120 T BIN ID AD AND TOBAGO BULLETIN. [XIK. 3. 



The following common cane insects have been tested during the past 

 six months by sleeving them on infected canes and then transferring to- 

 healthy stools. 



The froghopper {Tomas2)is saccharina). 

 Corn leaf hopper (Peregrimis v^aidis). 

 A Cane leaf hopper (Te.ttigoriella laudato). 

 A Cane membracid [Cercsa vitnlus F. var. minor Fowl). 

 In no case was the disease transferred. 



The only other common insect in the field which seems sufficiently 

 abundant to account for the known spread is the mealy bug and 

 experiments with this ai'e proceeding. 



Possibility of Spread through Ground. 



The corn plants refex'red to above as infected with mosaic disease 

 were planted in the holes from which diseased canes had been removed, 

 and it was suggested by our inspector that they had become infected 

 either from the soil or from small pieces of diseased roots which were 

 left behind in the soil. 



To test this 50 cane cuttings and 50 corn seeds were planted in holes 

 from which diseased stools had been removed at the St. Augustine 

 Experiment Station. A like number of cane and corn were planted as a 

 control in holes in the same beds from which healthy canes had been 

 removed. 



In no case did the mosaic develop in the resulting corn or cane 

 plants. 



This suggests that there is little or no danger of infection by 

 replanting in old holes. 



THE DISTEIBUTION OF THE MOSAIC DISEASE 

 IN THE PLANT. 



It has been generally stated that all cuttings taken from a diseased 

 plant will reproduce the disease. 



This is practically true of "plants which show symptoms of the 

 disease in all stalks and have been infected for some time (i.e. those 

 grown from infected cuttings). 



Experiments made during the past year indicate however that when 

 field infection takes place, the cane becomes infected from the growing 

 point or leaves, and that it takes an appreciable time for the disease to 

 descend the stalk to the ground level. The spread from one st ilk to 

 another in a stool is still more slow, and in many cases does not occur. 

 Cane stools may be frequently found with one stalk well infected and 

 the other stalks healthy. 



In all probability in these cases there is no living underground 

 connection between the different stalks in the stool. 



The first experiment was designed to test the possibility of apparently 

 healthy stalks iit a diseased stnol transmitting the disease. Top and 

 bottom cuttings were taken, from 84 diseased stalks and 27 healthy 

 stalks, obtained from 25 recently infected stools showing both healthy 

 and diseased stalks. 



Every plant from the healthy cuttings came up healthy, although the 

 original stools from which they came had diseased stalks. 



