148 Diseases of Economic Plants 



this disease is prevalent in certain regions of California, 

 occasionally causing the leaves to turn yellow and injur- 

 ing the appearance of the fruit. Usually it does but 

 little harm. Spots 2-4 mm. in diameter occur upon the 

 leaves. They are composed of concentric rings of different 

 colors, giving them somewhat the appearance of the spots on 

 peacock tail feathers. The spots on the fruit are smaller and 

 more decidedly brown in color. 



The use of Bordeaux mixture checks the trouble. 



Sooty-mold occurs nuich as on citrus fruits and Root-rot 

 (Ar7mllaria mellea) as on other orchard trees, p. 51. 



PINEAPPLE 



Black-heart {Thiehiriopsisparadoxa (d. Seyn.) v. Hohn). ^ 

 This rot of fruit may be found in abundance in any market 

 and causes the loss of many carloads of fruit. It usually 

 begins at the stem-end and progresses through the center of 

 the fruit as a soft rot, in later stages turning black, due to the 

 formation of many spores. Other fruit rots are due to 

 Diplodia, Trichosphseria, Penicillium. Other pineapple dis- 

 eases are: Rot of young plants due to soil fungi. Wilt and 

 Chlorosis. 



PLANTAINS. See banana. 



VANILLA 



Numerous diseases are recorded on this orchid. The most 

 destructive is caused by Calospora vanillce Mass., which 

 grows on stems and leaves, and eventually kills the entire 

 plant. Other parasites are Vermicularia, Colletotrichum, 

 Gloeosporium, Uredo, Uromyces and Nectria. 



