I always lop off the spent flower stalks from my Filamentosas and Recurvifolias with no ill effects. The yuccas just keep doing their thing as if nothing happened. I have the aforementioned species as well as a couple of smaller Rostratas. I've been MOST FORTUNATE in having no trouble whatsoever from yucca bugs or any other pests or diseases that affect yuccas. The only maintenance I perform on them is a late fall trim of dead leaves and an early spring follow-up trimming off of leaves that the winter takes out.

I can't do much with them in the summer due to the mosquitoes, which really are a misery here since all the weather knows how to do is rain.

That's what Climate Change means to me. Not more heat. Not more cold. Just rain, rain, rain. Five days straight without rain? Impossible now. I guess it's better than droughts, but there is a price to pay for it.