Hi Chris
I am sure there are a few things one can use, but I have been using Potasium Permanganate. I make a rather strong mixture about 2 teaspoons to 40 lt water and then place them in there for about an hour. Make sure you also submerge the plants a few times to cover all areas.
I have heard some guys also do a dimmilin treatment but I suppose it depends where the lillys come from.
Best of luck