EXPERIMENTS IN FORCING AND CROSSING TOMATOES. 



669 



attacks the fruit. Fruit-rot appeared on some of the 

 plants, but it was apparently the same as that which 

 attacks outdoor plantations. 



It soon appeared probable that the disease is bacterial 

 in origin, and it was at first thought that it is identical 

 with the bacterial potato-blight, and that our plants had 

 originally contracted the disease from soil taken from an 

 infested potato-field; butT. J. Burrill, of the University of 

 Illinois, holds that the trouble is probably not the same 

 as the potato-disease. It was then 

 thought that the disease might be 

 identical with the southern toma- 

 to-blight described by B. D. Hal- 

 sted in Bulletin 19 of the Mis- 

 sissippi experiment station. Spec- 

 imens were sent him, and it was 

 found that the two are distinct, 

 both in external appearance and 

 in the character of the organism, 

 the germ of the southern blight 

 being a bacterium, while this is 

 a micrococcus. 



Professor W. R. Dudley, who 

 has made some preliminary exam- 

 inations of the diseased plants, 

 says : "I find a species of micro- 

 coccus present in limited numbers 

 in the cells of tomato-leaves ; in 

 those which were blanched, indi- 

 cating the earlier stages of this 

 disease, in those blackened by its 

 later development, and also in 

 the diseased fruits. Moreover, the 

 external aspect of this disease — 

 the blackening or blighting of 

 portions of the plants — is such as 

 characterizes diseases occasioned 

 by bacteria in other plants. 

 Nevertheless, the preliminary cul- 

 tures made did not give any re- 

 sults supporting this theory. 



"From microscopic examina 

 tion of a considerable number of 

 leaves from various sources, and 

 observations in relation to this 

 disease, on winter-grown tomatoes 

 elsewhere, I think that no injuri- 

 ous effects of bacteria will appear, 

 if houses are kept clean, properly 

 heated and ventilated, so that the 



vitality of the plants will not be impaired, and also if 

 the houses are renovated at intervals." 



Various treatments have been tried upon this disease. 

 Our first attempt was thorough spraying with ammoni- 

 acal carbonate of copper, but our efforts, although care- 

 fully made at intervals, were unsuccessful. It was 

 then thought that treatment of the soil in which new plants 

 were set might be effective, and as our crop was grown 



All our experiments, however, simply lead us to the 

 conclusion that the best treatment for this winter blight 

 is to remove all diseased plants at once, and if it becomes 

 serious, to remove all the plants and soil in the house and 

 start anew. They emphasize, also, the great importance 

 of starting with new plants and fresh soil every fall. And 

 all our experience thus far has shown that the disease 

 is fatal to success in tomato-forcing, for we lost our crop 

 in an endeavor to treat it. 



in boxes- 



FiG. 2.— The Winter Blight. (A healthy plant in front.) 



2. Common Blight {Cladosporiian fulvuni). — The 

 blight oftenest associated with the forcing of tomatoes 

 appears as cinnamon-brown spots on the under surfaces 

 of the leaves, as indicated by the dot-shaped portions of 

 the leaflet in fig. 3. Fortunately, this fungus is rarely 

 serious. We have had no experience with it, but I see 

 it occasionally in tomato-houses. It is apt to appear in 

 late winter or early spring, often not until the winter 

 in fig. 2— the experiment was easily tried. crop is nearly harvested. In such cases, the burning of 



