I have a purple coneflower which has been attacked by dotter - it looks like orange silly string with small white flowers and strangles the host plant. I've been taking it off as I see it but it keeps coming back. The little I can find on it says the only way to eradicate this is to cut the host plant to the ground. Will it come back this season? Has anyone had experience with this problem? I have several healthy coneflowers nearby - could it spread?