Posted: 20/07/2017 at 06:44
Start with clean compost.
When you spot the first lily beetle, early in the season, give them a spray of provado ultimate bug killer. This is systemic and lasts about eight weeks. I only use it early in the season. By the time the flowers come out it has worn off, as evidenced by plenty of hoverflies on my lilies. Squash all red beetles on sight. By this time there are a few nibbled leaves. If you see the nasty larvae encased in black faeces, wipe off with damp tissue.
When the flowers have finished, cut off the bit the with seed pods forming but leave the stalk with leaves on. At this point I am going to give them another spray , so the leaves can nourish the bulb for next year.
Provado will kill bees, so it has to be used carefully. I believe in this way, you can protect the other insects but get the lily beetles. It's not perfect, I have some nibbled leaves, but not the decimated stems I had before.
The idea method is inspect at least twice a day,crush all beetles on sight, wipe leaves regularly and have perfect plants. However if you have a job or any life at all, you won't have the time.