Hiya Jeffd yes I have used NEMASYS for ants in lawns. As I understand it, it DOES kill ants. They are nematodes that attack ants.
Lavendarlass, ants on plants are usually there because aphids are present too, ants harvest aphids. Spray or rub off aphids and your ants should disappear. Ants seem persistent near my front door and I put down ant killer several times but I find the hosepipe to be the best solution. It seems to affect the ants for a few days but then come back again, so I use hose again. I think this must be the worst season for ants