I have sooty black stuff on one of my tomatoes. I seperated it and want to know how to get rid of the disease?

look for aphids.... their excrement is sweet and tends to mold quickly, hence the black stuff on the leaves..... to be rid of aphids, first wash off as many as possible with a sharp spray from the garden hose..... then treat the tomatoes to some Insecticidal Soap spray..... NOT dish soap, but the 'right' soap solution, sold just for this problem.... otherwise, you're endangering the plant and your future 'mater sammiches!!!...

once you spray every aphid you see, then maybe fifteen minutes to a half hour later, gently rinse off the dead bugs and take the soapy stuff off the plants with the rinse..... now wait three days, go look again and if you see more aphids, that means the eggs laid by the first batch have now hatched and you'll need to do the rinse, spray , rinse thing again.... then check again in a few days.... keep it up until you have to HUNT to find an aphid!!.... they prefer the new, tender growth, so look there first... also check under the leaves and in the leaf nodes for eggs....

here's some aphid info....

http://www.ces.ncsu.edu/chatham/ag/SustAg/aphid.ht...

http://www.na.fs.fed.us/spfo/pubs/howtos/ht_sooty/...

if you don't find the bugs on your plants, read here for other causes of the black leaf thing....

http://www.google.com/search?q=aphids&hl=en&prmd=i...

Hard to say without an image, but it sounds like black leaf mold. If so, you need to destroy the plant - put it in a tied bag and place it in the garbage.

I would also aggressively treat any other nightshades with an antifungal. Habanero and clove decoction would be a good homemade option; bordeaux mixture if you can get it.

The fungus can be caused from water splattering on the tomatoes.

And they need air flow and sun.

bug infestation aphids

soap & water spray