Any fresh vegetable should be good bait when trapping a woodchuck, but what seems to work really well is a cantaloupe cut into 2-inch-square pieces. As an added attraction, its juice can be drizzled all over the cage and the area around it.
When they emerge from their winter hibernation in the spring, woodchucks are eager to fill up on whatever they can find, and they do not much care about destroying a backyard along the way. As for catching them with a cantaloupe, one need not worry about cleaning out the trap if the little critter is not caught within the first few days. Woodchucks appear to like the fruit more as it decomposes.