Destroying a Particle with trail effect the trail isn't destroyed.

I created a fireball (particle system) and a trail(particle system) as a child to the fireball. In my game when i shoot,the destroyes itself after a short time or if it collides to something is gets destroyed. Although the trail doesn't and continues it's direction. I thought that when a parent is destroyed , the child object is also destroyed. Why isn't this happening and how can i destroy the trail without much effort. This hsa happened to me to few other similar particles i created. (ex. a ball with a trail particle)