I can't say for sure, but if you just want to kill it, wouldn't a broad-leaf weed killer do the trick?

They're tough to kill because they grow from an underground rhizome which spreads itself very quickly. Wait until the leaf is very large and then paint it with RoundUp. Don't spray because you'll kill the grass. Just use a cheap paintbrush.

The real question is, why did you replace plants with sod? A lawn is the most expensive landscape you can plant. Good luck.

Thanks for the tips. The reason we put down sod was because the entire yard looked like a rain forest, you literally couldn't see the house from the street. Plus we like to entertain and there was not one inch of the yard that was open enough for even a picnic table, let alone an area large enough for people to gather.