This ecocatastrophe versus beneficial 

 stimulus argument is not completely re- 

 solved. Probably, Sphaeroma root destruc- 

 tion, in areas of low isopod density, can 

 be a beneficial process to both the in- 

 dividual tree and to the entire mangrove 

 stand. Whether changes in freshwater 

 runoff have accelerated this process to 

 the point where unnatural and widespread 

 damage is occurring is not clear. The 

 data and research perspective to answer 

 this question do not exist. As a result, 

 we are reduced to providing hypotheses 

 which cannot be tested with available 

 knowledge. 



2.8 MANGROVE DISEASES 



Published research on mangrove 

 diseases is rare. The short paper by 

 Olexa and Freeman (1975) is the principal 

 reference for diseases of Florida man- 

 groves. They reported that black man- 

 groves are affected by the pathogenic 



fungi , Phyl losti eta hi bi scina and Nigro- 

 spora sphaerica. These authors found that 

 P. hi bi sci na caused necrotic lesions and 

 death of black mangrove leaves. They felt 

 that under conditions of high relative 

 humidity coupled with high temperatures, 

 this fungus could pose a serious threat to 

 individual trees, particularly if the tree 

 had been weakened by some other natural 

 agent, such as lightning or wind damage. 

 Nigrospora sphaerica was considered to be 

 of little danger to black mangroves. 

 Another fungus, Cyl i nrocarpon didymum , 

 appears to form galls on the prop roots 

 and stems of red mangroves. Olexa and 

 Freeman (1975) noted mortality of red 

 mangroves in areas of high gall infesta- 

 tions, although a direct causation link 

 was not proven. 



Further research on mangrove diseases 

 is badly needed. Viral disease must be 

 investigated. The role of pathogens in 

 litter production and as indicators of 

 mangrove stress may be very important. 



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