Worms can be annoying, especially at the start of the game when you want to harvest plenty of spice. They simply eat up your harvesters. A very effective solution for this is to create a group of Troopers (five to ten should be sufficient). Worms are very vulnerable to missile attacks, and do not survive very long. Better yet, they are not very inclined to surface and chew up infantry. Put some Troopers around your spice-rich area, and let them do their work. Put them on some rocks if available. They will shoot up the worm and kill it in no time, allowing your harvesters to continue their work without disturbance. A few Rocket Turrets or Missile Launchers also helps.