Verticillium Wilt is suppose to affect snapdragons. Do the leaves discolor at all?
You say the problem seems to be in the roots. What did you notice about the roots? Is something eating them or breaking them? Is the soil around the roots soaking in water? What potting mix did you use to grow them in?

Here is a link that might be useful: Verticillim Wilt

Loretta, Thanks for the info. I have done dome investigating and I am leaning toward root knot nematodes though I will delve into verticillum theory.

I started seeds in soiless peat and vermiculite. They are planted in good well draining soil with a good measure of municpal compost. Mike Mcgath said this week on his show that compost from township facilities is very high quality. I have had this bed for some time now and the soil tests I did last year were good.

When I pulled the plants out the roots were stunted. The leaves on the plants didn't seem to discolor they just wilted. I have another plant that seems to be going. I will take a closer look.

I don't think in is an animal. I have rabbits and I think they can pull on plants when they eat them that can hurt the roots and kill them.

Do you have galls on the roots to indicate nemotodes? Is anything else wilting. A picture might help. If you do get a pic, you might post this on the pests and diseases forum.

You don't think it could be a form of root rot instead? What color are the roots? Are they dark especially on the growing tips?

The reason I asked about the soil is, in the past, I've had plants wilt in the ground because the potting soil didn't soak up any water once in the ground. Those were mixes with large chunks of bark or coconut coir based. I've had to remove as much soil from the roots as possible to fix it.

As far as animal, I was thinking more along the lines of underground larvae and grubs.

For what it's worth, I've had snapdragon seedlings wilt on me but I always attributed it to a damp-off disease.

Finally, you can still contract a pathogen from the county compost so don't rule that out as a source.

I have some mature snapdragons wilting. I pulled some of them up and noticed a white fungus at the base of plant at the mulch level. Is this Verticillium Wilt? If so how do I treat? Can I also treat snapdragons not yet showing signs of this. Eveyone of the effected planys were very vigorous in growth then suddenly wilted then die.
Thank you for any help.

The white fungus at the mulch level sounds more like fungus on the mulch. Pull the mulch away from the base of the plant to soil level.