On Aug 12, 6:19*pm, Joe wrote:
On Aug 12, 4:04*pm, "John Grabowski" wrote:

snip.
*It's mold and there is probably moisture behind the wall to support its
growth. *Most likely this has happened before, but the previous owners did a
good job of covering it up for the sale. *I would cut out the entire lower
section of the wall and see what's going on back there.

John's right. Get rid of the contaminated drywall. Then you need to
treat the wall cavities with mold proofing materials as recommended by
experts of your choice (Yellow Pages). Finally, install mold proof
drywall and future water incursions (hopefully minimized, as below)
won't cause mold problems.

Do you know why the basement flooded? *You will need to address that problem
as well. *You might want to consider consulting with several basement
waterproofing companies.

An essential step. Dry houses are healthy houses, with the added
benefit of a very important feature to offer a future buyer should the
OP need to move.

Joe

Thanks for the responses everyone.

The basement is flooding because there is a drain that is connected to
what I assume is a sewer line and it backed up due to extremely heavy
rainfalls.

In regards to identifying it, my landlord was trying to convince me
that it wasn't mold and that mold couldn't grow so quickly. I thought
she was wrong, but I couldn't say for sure.

Thanks for the advice.