MARKET DISEASES OF VEGETABLES. 67 



In the early as well as the later stages, nail-head spot is 

 marked by small, dry, slightly though abruptly sunken scab- 

 like spots which are brown to black in color. 



These spots or lesions generally are mere blemishes, and 

 cause little damage. The lesions may be circular or ellipti- 

 cal and at times may coalesce to form a large, irregularly 

 shaped area. At times the spots on ripening fruits are sur- 

 rounded by a green zone due to delayed ripening of the 

 bordering tissue. The tissue underlying the spot is not 

 affected, and the diseased tissue can easily be removed from 

 the sound tissue underneath. As the lesion ages, it often 

 cracks and opens the way for the entrance of secondary rots 

 such as Phoma. 



The small size and the slightly sunken, flat and scab-like 

 nature of the lesions of nail-head differentiate these from 

 the lesions of other tomato fruit diseases, most of which, in 

 contrast, are large or water-soaked, often deeply sunken 

 and involve more rotting of the tissue. 



Nail-head spot is a warm-weather disease, and is preva- 

 lent on fruit from the Gulf States. It is a serious field dis- 

 ease, attacking leaves, stems and fruits, and is known by the 

 growers as early blight. The fruit is infected before it 

 leaves the field, and the spots are visible when the fruit is 

 packed. The spots may enlarge slowly in transit and 

 storage. 



Spraying will control the disease in the field. In packing 

 it is advisable to sort out spotted fruit because its presence 

 lowers the market value of a shipment and affected fruits 

 are predisposed to rots. 



Ref. (56); (60). 



TOMATO: PHOMA ROT. 



Cause: A fungus (Phoma destructiva). 



In its early stages, Phoma rot is marked on the green fruit 

 by minute, slightly sunken circular spots with a brown or 

 black border and a lighter center. Later the center of the 

 spot becomes covered with black pimple-like bodies. These 

 are known as pycnidia (singular pycnidum). In the early 

 stages, spots on ripe fruit are water-soaked and concave. 

 Later, as they enlarge, the centers become brown to charry 

 black, leathery and firm, and covered with pycnidia. The 

 borders are slightly sunken and water-soaked. The lesions 

 increase indefinitely and quite rapidly in size but remain 

 more or less circular and concave. 



The lesions generally occur at the stem end of the tomato, 

 and the disease is often known as stem-end rot. The spots, 

 however, are not confined to this part of the fruit, as the 

 fungus may attack the fruit wherever it is bruised or in- 

 jured. The fungus may also enter through nailhead spots. 

 Until the lesion becomes very large, the underlying brown 

 or black tissue is quite firm. 



