EXPERIMENT STATION BULLETINS. 665 



lower part of the leaf with relatively the same number of spores in each 

 inoculation. G. Kock does not mention his method in arriving at his 

 conclusions. This, of course, precludes the possibility of comparison of 

 results. Judging from his article he relied merely on field appearances. 

 It is interesting to contrast the following observations by J. B. S. Nor- 

 ton (1914) : "Practically all the varieties grown in America and Europe 

 have been tried here the past two years, and all showed about the same 

 amount of Septoria Blight on the foliage. Some varieties are, however, 

 more vigorous growers and continually keep ahead of the blight by the 

 production of new foliage." 



Here as in all work on resistance and immunity in reference to plant 

 disease, the whole matter of resistance and susceptibility is obscured by 

 disease Tole>-cmce mid Escape. (Orton, 1908; Freeman, 1911). We might 

 add to this the ability to repair or replace damaged tissue. In view of 

 the total lack of any superiority of any one variety in the experiments 

 reported, the writer feels that the explanation of Norton is correct and 

 the rapidity of growth of some varieties (as contrasted with the slow- 

 ness of the dwarfs) is responsible for the apparent cases of resistance 

 to disease of certain varieties of the tomato, Lycopersicon lycopersicon. 



RECOMMENDATIONS FOR CONTROL MEASURES. 



Before control measures can be considered, we must recognize the fal- 

 lowing observations that have been dealt with above: 



1. The sources of infection are at least two: the greenhouse or the 

 hotbed and the old trash in the field. 



2. Infection results from inoculation upon the upper and lower sur- 

 faces of the leaf. 



3. The period from the time of inoculation to spore exudation is 

 about 13 days. 



4. Moisture is the primary agent in dissemination of the disease. 



5. The exudate of spores is in the form of a mucilaginous mass. The 

 spores are always transferred by some external agency. 



6. It has been shown that the mycelium will not grow at 371/2° F., 

 (98° C.) and will not revive after ten days at this temperature. Since 

 this temperature is frequently reached during the summer months, this 

 must be taken into consideration as a natural means of checking the dis- 

 ease. 



The most important control measures for this disease are prophylactic. 

 Clean seedlings in clean soil, if reasonably isolated remain practically 

 free from the disease. 



In order to be sure that the seedlings do not become diseased at the 

 start, clean soil should be used in the greenhouses devoted to seedling 

 production. The soil should be fresh or sterilized. The seedlings should 

 be sprayed as soon as their height above ground makes it practicable, and 

 again before being transplanted to the field. For this a weak Bordeaux 

 mixture (2-2-50) is advised. 



Since it has been determined that wintered-over, diseased vines possess 

 spores which are viable, the old trash must be destroyed as far as pos- 

 sible. Since, however, this is not practical except in greenhouses and 



