TOMATO DISEASES. 
171 
appear. The former can readily be identified by the long dark brown 
or black sunken furrows or " stripes " which are produced on the 
stems and petioles. The fruits show light or dark brown sunken 
patches with round or irregular outline, which vary from a few spots 
near the calyx to many spots scattered promiscuously over the entire 
surface. The leaves develop yellow patches which soon turn dark 
brown and extend so that the greater part of the leaf surface 
becomes browned and much distorted. 
" Stripe " disease (fig. 45) is produced by Bacillus lathy ri Manns 
and Taubenhaus, which is also responsible for " Streak " of the Sweet 
Pea and other leguminous plants. The organism is carried in the 
soil and water and also in the leguminous weeds that surround so 
many nurseries. In the glasshouses it is readily spread from plant 
to plant by the workers engaged in pruning and tying, and it is highly 
probable that certain sucking insects are instrumental in this way also. 
Experiments conducted at Cheshunt have shown that there are 
considerable differences in the relative susceptibility of different 
varieties of tomatos to this disease. 
The relation between manurial treatment and the incidence of 
the disease has also been studied, and it has been shown that in- 
creasing amounts of nitrogen without potash produced an increasing 
susceptibility to the disease, while increasing amounts of potash 
without nitrogen gave a corresponding increase in resistance to it. 
Where potash and nitrogen were used together there were indica- 
tions that the potash counteracted the effect of the nitrogen. 
These results are fully confirmed by observations on commercial 
nurseries, where it has been found that plants growing rapidly 
and making large amounts of soft sappy growth are readily attacked 
by "Stripe," while slow-growing harder plants are free from disease. 
Watering with sulphate of potash solution or dressing with the 
solid compound has almost invariably caused " striped " tomato 
plants to grow away clean. 
In view of the transmission of the disease from one plant to 
another by means of the pruning knife, it is necessary to sterilize 
this instrument after pruning a diseased plant and before passing to 
a healthy one. This may conveniently be effected by wiping the 
blade of the knife with a rag soaked in 2 per cent. Lysol or similar 
disinfectant. 
" Sleepy Disease " of the tomato is found throughout the whole 
of the British Isles, where tomatos are grown, and while a large 
number of different fungi are responsible for one form or another of 
this disease, the most important pathogen in this country is a fungus, 
Verticillium albo-atrum Reinke and Berthold, but under exceptionally 
high-temperature conditions another fungus, Fusarium lycopersici Sacc. , 
may be the cause. Verticillium wilt (fig. 43, 44) first appears about 
the middle of April and increases in intensity up to the middle of 
May, when it reaches its maximum. In normal summer temperatures 
the attacks die down towards the second half of June, July, and 
