144 Diseases of Economic Plants 



$100,000 annually. Resistant stock should be used; diseased 

 parts should be excised, and antiseptics applied. 



Die-back is characterized by gum pockets, stained terminal 

 branches, ammoniated fruits, bark excrescences, and multiple 

 buds. The disease is important but the cause is unknown. 



Melanose {Phomopsis dtri Faw.) is a disease of foliage, 

 young twigs, and fruits, in which small, dark, elongated spots 

 are produced. Weak Bordeaux mixture should be used. 



Blight, with wilting of foliage and death of twigs and 

 branches, is of unknown cause. In many ways it resembles 

 peach yellows. 



Minor diseases 



Citrus-knot {Sphceropsis tumefaciens Hed.), troublesome 

 in Jamaica, and once found in Florida; various leaf-spots; 

 Sooty-mold ^™' ^^^ consisting of a black, superficial fungus 

 {Capnodium) ; Algal leaf-spot produced by Cephaleuros 

 virescens; Crustose lichens; Dodder and Mistletoe, occa- 

 sionally attacking citrus fruit trees; Sour-rot of lemons 

 (Oidium citri-cmrantii) , also called slimy-rot and watery- 

 rot occurring during storage; Crown-rot (Sderotimn rolfsii); 

 Wood-rot due to several large fungi ; Die-back and stem-end- 

 rot (Diplodia), and Pink-disease {Corticium) are of minor 

 importance. 



COCOANUT 



Bud-rot ^^"^ {Bacillus coli (Esch.) Mig.) is the most seri- 

 ous disease of this palm. It is of wide and growing dis- 

 tribution in the American and Eastern tropics. An annual 

 loss of £4500 is reported from one plantation in Jamaica. 

 A soft rot occurs in the terminal bud, the growing point, re- 

 sulting in the death of the tree. Badly diseased trees and all 

 infected refuse should be burned. 



COFFEE 



RuSt (Hennleia vastatrix B. & B.). — This most destruc- 

 tive coffee disease, believed to have spread to coffee from 



