Posted: 18/06/2013 at 18:41
Hi Suzanne, depends what 'root worm' is. If it's cabbage root fly which attacks all brassicas - see here:
then planting any other brassicas in their place will very likely be a problem. You could treat the area with Nemasys Grow Your Own (as mentioned in the RHS link above) which is a mixture of nematodes which prey on cabbage root fly (and many other pests) and will help to clear up the problem. Crop rotation is a must once you have had a root fly infestation, so don't grow any brassicas in that piece of ground next year.