those sandworms (bigger, a lot bigger, than the normal terrestrial ones) don't pay attention to what they eat... watch your harvester closely, commander!
Having lost a great number of harvesters (and units), I tried succesfully a new "agressive" policy against the worms. Once you have the stomper units(the one with the stomper,lol),or the atomics(harkonnen only), you have all the weapons in hand; find a safe place where you can park some very destrucive units(somthing like 14 rocketlauncher,and so...), then order a stomper to stomp next to that place, when the worm arrives, well, u can choose between sacrifin'the stomper, or letting him live...(a real harkonnen would enjoy killin the poor guy)
when the worms there launch the atomics(better launch it a bit before the worms arrrive) or order the force to strike hard.
but don't take a tea at this time because the worm would retreat fast! (normal,hu?).if u don't succeed at once, do it again. usualy, there's only one worm in a map... but if there's more(hard mode, or special missions), then u should strengthen ur defenses fisrt( the ennemy ain't as dumb as the worm!). goodluck
some buildings have a dirt part... so u don' need to put it on a complet concrete basement. this tip is usefull when u are short of room for building things and when u need cash for "more important" tasks(as tanks,MCVs...). but remember: all ur buildings ar stronger when built on concrete!
Build another refinery early in the game, wait for delivery of harvesters, then sell. You get two to four light infantry, and your refinery can service many harvesters. There is no need to build concrete for the refinery you sell.