VII 



TOMATOES 219 



portionately. It is common in the tropical and tem- 

 perate regions of America. 



The disease is caused by Septoria ly coper sici, Speg., 

 a fungus which lives from season to season on the old 

 and dead leaves. Therefore, all debris from the tomato 

 field should be destroyed. Spraying with Bordeaux 

 during the early part of the season is successful in 

 combating the pest, and should be used wherever 

 practical. 



Rosette. This disease, which has already been dis- 

 cussed in connection with the potatoes, causing a 

 dwarfing of the plant, curling of the leaves, and other 

 abnormalities, has been reported from many parts of 

 the world. In some places it is known to result from 

 the attack of the root fungus, Corticium vagum, (B. & 

 C.), var. solani, Burt (Rhizoctonia), but it is by no 

 means certain that this is the only cause. It can be 

 controlled by the rotation of crops and free use of 

 lime. 



Leaf Curl. This is not due to an organism, but to 

 any one of several causes. It may be due to too much 

 moisture in the soil, or to the excessive pruning of the 

 plants. Plants affected with this disease are less pro- 

 ductive than healthy plants. 



Mosaic Disease. This is similar to the mosaic disease 

 of the tobacco. The leaves are more or less distorted, 

 and frequently reduced in size, and variegated into light 

 and dark green areas. The disease is said to be due to 

 malnutrition. (See the disease of tobacco, page 152.) 



Hollow Stem. In this disease the plants appear to 

 be normal until of considerable size, when they show a 

 tendency to fall over. An examination shows the stems 

 to be hollow. It is due to too much nitrogenous 

 fertilizers. 



Nematodes. These little pests are sometimes the 

 cause of very heavy losses. They have been discussed 

 in other relations, so that it is not necessary to give 

 them further consideration. 



White Mould or Phytoptosis. This disease (Fig. 75) is 



