250 DISEASES OF CROP-PLANTS 



actually reached the fruiting stage. The effect on the plant is 

 that of shortage of water, and the view of an infested field conveys 

 the impression that all the outer leaves have been scorched. 

 The leaves wither in the order of their age, their tissue drying 

 up from the margin towards the midrib. Bearing plants fail 

 properly to mature their fruit, which commonly dries hard and 

 black while only partly grown. 



Examination of the base of the plant shows many roots partly 

 or entirely blackened, and extensive black patches, or a general 

 blackening of the external tissues, present on the rootstock. 

 Slices of the diseased rootstock show peripheral blackening 

 penetrating to a depth of about an inch in places, and blackened 

 areas isolated in section but connecting with the exterior at a 

 higher or lower point. The thick roots have short swoUen cracks, 

 connecting with extensive discoloured patches spreading upwards 

 and downwards in the tissue of the cortex, reaching in many 

 cases to the central vascular cylinder but not penetrating it. 

 The discoloured tissue is in various stages of disorganisation, but 

 in much of it the cell-walls are not visibly decayed. The nema- 

 todes have been found to be regularly present in all the material 

 examined ; their eggs occur in the least altered and deepest 

 seated of the discoloured tissues, and the worms themselves 

 may be seen in the cells of undecayed tissue close to the central 

 cylinder of the roots. 



Resistance and Control. 



The effects of the disease show up most plainly in dry weather. 

 There is evidence of a considerable measure of recovery during 

 the more favourable conditions of the wet season, presumably 

 because more rapid root development has gained on the progress 

 of the infestation. This points to the usefulness of good cul- 

 tivation in the control of the disease. The use of suckers from 

 affected clumps as planting material should be carefully avoided, 

 and where land is badly infested the bluggoe should be replaced 

 by some other plant. The Chinese banana and the " silk fig " 

 when seen growing amongst infested bluggoes have been much 

 less severely affected. The former at least seemed to be resistant 

 to a degree which might permit of its successful cultivation in 

 infested soil. 



The worms are too small to be seen with the naked eye, 

 their length being only a little more than half a millimetre. 



Diseases described from Jamaica. 



Several diseases have been described from Jamaica by S. F. 

 Ashby which have not been met with so far in the Lesser Antilles. 

 This may be due to the fact that bananas are grown only in a 

 scattered way, so that there is less opportunity for disease to 

 become noticeable. It seems desirable to include brief accounts 



