Partly OT . . . .
Why not try growing watermelons on a sturdy trellis? That would keep the vines and developing fruit off the ground and mostly isolate the vines from soil-borne pathogens. The vines have tendrils for climbing after all, so why not give them the chance to climb?
I once saw watermelons growing hanging from an orange tree in a garden in rural Guatemala. It was kinda startling to see three or four big melons hanging from that orange tree. But in a small scale garden the fruit could be protected from falling to the ground by a cradle/net 'til ready to harvest.
And anyway, having seen that arrangement in Guatemala gave me the sense that that is part of the melon's natural strategy for distributing its seeds... Once the fruit is ripe and falls to the ground it breaks open and the interior invites being eaten along with the seeds which are then later distributed in the droppings of the creatures that ate the fallen fruit.
This could be tried with any tendrilled melon. (Or maybe someone on here is growing melons this way already.)
Paul M.
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