Plecos will tend to munch on any broad-leaf plant. Even the small Bristlenose plecos can tear up a plant, although they are small enough that the damage is often minimal. Feeding more heavily may help, but it's never helped me once a pleco developed a taste for a specific plant!
Plants that are considered "pleco-resistant" include the Anubias and Java ferns. Sometimes they will not bother small-leaf stem plants like Rotalia indica or very narrow-leaf plants like dwarf sagittaria. Plants that seem at highest risk of getting munched include, but are not limited to swords, crypts, and aponogeton.