.

In my part of the world Takeall is also known as Haydie, simply because of when the effect starts to show, as the crop is "haying off', and  all these dead heads start to appear.   Despite that, it is actually a  seedling disease. 

 Your question regarding no wheat for 18 years, isn't as simple as it appears, and I have no idea what you refer to as a ''standard rotation".   The fungus is hosted and propagated by many  pasture grasses, in particular Barley Grass, and  all cereals, except oats, as far as I know, and is rather like a hardening of the arteries  for plants.  The plumbing is blocked by the fungus, so moisture/nutrient flow  is restricted, killing the head off at grain fill.  I had never thought about it before, but perhaps this is more easily seen in an environment like mine, where increasing temps and decreasing moisture supplies at ripening, is the norm. I don't know. 

Often a rain at that stage makes the problem appear worse, but I understand that isnt really worse...just easier to see.

An interesting thing is that  we used to have very, very  significant problems  with it.   In those days  this area had a low intensity of cropping, meaning any particular area of ground was not usually cropped every year. So the intervening years  mostly had  barley grass, along with some  volunteer pasture legumes, to run sheep.  As we have  increased the intensity of the cropping to  mostly every year, the problem seems to have disappeared, such that we dont hear of it, and don't think of it any more. And we grow cereals on cereals mostly, and wheat on wheat sometimes.   I think that's largely due to the removal of the barley grass.  As well, a natural suppression is supposed to eventually build up.   All i know is that (touch wood) it seems to be of no significance any more, whereas it once was a major issue.

I have no personal experience, but Flutriafol  ( Impact  or  Intake ) in the seed row ( in our  case it is with granular fert ) is supposed to give  "up  to 70% rdeduction in the damaging effects "......whatever that actually means.

http://www.abb.com.au/Portals/0/Fertiliser/Intake_Flyer.pdf     I understand  the benefit with takeall is not from the curative effect of the fungicide flowing around the plant, but from  the direct contact with the fungus in the soil.

Likely other  funcides are as good or better, ...or not.     But  these days it is a relatively cheap exercise, and can have other benefits as well.

I know some years ago there were predictive DNA soil tests being developed which were designed to give an estimation of the likely risk, but i dont know what's happened with them of late, or if they are available to you.

Just the difference in our soil pH  is likely to alter our  experiences with it.   Mine is  mid 8's