Plenty of snail species of canaliculata complex will actually eat plants aside from Marisa cornuarietis and hybrid Asolene spixi, not just the Pomacea canaliculata itself.there are two snails in the apple snail family that i know of that eat plants. cana snails and marisa snails. both are quite a bit larger than your average pest snail. the cana gets bigger than a golf ball, and the marisa snail looks like a giant ramshorn.
here's a great link for apple snail info, if it interests you: http://www.applesnail.net/
In my experience, MTS do not eat healthy plants but like most snails, they prefer dead to decaying vegetation. They are nocturnal preferring to appear in the dark mostly.