84 DISEASES OF TROPICAL PLANTS 



CH. 



Borneo, Tonquin, Java, Argentina, Queensland, and 

 the Hawaiian islands. 



The nature of the disease is such that the only 

 remedies that can be recommended at this time are 

 such cultivation as will insure healthy 

 plants, the burning of refuse and the 

 sterilization of cuttings by dipping in 

 weak Bordeaux mixture. 



The Pineapple Disease (Thielamopsis 

 ethacetica, Went) (Fig. 39). This is a 

 stem disease which originates in the 

 cuttings for planting and frequently 

 prevents them from growing. The 

 plants which do succeed in growing 

 from these diseased cuttings are usually 

 diseased. The diseased plants are not 

 conspicuous during the early periods 

 of this disease, in fact, they frequently 

 cannot be separated by the external 

 appearance from the healthy plants. 

 However, the interior becomes filled 

 with the fungus, which produces an 

 abundance of sooty black spores. No 

 perfect stage of this fungus is known. 



This fungus is primarily sapro- 

 phytic, but readily becomes parasitic 

 when it gains entrance through a 

 wound. It thus readily attacks the 

 cuttings which are made for plantings, 

 causing the cut surface to become 

 blackish in colour. When these dis- 

 FIG. 39. -sugar- cane eased cuttings are split open they show 

 affected with "pine- red or cinnamon colour, and if the 

 b? P c!' w! S Edg;r ( t P on?r disease is well advanced they show large 

 black blotches with red margins. In this 

 condition they give a characteristic odour of pineapples, 

 therefore the name. Many of these diseased cuttings die 

 without germination, while many of those which do ger- 

 minate die later, or produce weak, unprofitable plants. 



