Native cat tails such as typha latifolia are a common sight on many
ponds quite simply because someone was silly enough to chuck a few
'free plants' in and later discovered it was a big mistake. The only
reason you see them on so many ponds is because they are so difficult
to get rid off... they will fill any pond in, eventually, that's all
they do.
You could try dredging them with an excavator, however there will
still be some roots left that will sneak back in the future.
You could try hand weeding them one by one dragging each rhisome out,
you could try a herbicide and kill the whole pond, or try stroking
'round up' on each stem
There's only one efficient solution for cat tails on a pond, never let
them start on a pond in the first place, unless its a carefully chosen
small variety like graceful cat tail, typha laxmanii

http://www.members.aol.com/abdavisnc/swglist.html
(andys aquatic plant list for interesting swaps

"Tony Brennan" wrote in message ...
Grateful for any help on the problem of control cattails. I have a heap of
them round the edge of my pond (natural) but I'm worried about them taking
over. They seem to be spreading toward the middle.
Tony