The photo is too out of focus for me to tell but the mention of ants leads me to believe that Aphids are the issue.

You can simply rub them off, spray them off with water. The next step is probably insecticidal soap which is simply soapy water. you can buy it in any garden center or make your own. But not just any kind of soap works. If you use insecticidal soap, just spray down the affected parts of the plant thoroughly and then wait several hours and spray it again with water. The soap kills the aphids. The next step is a chemical insecticide.

You can start with the least aggressive method and work up until you find a solution or go straight for carpet bombing with Sevin dust.
Bruce

I have always used soap solutions for controlling soft bodied insects like aphids. You can find some guidelines here:
http://www.ext.colostate.edu/pubs/insect/05547.html/

Bruce's advise is good.

I usually use insecticidal soap. Note: soap isn't the same thing as detergent (like most dishwashing liquids).

Drench them, let it set, and rinse. Don't apply in direct strong light.