982 MICROBIAL DISEASES OF PLANTS 



a short distance, rotting out the fundamental tissues and leaving only 

 the fibers which are too hard to be disintegrated. 



It has been estimated that in some cocoanut groves from 75 to 90 

 per cent of the trees have been destroyed by the rot. 



CAUSAL ORGANISM. B. coli (Escherich) Migula. 



METHOD OF INFECTION. It is believed that the causal organism 

 enters the host through insect bites or other mechanical injuries to the 

 soft tissue. Insects, birds or some form of animal life are held respon- 

 sible for spreading the trouble. 



CONTROL. The removal of the diseased parts of a tree as well as 

 spraying have proved of no benefit in controlling the disease. "The 

 absolute destruction of diseased trees, a careful watch for the newly 

 infected cases, and their immediate removal has done much to prevent 

 greater loss in the various regions." 



BROWN ROT, A LEAF-DISEASE OF TROPICAL ORCHIDS 



Bacillus cypripedii S. Hori 



HISTORY AND DISTRIBUTION. The brown rot of orchids was first 

 observed by Hori* in 1906 on orchids growing in the greenhouses in 

 Tokyo, Japan. Since then the disease has been noted on orchids from 

 Formosa grown in their natural habitat out of doors. In 1898 v. Peg- 

 lionf described a similar trouble in Italy which may be identical with 

 the above. 



SYMPTOMS. The rot is characterized by dirty cinnamon or light 

 umber colored, depressed spots on the leaf -blade; these become darker 

 with age and may increase in size so rapidly that the entire green leaf 

 is discolored (yellowish) in a few days and dies. The rotting also 

 spreads downward into the stem, and if the diseased leaves are not 

 removed early, the entire stalk will be destroyed. 



CAUSAL ORGANISM. Bacillus cypripedii is a medium-sized rod with rounded 

 ends; single or in short chains; measures 1.5 to 2ju X 0.5 to o.y/j; stains readily with 

 aniline dyes; Gram-positive; motile by 4 peritrichate flagella; non-spore forming; 

 smooth, light grayish white colony, with pearl luster on agar; dirty cream colony 



*Hori, S. f "A Bacterial Leaf-disease of Tropical Orchids," Cent. f. Bakt., Abt. II, Bd. 31, 

 p. 85, 1911. 



t v. Peglion, "Bacteriosi delle folie di Oncidium spec," Cent. f. Bakt., Abt. II, Bd. 5, 

 P. 33, 1899. 



