What's the best way to kill poison ivy without destroying other plant?

Round Up should help.

Is it the RoundUp specifically designed to kill poison ivy and its ilk?

Do not use Round Up. It is the most toxic weed killer known to man. It is poisoning the earth. If you want to kill poison ivy safely, mix equal parts of bleach and water in a spray bottle and spray it directly on the plant. Spray it on every ivy plant you see popping up and you will eventually kill it all. You have to be persistent in spraying it and it will pay off.

Roundup has now been proven to be a carcinogen besides poisoning the Earth. Stay as far away from that stuff as you possibly can!!

3 cups white vinegar

1/2 cup table salt

1 tablespoon liquid detergent or soap (I use Dawn) for stick-to-itiveness.

Directions

1. Mix vinegar and salt until the salt is completely dissolved. Stir in liquid dish soap, and pour into a spray bottle.
2. Spray onto the green growing leaves of the plants.
3. Wait a week, then repeat on any survivors. Best time to apply: during a dry spell.