134 MASSACHUSETTS HORTICULTURAL SOCIETY 



Thielavia root ROT, Thielavid hasicola Zopf . 



Chittenden ^ and Massee ^ have suspected the fungus Thielavia 

 basicola to be the cause of " Streak." This latter disease, Manns 

 and Taubenhaus ^ have shown to be of bacterial origin, and related 

 to a bacterial disease of the clovers. Plants severely infected with 

 Thielavia have practically little or no root system, since the latter 

 is destroyed by the fungus as rapidly as the roots appear. What- 

 ever root system be present is of a stubby nature, charred in appear- 

 ance. The fungus sometimes works up on the stem to a distance 

 of 2 to 3 inches above ground, but never to the extent of invading 

 the entire stem. It is probably due to this blackened appearance 

 of the roots and of the stem nearest the ground that some workers 

 have mistaken this disease for the well-known "Streak" disease. 

 Chittenden, in his report to the National Sweet Pea Society of 

 England, gives an accurate description of the "Streak," so that 

 there caji be no doubt but that he had the disease well in mind, 

 that is, he described it as a stem disease. The Thielavia disease, 

 as already mentioned, is not a stem but a root disease. 



Chittenden seemed to have been unable to infect healthy sweet 

 pea seedlings with the fungus Thielavia basicola under normal 

 conditions of growth. It was only when his plants were subjected 

 to over-watering that the fungus became an active parasite. In 

 our inoculation experiments, healthy sweet pea seedlings have been 

 readily infected by placing the Thielavia fungus on the roots of 

 plants growing in sterile soil. In two to three weeks the roots 

 were thoroughly diseased. Over-watering was not found necessary 

 to bring about infection, although such treatment as well as injury 

 to the roots favors the fungus in its activity. 



The fungus Thielavia basicola is a very common source of seed- 

 bed trouble in tobacco and trucking districts in the United States. 

 Plants infected with Thielavia basicola do not quickly die; they 



1 Chittenden, F. J. Diseases of the sweet pea. Sweet Pea Annual: 14-24, 1912. 

 England. 



» Massee, George. A disease of sweet peas, asters and other plants — Thielavia basicola 

 Zopf. Roy. Bot. Garden. Kew. Bui.: 44-52, 1912. 



' Manns, T. F. and Taubenhaus, J. J. Streak, a bacterial disease of the sweet pea and 

 clovers. Card. Chron. (London): 215-2t6, 1913. 



