I will guess that the ants are growing fungus as food for the ants to eat. You can kill the fungus with Serenade, Hydrogen Peroxide and Zero Tolerance safely and effectively. When the fungus does not grow I assume either the ants will die of starvation or move elsewhere.

ZT is hydrogen dioxide a stronger form of HPeroxide. Basically it is close to water but an oxident that is safe for humans. but dont spray yourself. it might burn the skin etc. but it is safe in the sense it is not a poison that is around once it dries up. after drying it is gone.

H2O is water
HO2 is a concentrated oxidizer hydrogen dioxide.
H2O2 is hydrogen peroxice an oxidizer

this stuff all breaks down into water and dries up.

Serenade is my favorite of the above.

Here is a link that might be useful: serenade on garden web

Thank you! I'll give that a try!

jennsnaturalgarden:

Lots of ants, sick plants? Do a Google search on watermelons-aphids. The ants are probably farming aphids, which sap the plants and also transmit disease. That disease could cause black leaves.

Aphids hit my muskmelon crop last year, the first in many when I did not have a good crop. I had such a large patch of melons, I decided chemical control was impossible, and ladybugs soon showed up in huge numbers, but the melons never recovered. I had my best watermelon crop ever, though.

So far this year, my muskmelons are doing great, and no sign of a return of the aphids. My watermelons, though, are doing nothing. Seem sickly, vines browning, leaves staying small. No signs of aphids. I suspect a soil-borne disease. It's always something.

Tom