While Illager Beasts can already destroy leaves and crops, it might be expected from most players that beasts can destroy other plant life too. However this isn't the case.

Tested with:

Lilypads

Vines

All flowers (wither rose might be WAI)

Cacti (might be WAI)

Grass, its variants, and dead bush

Coral fans (living and dead)

(Not tall) Mushrooms

Sugar cane

Kelp