THE CUBA REVIE W 



Mosaic Disease 



What scientists declare to be the great- 

 est discovery of the century in the field 

 of plant diseases was announced at the 

 annual meeting of the American Associa- 

 tion for the Advancement of Science, 

 which was held at Cambridge, Mass., early 

 in the year. 



The declaration was made after reports 

 prepared by Prof. Ray Nelson of the 

 Michigan Agricultural College, Dr. L. 0. 

 Kunkel of the Hawaiian Experiment Sta- 

 tion, and H. H. McKinney of the Uni- 

 versity of Wisconsin had been read before 

 the association. In their reports these sci- 

 entists announced that, during the past 

 year, they had discovered the organisms 

 which cause the "mosaic disease" iri vari- 

 ous plants and they substantiated their 

 findings by displaying photographs of these 

 organisms actually at work. 



Important to Sugar Industry 

 While this discovery is of great im- 

 port to all plant pathologists, it is of spe- 

 cial interest to those who are concerned 

 with the study of the diseases of the sugar 

 beet and sugar cane, for the reason that 

 the mosaic disease is increasing every year 

 and it is estimated that it results in the 

 loss of tens of thousands of dollars' worth 

 of sugar plants annually. 



For many years plant pathologists have 

 been searching for the cause of the mosaic 

 disease, on the theory that if they could 

 find the organisms they could devise means 

 of controlling the disease. With the find- 

 ing and photographing of these organisms 

 accomplished, the mystery of the disease 

 has been revealed. 



The organism is described as having a 

 long spindle-shaped body with whip-like 

 hairs (cilia) at each end. They are con- 

 sidered as belonging to the most primitive 

 forms of animal life, the protozoa. They 

 are less than one hundred-thousandth of 

 an inch thick and from ten to twenty times 

 as long. They attack the cell in its most 

 vital spot, the nucleus. Some of them 

 have been found actually coiled about the 

 cell nucleus. 



Specimens Found in Potatoes 

 While it is true that scientists have be- 

 lieved for some time that the mosaic or- 



ganisms belonged to the animal kingdom, 

 no one was able, until recently, to prove 

 this a fact, nor had anyone been success- 

 ful in observing the organisms actually en- 

 gaged in their depredations. Prof. Nel- 

 son reported that he had found the or- 

 ganisms by cutting thin sections of the 

 inner part of infected potato stems and 

 examining them under a high powered 

 microscope. 



It has also been found that there are 

 various kinds of these organisms, each 

 preying on a particular sort of plant. The 

 organisms discovered by Prof. Nelson are 

 those that infest beans, sugar beets, clover, 

 tomatoes, and potatoes. These creatures 

 are similar to the trypanosome, the cause 

 of the sleeping sickness which kills man 

 and beast in Africa. 



Dr. Kunkel and H. H. ]McKinney an- 

 nounced the discovery of the parasites that 

 cause the mosaic disease in corn and wheat 

 plants. It was found that these organ- 

 isms belong to the class known as ameba 

 and are similar to the organisms causing 

 malaria and yellow fever in man, which 

 are transmitted from man to man by 

 the mosquito. 



While it is too early to announce the 

 measures to be taken in the control of 

 these organisms, it is the belief of many 

 prominent botanical pathologists that their 

 discovery may be the beginning of a new 

 era in the treatment and cure of many 

 plant diseases. 



A factor to which too little attention 

 has heretofore been paid in surveying crop 

 conditions and prospects in Cuba is the 

 mosaic disease of sugar cane, which by 

 reason of its widespread existence and in- 

 creasing dispersion seems to have reached 

 a point where it deserves consideration 

 along with the rainfall and weather condi- 

 tions in general. Just how much territory 

 in Cuba has been invaded by this disease, 

 and to what extent, has never been deter- 

 mined by an accurate survey, although it 

 has been known to exist in several parts 

 of the island for a number of years. The 

 reasons for this lack of attention to what, 

 in other countries, has been recognized as 

 one of the most serious menaces to suc- 

 cessful cane agriculture have been vari- 



