Posted: 16/06/2014 at 01:39
The larvae have already hatched and are munching away at your lilies right now!
The gunge is actually their poo which they cover themselves with after digesting the lily leaves they are eating (I know, disgusting little devils aren't they?!) If left, they can completely strip all the leaves in just a few days.
If you don't mind using chemicals, you could spray them all with Provado Ultimate Bug Killer, which is a systemic insecticide which will be absorbed into the lily plants and will kill them in short order. Unfortunately, it is toxic to all insects including bees, so if you have to resort to using it, make sure to read the instructions on the spray carefully and try to ensure it only goes on your lilies (bees aren't that keen on lily flowers anyway, so the risk of harming them is relatively low.)