350 DISEASES OF CROP-PLANTS 



of opportunities for prolonged study on the spot, Howard's 

 observations have been confirmed but not materially supple- 

 mented by the successive mycologists of the Imperial Department 

 of Agriculture. 



Description of the Disease. 



The spots are very erratic in their occurrence and may be 

 found in few or many of the fruits in a given consignment ; 

 large and well-grown specimens appear to have no advantage in 

 this respect. The discoloration may be narrow and linear, 

 extending inwards for half an inch or more from the base of an 

 " eye," perhaps with one or more small bulbous expansions which 

 become cavities, or it may be in the form of a conspicuous spot, 

 of varying length and width but usually rather sharply defined. 

 It does not appear that any notable extension of the lesion occurs 

 during storage of the fruit, nor, apart from the spots themselves 

 and the disfigurement they cause, that the edibility of the fruit 

 is affected. 



A species of PeniciUium is uniformly found to occupy the 

 spots, fruiting in small cracks and in the cavities of the ovary. 

 The beginning of the spots, and the entry of the fungus into the 

 tissues, is associated, commonly at least, with perforations in 

 the tough wall of the old floral chamber (the eye), near the 

 insertion of the style. Species of PeniciUium are generally present 

 on the withered floral organs, and it is regarded as probable that 

 the fungus depends for access to the pulp on punctures made by 

 insects or mites inhabiting the enclosed floral chamber. Mealy- 

 bugs and mites are usually to be found in this situation. To 

 establish this theory of the disease it will probably be necessary 

 to study the general biology of the flower and fruit up to the time 

 the affection begins to develop, and until this has been done no 

 remedial measures can be suggested. 



Economic Aspect. 



The existence of this trouble has a serious reaction on attempts 

 to establish a pineapple industry. It is impossible to know when 

 selling, shipping, or buying pineapples whether they will or will 

 not show a disfigurement which greatly reduces their value for 

 table purposes. 



Thielaviopsis Soft-Rot. 

 Pineapples which are bruised in gathering or in transit or 

 which sustain an injury while stiU on the plant are liable to be 

 attacked by the fungus Thielaviopsis paradoxa, which spreads 

 rapidly through the fruit and sets up a soft and watery rot. When 

 the infested tissues are exposed they are quickly blackened by the 

 abundant development of spores which then takes place. This 

 is the commonest type of decay in the harvested fruit, whether 



