In addition, the lichen has set out rhizomes beneath the leaf cover that surround the lure for 20 yards. Anyone approaching the lure must make two saves vs. death ray when approaching or retreating. A failed save indicates that a rhizome has been triggered. The rhizome flings a spore cyst into the air that explodes, doing ld8 points of damage to all within a 5' radius, but does not cause infestation.
Looks fine to me, though I'd be ok with cutting the secondary damage a bit (since it has a disease). Should we specify that the lure takes up a 5 ft square?
How about:
In addition, the main body of the plant is surrounded by rhizomes out to a 20 ft radius. If a creature enters this radius, a rhizome will reflexively fling an immature spore pod at the creature as a ranged touch attack with attack bonus +X. If the pod hits, the creature must make a DC X Fortitude save or suffer 1d6 Con damage.
I used the ranged touch to simulate the save in the original language.
I'd go with both Spot and Knowledge (nature) alternatives. The damage from this thing is pretty nasty, so maybe DC 20 to 25?
Changing "plant" to "fungus" is fine.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.