In Article <mturner.513.000FBFE9@acpub.duke.edu>
mturner@acpub.duke.edu (mel turner) writes:
>In article <3lfl14$r7d@nikau.palm.cri.nz> agpcrv@palm.cri.nz writes:
>>mturner@acpub.duke.edu (mel turner) writes:
>>> agpcrv@palm.cri.nz writes:
>>>>I am making this enquiry for a friend who is farming in a dry region of 
>>>>South Africa. His dam is overgrown with Azolla to the extent that the
>>>>entire water surface has been covered. Does anyone have any experience 
>>>>with eradicating this water fern?
>>>>Any help would be much appreciated   
>     As someone else posted,  Salvinia would be using the excess (farm 
>runoff?) nutrients from the pond water, whereas Azolla would in addition be 
>able to fix atmospheric nitrogen.   Someone with say, a rowboat, a long &  
>fairly fine-mesh net, and assitants on shore should be able to skim large 
>areas of pond surface fairly quickly, and the effect would be to remove large 
>amounts of excess nutrients from the water that could then be returned to the 

Thanks for your suggestions everyone. I spoke to a scientist who said the
only way to control it effectively using chemicals was to spray with paraquat.
He said if the dam was deep enough the fish would not suffer toxic effects. I
feel the best option to avoid damaging the dam is to harvest it. I will send
the farmer your thoughts and let you know what eventually happens.