132 DISEASES OF TROPICAL PLANTS CH . 



at the tip, wilt, and eventually dry up. Examination 

 of the roots shows that they are wound or twisted into 

 a more or less compact mass. The cause of this disease 

 is unknown, but probably due in most cases to poor 

 preparation of the soil. 



Blight. - - This disease has been reported from 

 Australia, and when better understood may prove to 

 be the same as the disease previously described under 

 the name of wilt. The diseased plants are described 

 as being stunted, turning yellowish, and finally drying 

 up, dying, and rotting. The disease is due to a fungus 

 which attacks the roots, causing the tips to be pale 

 brown instead of white. 



Sun Scald. This is due to the plant bending so that 

 one side of the fruit is unduly exposed to the sun, and 

 also to the moisture which adheres unevenly to the 

 surface. The scald is followed by a rotting of the 

 fruit. 



Black Heart or Core Rot. This is a disease in which 

 the fruits ripen unevenly. Black patches occur in the 

 pulp, and it is finally entirely destroyed. The disease 

 is due to a fungus, probably Penicillium sp. ; but it is 

 thought that the lack of food or improper fertilizer 

 may prove an aggravating factor. It occurs in the 

 West Indies and other tropical countries. 



Heart Rot. This disease has been reported from 

 Cape of Good Hope. It occurs as a blackening of the 

 heart or central axis, frequently through its entire 

 length. It is a physiological disease which is said to 

 be due to excessive moisture. A similar trouble has 

 been reported from the United States. 



Fruit Rot. A fruit rot, due to an undetermined 

 species of Diplodia, has been reported from the West 

 Indies. The organism enters through the cut end of 

 the fruit stalks, and penetrates the surrounding pulp 

 tissue. The perithecia appear under the rind as small 

 black spots. Fruit rots have been reported as due to 

 the following organisms : Thielaviopsis ethacetica, 

 Went., Trichosphaeria sacchari, Diplodia sp., Peni- 



