It is my understanding that lilies use their foliage to restore the bulb for next year's growth, but you might be O.K.because they are really very hardy. What I do know is that there are no treatments (chemical or otherwise) for red lily beetle because they are foreign to our areas and have no predators here. The way to get rid of them is to catch the little buggers and squish them - my favourite way is against a rock. If you are squeamish, you can knock them off the leaves into a bowl of soapy water and that will do them in too. The 'black poop' to which you referred is their eggs, and if you examine it closely you will see little red larvae in it. That should be removed. I do it with my hands by running my hands upwards over the stalk. If you are squeamish about this, try doing it with a light cotton glove. To control these beetles, you must examine your lily plants daily and hunt them down. Another thing that works for me (picked it up at a flower show) is to spray the emerging plants when they are just poking through the soil, and surrounding earth (that's where they overwinter) with a 10% solution of household ammonia in the early spring. The ammonia will not hurt the plants. That has helped me control them and I have never had to cut any of my plants down. Good luck!!