WRT eelworm, it may be useful to grow French marigolds as companion plants, a substance exuded from their roots has nematodicidal properties.
I don't know whether it's simply coincidence, but I've got into the habit of edging most of my beds with them, since reading years ago of their benefits as a beneficial insect attractor, and have (touch wood!) never suffered from nematode related maladies, even when those around me have been pulling their hair out because of it.
As an accidental benefit, I've noticed that slugs and snails adore them, so they are also worth growing next to plants attractive to molluscs, as a sacrificial crop.
I'll take a few pics in the Summer to show you just how many marigolds I grow, they usually outnumber the veg plants! The blaze of yellow and orange flowers looks fantastic in the fading light of evening, and if deadheaded regularly they last right up to the first frosts.