. (Fig. 5.) The spots on the pods were not con- 

 fined to the surface alone, but in many cases extended entirely through 

 the pod, as was evident from the fact that spots were found exactly op- 

 posite those on the other side and the seed between the affected portions 

 was discolored or distinctly spotted by the disease. I gathered a number 

 of the diseased pods of both early and late varieties and planted twenty- 

 three seeds of each variety in the greenhouse during the winter following. 

 Several seeds of the late variety were distinctly spotted. All of the early 

 variety germinated and thirteen of the late variety. Those that did not 

 germinate were found to be decayed. Soon after they came up, nearly all 

 of the plants died. Usually the stem near the base withered and turned 

 brown, resulting in the death of the young plant. 



Five of the forty-six planted lived and produced pods. Even the lower 

 leaves of these withered and dropped off, giving the plant a very straggling 

 appearance. No spots such as were observed on the plants grown in the 

 garden were to be seen, contrary to my expectation, but from the descrip- 

 tion of the disease given by others, 1 the trouble was undoubtedly due to 

 Ascochyta. 



Kruger, a German mycologist, found that if diseased seed was soaked 

 in water from forty-eight to seventy-two hours, the mycelium of the fungus 

 would completely encircle it, and grow out into the water, forming a white 

 mass of radiating threads. Van Hook verified this statement and also found 

 that if the diseased pea seed were placed in a germinator for a few days 

 a heavy coat of white mold would be formed about them in which, if seed 

 were removed to a covered dish with less moisture, numerous reddish- 

 brown pycnidia would be formed. 2 These pycnidia were produced by the 

 mycelium of the fungus which had lain dormant in the seed since its ma- 

 turity. When the conditions were right for the germination of the seed 

 the fungus renewed its growth. The mycelium grows within the stem con- 



1. H. G. Howell, J. M. Van Hook. 



2. Van Hook, J. M., Blighting of Field and Garden Peas. Ohio Bui. 173, 1906. 



