VASCULAR DISEASES OF BANANA. 



EARLE'S JAMAICAN DISEASE. 



In 1902, F. S. Earle saw a new banana disease in Jamaica and published a brief note on 

 it in his "Report on a trip to Jamaica. " The disease is called the banana leaf-blight, and his 

 account of it is as follows : 



On one locality at Stony Hill, north of Kingston, a serious banana disease was observed. It 

 causes the browning of the vascular bundles in the veins and midrib of the leaves. This is soon fol- 

 lowed by the blackening of the entire leaf-blade, and eventually by the decay of the leaf and petiole. 

 It does not seem able to extend from the petiole into the tissue of the stem. The terminal bud is not 

 attacked, but continues to push out fresh leaves. These soon become infected in turn, so that usually 

 not more than three or four of the younger leaves are free from the disease. Infected plants are much 

 stunted in growth and do not bear fruit. In the small field where it was first observed fully three- 

 fourths of the plants were infected. The contagion was in this case probably introduced with the 

 suckers that were used for planting, as these were said to have been taken from some neglected patches 

 in the neighborhood, and a visit to these showed that they were also infected. The disease evidently 

 spreads slowly, as it had not crossed a wide hedge row separating this infected field from one adjoin- 

 ing. It may never prove troublesome, but the advisability of immediately destroying all diseased 

 plants was strongly urged. If so destructive a disease should by any chance become widely scattered 

 the result would be truly disastrous. 



Apparently it is due to a bacterial parasite. Cultures were obtained and it is hoped to study the 

 disease further. No evidence was secured as to the means by which it is conveyed to the fresh leaves 

 or from plant to plant. So far as known it is confined to this one locality, which is at an elevation of 

 some i ,200 feet and on red land. Such locations are not considered to be adapted to bananas, yet all 

 uninfested plants were growing and fruiting satisfactorily. 



Subsequently Earle sent a culture of the whitish schizomycete which he had isolated to 

 the writer, who made numerous inoculations on banana shoots in the summer of 1903, 

 pricking in the organism from young, actively growing cultures, but obtained no signs of 

 the disease. The organism was not infectious. 



SMITH'S CUBAN DISEASE. 



In the autumn of 1908 a banana shoot, similarly affected, was sent to me from Cuba, 

 and subsequently rooted plants. Some of the vessels of the leaf -stalks were yellowish, and 

 many were brown or purple-brown. Bacteria were present here and there in some of the 

 vessels, but so sparingly that they seemed to stand in no causal relation to the disease. 

 Subsequently a fungous mycelium was detected in the vascular bundles, in and behind the 

 walls of the vessels, seldom filling the lumen. This was not very abundant in any particular 

 vessel and appeared to be sterile on first examination, but upon further study the writer 

 saw one or two indications of conidial fructification, i. e., hyphae ends constricted so as to 

 cut off partially an elliptical oblong terminal portion. Very few free spores were seen, but 

 the appearance seemed to point to the conclusion that the fungus was a Fusarium, and 

 poured plates made from the interior of diseased petioles subsequently justified this con- 

 clusion. Conidial colonies of Fusarium came up on the poured plates, and transfers from 

 these colonies to sterile cornmeal-mush fruited abundantly. The mycelium on this sub- 

 stratum was whitish at first, but soon pink, becoming a beautiful strawberry-purple on top 

 and deep wine-red below the surface of the fungous mat. Old cultures of this fungus were 

 given to Dr. Wollenweber for further study. The surface of these internally diseased 

 petioles was free from fungous spots and from other signs of disease, and was, moreover, 



168 



