How to Combine Poison Effects with the Barrage Ability?

[Zergy]

So I tried combining Barrage and a slow Poison effect, but every time I purchased Slow Poison (As a custom upgrade) It over ride the Barrage ability. Making my unit only shoot 1 target instead of 3. So how do I combine the Barrage ability with any Poison effects?

 

[Uncle]

You trigger the effects yourself using a Damage Engine or the Damage events. You can find a lot of posts about this topic.