Multiattack

The mangrove treant makes two slam attacks.

Slam

Melee Weapon Attack: +8 to hit, reach 10 ft., one target. Hit: 18 (3d8 + 5) bludgeoning damage.

Mangrove Mosquitos

The mangrove treant calls a swarm of mosquitos from its branches. The swarm of mosquitos uses the statistics of a swarm of insects, except it has a flying speed of 30 feet. The swarm acts an ally of the treant and obeys its spoken commands. The swarm remains for 1 day, until the treant dies, or until the treant dismisses it as a bonus action. The treant can have only one swarm of mosquitos at a time. If it calls another, the previous swarm disperses.