Hi Organicbynature, Welcome to the Gardeners Forum.
Reason mainly is that my soil is plagued by eel worms or somesuch.
While waiting for organicby nature's reply,
You can try companion planting with French Marigold [Tagetes patula]. The marigold roots secrete chemical that kills/reduces eelworms population. Since you are planting potatoes
in tubs, just make sure there drainage holes at the bottom of the tubs. If possible, use fast draining acidic soil with a pH range of 4.8 to 5.4.