I suspect you are looking for corn gluten meal
I think it is a pre-emergent weed preventer

Here is some info I found on dirtdoctor.com. There are also posts in other forums on gardenweb about its use:

Horticultural cornmeal or whole ground cornmeal is the natural disease fighter that is especially good for use on fungal diseases. ItÂs also good to use for cleaning up algae in ponds. Corn gluten meal is the natural "weed and feed" product. It is the protein portion of cornmeal.
Much of the cornmeal at the grocery store is just the starchy inside of the corn kernel and not effective for any of the plant uses.

I was hoping to incorporate it in my garden this year as I had several different plants get dark spots on them.

Preen makes an organic form of pre-emergent herbicide which is made from gluten. Look for the regular Preen and the organic version should be right there.

Diana Lynn