I use "Benlate" ,but Im not sure if its still available ,I had quite a few packets of it in my shed ,but am down to the last one .
Another that you should be able to get is "Fongarid "
These are sold here in OZ.

Lis, I use Hortico Rose dust fungicide and insecticide. It is amazing stuff for me. I put it on any rotting cacti and succulant and providing it is not too far gone it stops rotting. I use it also on seedlings to avoid damping off , i dust seedlings then water it in.
Tammy

Thanks for your advice Kev and Tammy.
Tammy I'm glad you've had real success with the Rose dust, I'll definately keep that in mind now! I saw Fongarid in the stores but ended up buying Yates Garden Spray insecticide fungicide. I did some research on the net and found a list of the best fungicides for what I thought my cacti have, and this one had more of a combination of these. I did nearly get the Fongarid but the insecticide part of this preparation sounded pretty good to me too. I plan on trying it in a weakened solution first of all on my sickies first, and then if they don't shrivel up and die I'll use it on all of them regularly, as a preventative and a cure. I am also planning on going through all my plants and giving them a good once over. I've been thinking of repotting them with my normal cactus mix down the bottom but with perhaps only pure coarse sand for the top 1/2 to 1/3 of the pot. I hope that this will keep water away from the base of the plant, and also deny any potential fungal, bacterial or insect invaders an organic foothold. Do you think this will work?
Will let you all know how this Yates stuff works anyhow.
Cheers, Lis :D

Littlelisie,
I would use gravel instead of the sand around the neck of the cactus (between the top of the roots and the base of the cactus) this will allow air to get to the neck ,I found if this area stays wet ,you have a higher risk of fungial rot. Sand would tend to hold the water.

Thanks Kev, I thought sand would be quite quick draining but the coarser the better makes sense. I'll have to go round some landscaping supplies places and get me a load. Do you bother about top dressing for aesthetic purposes once you have gravel on top of your plants? I've been using stuff like crushed bricks and small stones on top of the soil, but it's just a small layer to cover the earth and won't substitute for the depth of gravel I want to use.
I gave the sick plants a dose of that stuff today, over the plant surfaces and onto the soil to be soaked in, I used 2/3 strength and will probably give them another dose in a week's time and see how they go.
Cheers, Lis :D

Yes I top dress I usually have the gravel about an inch deep to keep the neck of the plant away from the soil .
The plant will send roots into the gravel if it wants to.
The gravel I use fits through a 3/16-1/4 inch wire mesh .
It's just gravel I get from creek beds and road side culverts in my local area ,mainly ironstone or limestone.
You might try some of the bigger garden supply places where they have large amounts of different crushed stone etc, when in Adelaide I went to "Jefferies garden supplies" and took some large buckets ,I bought diffent size gravels and it worked out very cheap. They hade a nice pile of finely crushed blue metal as well.

Thanks TammySara,I have found the Hortico Rose dust fungicide and insecticide terrific, I use it all the time , I wouldn't be without it now.

If you can find a local Chemical Supplier. Get some plain Sulphur which is probably the main ingrediant in your Rose Dust and use it. If i have a plant that has rotted off i cut of the rotted part dust with sulphur, leave till it has calloused & then sit it on a pot till it reroots. I use red scoria as a potting mix for 99% of my plants and have very little trouble with rotting as it drains through very quickly. Roger takes care of the Mealy bug when they show them selves.

MealyBug, It's impossible to find just plain sulphur up in the far North ,I have looked, I did buy some at great cost, but it was the wrong one,as for red scoria, no hope in finding that here,unless someone can help......