310 



[October* 1910, 



PLANT SANITATION. 



A CUBAN BANANA DISEASE. 



By Dr. Erwin F. Smith, 

 Department of Agriculture. 



(From Science, Vol. XXXI., No. 802, 

 Friday, May 13, 1910.) 



My attention was first called to this 

 disease in December, 1908, by Mr. Home, 

 of the Cuban Experiment Station, who 

 requested me to study the cause of the 

 disease. Up to this time 1 have been 

 unable to visit western Cuba where it 

 prevails, especially in bananas used as 

 shade for tobacco, but I have received 

 several lots of diseased material, and 

 now have affected plants growing in one 

 of the Washington hothouses, 



The signs of the disease so far as I 

 have been able to obtain them from 

 Cubans, and as the result of my own 

 examinations, correspond quite closely 

 to those described by Dr. McKenney, 

 and also to the banana disease des- 

 cribed by Mr. Earle from Jamaica in 

 1903. A similar, if not identical, disease 

 prevails in Trinidad, according to state- 

 ments made to me by Mr. James Birch 

 Rorer, from whom I have also received 

 alcoholic material. A similar disease 

 occurs in Dutch Guiana, according to 

 statements recently received by me from 

 Dr. Van Hall, Director of the Experi- 

 ment Station in Suriname, I am inclined 

 to think that the Central American 

 disease is also the same as this disease, 

 although we are not yet certain, Dr. 

 McKenney and myself having joined 

 forces to settle, if possible, the problems 

 relating to banana disease in these 

 regions. Possibly they are two banana 

 diseases now confused— one due to bac- 

 teria, the other to fungi. 



A microscopic examination of the 

 Cuban material showed bacteria to be 

 present in some of the vessels, but not 

 in quantity sufficient to lead me to 

 suppose them to be the cause of the 

 disease. In passing, I might say that 

 Earle sent me cultures of the bacteria 

 isolated by him from the diseased Jam- 

 aican bananas and that in the summer 

 of 1904 I inoculated these copiously into 

 the leaf-blades and petioles of bananas 

 in Washington, but without production 

 of any disease. In the Cuban plants no 

 fungi were observed at first, but further 

 studies revealed a small amount of 

 mycelium running in the vessel walls or 

 their vicinity, but in no case plugging 

 the lumen of the vessels. No spores 

 were observed at first, but after a while 

 I thought I made out, although rather 



indistinctly, one or two microcouidia, 

 and jumped to the conclusion that the 

 fungus was a Fusarium. Poured-plates 

 were then mads from the interior of 

 affected leaf-stalks which were sound 

 on the surface and a Fusarium was 

 obtained on the plates in practically 

 pure culture, the colonies having evi- 

 dently been derived from microcouidia 

 present in the bundles. Transfers were 

 made from these colonies and after a 

 half-year or more rapidly growing, large 

 banana trees were inoculated from sub- 

 cultures. The inoculations were made 

 by means of punctures into the midrib, 

 leaf-stalk and pseudo-trunk. At this 

 time the bananas were about twenty 

 feet high, perfectly healthy and with 

 trunks a foot in diameter. As a result 

 of these inoculations the writer obtained 

 infection of the vascular bundles of the 

 petiole of several leaves to a distance of 

 from five to eight feet and more from 

 the point of inoculation. The bundles 

 became brown-purple in the typical 

 manner and the fusarium with micro- 

 couidia was demonstrated in the interior 

 of these bundles by microscopic examin- 

 ation, especially after treatment with 

 10 per cent, potash (drawing exhibited) 

 and was isolated from the same at this 

 distance from the point of inoculation 

 by means of Petri-dish poured-plates, 

 the exterior of these petioles being at 

 the time perfectly sound. It has thus 

 been demonstrated beyond dispute that 

 the affected Cuban plants contain a 

 Fusarium which is able to run long dis- 

 tances inside of the vascular bundles 

 and cause a purple, purple-brown or 

 blackish stain of the same. What has 

 not yet been demonstrated is that such 

 inoculations will so disease the rootstoek 

 that other uninoculated leaves will sub- 

 sequently show the typical signs of the 

 disease. I was obliged to break off this 

 experiment after about two months, 

 owing to the necessity of moving the 

 hothouse and building another one 

 before experiments could be continued. 

 The rootstoek from which the inoculated 

 infected leaves were cut away have, 

 and additional inoculations have been 

 made, the result of which ought to be 

 positive one way or other in the course 

 of the coming year. 



The fungus may be designated for the 

 present as Fusarnim Cubense. It pro- 

 duces macroconidia and microconidia of 

 typical form, reddens and purples various 

 culture media, and has not so far shown 

 any ascospore form. The chief charac- 

 teristic separating it from other species 

 so far as yet known, is its location in the 



