SWEET PEA DISEASES AND THEIR CONTROL 141 



1910, carried out inoculation work with the supposed parasite, viz., 

 Thiclavia basicola, obtaining during the first two seasons negative 

 results. In this work Chittenden gives a good description of the 

 disease. He found in 1910 that by excessive watering he was able 

 to get infections from Thielavia, but he does not indicate they were 

 the typical "streak." He writes in conclusion, "To sum up, as 

 far as our experiments go, the ' streak ' disease is brought about by 

 the attack of the fungus Thielavia basicola on plants that have re- 

 ceived some check at the root." 



Symptoms of the Disease. Like the Bacteriosis of beans, streak 

 makes its appearance in the season of heavy dew. On the sweet 

 pea the disease usually appears just as the plants begin to blossom ; 

 it is manifested by light reddish-brown to dark brown spots and 

 streaks (the older almost purple) along the stems, having their 

 origin usually near the ground, indicating distribution by spattering 

 rain and infection through the stomata. The disease becomes 

 quickly distributed over the more mature stems until the cambium 

 and deeper tissues are destroyed in continuous areas, when the 

 plant prematurely dies. Occasionally petioles and leaves show 

 infection; the latter show the usual water-soaked spots common to 

 the bacterial leaf blight of beans. 



The disease is not a vascular infection; it confines its attack to 

 the mesophyll, the cambium and deeper parenchymous tissues. 

 The lesions on the stems gradually enlarge and deepen till they 

 come together. 



The disease is severe on Soy beans, in which the lower lesions 

 girdle the stem and penetrate so deeply that the plants blow over, 

 as is occasionally to be met with in the "black leg" of potatoes 

 (a bacterial disease). 



In young clover in August and September it is particularly in- 

 jurious, vying with Bains' Anthracnose (Colletotrichum trifolii 

 Bain) and the clover root borer in its activity. In clover of all 

 ages, probably the most severe attack takes place in the petiole at 

 its union with the stem; in which case the entire leaf dies and the 

 lesion extends down into the stem. The blackening of the stems 

 and the spotting and water-soaking of areas on the leaves are 

 common with the clovers. 



