Yes, monkeys communicate, but they aren't talking like people do. Only parrots can do this so far, although limited.
About trees, they do not communicates or feel pain.
,,releasing pheromones to warn other trees, of their type, that a bug is eating them"
That makes no sense. Bugs and maggots are all time eating trees, so they must constantly releasing that, also it is pointless to even communicate since they cannot do anything about it. Trees do not have nerves, reflexes to react.
Certain types only like you said, mostly in Amazon, have sensors and move if you touch them, and release some pheromones, those are some specific plants. Those plants which eat bugs, waiting them to fly at them and grab them at high speed are also known to react