TYLENCHUS SIMILIS, THE CAUSE OF A ROOT DISEASE 

 OF SUGAR CANE AND BANANA 



By N. A. Cobb, 



Technologist in Charge, Office of Agricultural Technology, 



Bureau of Plant Industry 



OCCURRENCE OF TYLENCHUS SIMILIS IN FIJI AND HAWAII 



A serious outbreak of a disease among bananas (Musa sapientum) in 

 Fiji in 1890-91 caused the planters great uneasiness. At the request 

 of Sir John Thurston, British High Commissioner of the Pacific, the 

 Department of Agriculture of New South Wales, Australia, undertook 

 an investigation, which was conducted by the writer. Most of the banana 

 plants examined grew in the gardens adjacent to Government House 

 at Suva, Fiji, where experimental plantings were made in connection 

 with the disease. During the investigations roots of the banana and 

 the soil about the roots were examined with a view to discovering pos- 

 sible causes of the disease. It was during this particular part of the 

 investigation that a new species of nematode was discovered, to which 

 the name "Tylenchus similis" was applied. Only the male was seen. 



Nothing further was discovered concerning this species of Tylenchus until 

 1907, when, during a visit to sugar plantations on Kauai, one of the Hawa- 

 iian Islands, the same nematode was again found by the writer, this time 

 infesting the roots of sugar cane (Saccharum officinarum). Both sexes of 

 the nematode were found in abundance, and to these specimens, which 

 at the time appeared to represent a new species, the name "Tylenchus 

 biformis" was applied. T. hiformis proved to be a true parasite and was 

 found to be sufficiently injurious to the roots of sugar cane to justify a 

 careful examination. 



The nematode appeared to attack the roots at or near the tips, with 

 the result that the root soon succumbed, thus compelling the plant to 

 throw out new roots, which in turn became infested. The attacks of the 

 nematode resulted in striking lesions, easily discoverable whenever the 

 attacks were of a pronounced character. The tissues of the root lost 

 their white or colorless appearance and took on first a cinnabar-red color, 

 then a reddish purple color. The latter was succeeded by a dark pur- 

 lish red, and this in turn by a purplish black. The discolored areas 

 were sometimes several millimeters in length. In advanced cases the 

 tissue of the axial part of the root was attacked, and large numbers of the 

 nematodes were readily discovered in the colored cavities caused by 

 their activities. The seriousness of the result was increased by the fact 



Journal of Agricultural Research, Vol. IV, No. 6 



Dept. of Agriculture, Washington, D. C. Sept. 15, 1915 



, . G-55 



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