Seems okay. It should apply damage OnParticleSpawn. Is the whole thing firing? What are you trying to achieve?
And most importantly what is your damage + radius?
It happened to me that I forgot to set this (0 damage causes the “Any Damage” event to not trigger) and since you have the radius there as well it’s even worse.
Trying to add a splash damage to a hitscan weapon, the effect is spawned, but the damage does not fire.
The default value of Damage+Radius is 400 should be large enough right?
You need an Event Generator module inside your particle. Just tested it with a sample blueprint and found that without it the OnParticleSpawn event doesn’t fire. Make sure you specify the type of event as Spawn and set the Frequency.
Still i’snt working for some reason The effect template I am using has multiple emitters, could that effect the trigger in some way?
The particle that I used for this had multiple emitters as well, so it shouldn’t be a problem. The event generator will create an OnParticleSpawned event for every particle that that particular emitter spawns (if you set the frequency to 1). So for example if you have a particle that has a flame emitter and a smoke emitter and you want the event to fire every time a smoke particle gets spawned, then you need to put the event generator into the smoke emitter and use the settings that I used. Make sure, that the emitter that has the event generator in it actually spawns particles.
Here is a picture of the whole system as I have it set up:
As you can see, the event is firing perfectly.
Thank you!, It still isn’t triggering, and I have to go. but I will check through it again soon.
Alright, that’s weird, but keep us updated! 
Alright I am back. I added a print string to the OnParticleSpawn event, and it is not printing when the effect is caused. So It is not the damage but the event that is the issue.
Ok here is as it stands: I am receiving no Prints when the effect is spawned, nor am I triggering damage.
Hey again,
set the type of the event from Any to Spawn… Don’t think that’s the issue, but it might help. What is the spawn rate of the mushroom emitter set to? How many particles does it spawn?
I tried to replicate the issue. I set my spawn rate to 1 and emitter loops to 1 and the particle doesn’t spawn and doesn’t create an event. It’s a bit weird. When I set the spawn rate to 2 I get 1 particle spawned and the event fires once. Maybe try to increase your spawn rate a bit?
Lovely issue with the UT creator is crashing on map load. Gotta wait until that is fixed 
Solve that issue, I need to play an online game of UT to get the Creator working
I came here because I had the same problem as the creator. I’ll leave my solution here, and hope it’s helpful for someone:
Making an array with “self” and connecting it to the “ignore actors” pin of the radial damage solved it for me. If this is done, every actor in the radius receives the damage taken events. if not, I do not get any events at all.
Seen the answer from btengelh, will install UE4 again and try it. Give me a day. Thank you for posting despite the age of the question!