I wonder if they can find the native lilies out in the countryside.

If any are left.

These beetles seem to almost always only attack true lilies and fritillaria, and I am not familiar with the natives, so I don't know if they are Lilium species. Even if they are, I suppose that if they are somewhat rare or occur in small groups with a lot of separation from the other host plants, that they would not be in much danger. But I'm only guessing on that.

The local ones are Lilium columbianum and Fritillaria lanceolata (now with a different species name I am not remembering). I haven't seen any of the Lilium nearby in years, there even used to be a small patch visible along I-5 south of Seattle.

Everything goes for lilies, in the garden slugs and viruses in particular have been chronic problems for years.

bboy, my experience has been quite different. Recently I have been adding more and more lilies to my beds because they have always been pest free and easy, at least for the asiatics. They are the only ones I grow, as I don't care for the scent of the Orientals.

For the first time, this year I have had aphids on some of my lilies, but other than that, no problems with growing lilies for twenty some years. It makes me wonder if the aphid and beetle problems are interrelated, because IME aphids often attack weakened plants.

I did try some of the gorgeous martagons once, but I killed them. It was may fault, not theirs. I did have a virus once, but it clearly came in with some new bulbs and I just got rid of them and didn't replant in that bed for a few years.

I have a lot of lilies now, and have even gotten into propagating them recently, which is the main reason these beetles are such a disaster for me, but I have already decided to cull most of them and just keep my favorites and wait and see how much of a battle it is to manage these new pests.

Aphids transmit viruses. With garden plants in general there can be viruses present in stock that have a weakening effect without other obvious visual clues like streaking or deformity. For example, when ~35 kinds of viruses were cleared out of rhubarb stocks used for forcing in sheds to provide winter income in parts of Britain the size and productivity of the plants went way up. With lilies specifically it was said for years that you did not want to put forced Easter lilies out in the garden near other kinds as the L. longiflorum were likely to be virused. So these were looking and growing well enough to be sold yet were actually infected.

Aphids here attack garden plants with the most tender new growth available--the healthiest plants. The populations can boom and by the time it is noticed, the plant appears as "weakened". The new growth of prized plants is now checked every 2-3 days in the aphid high season.