218 DISEASES OF TROPICAL PLANTS CH . 



to Phytophthora infestans, De Bary, and has been dis- 

 cussed in connection with the diseases of potatoes. 

 Although it has been frequently reported as a disease of 

 the tomatoes, it was not considered destructive until it 

 proved to be a very serious pest in Southern California. 

 It is not serious, except in very wet, rather cool weather ; 

 and in case it should be introduced there is every 

 reason to expect it to prove serious in the more elevated 

 parts of the tropics. It attacks the green and ripe fruits 



FIG. 74. Tomato leaves affected with blight, Septoria lycopersici. 



and the stems, causing spots which ruin the fruits for 

 markets, and under suitable weather conditions destroy- 

 ing the entire crop. It can be controlled by spraying 

 with Bordeaux immediately after each rain (page 207). 



Leaf Spot or Leaf Blight. This disease (Fig. 74) is 

 sometimes confused with the early blight, but is quite 

 different in both its general appearance and the 

 character of the fungus which causes it. The spots are 

 much smaller than in the early blight, and the lower 

 leaves are the first to be attacked. As the disease 

 progresses the leaves curl, die, and fall. The vitality 

 of the plant is reduced, and the crop is injured pro- 



