The Asiatic lily beetle (Lilioceris lilii) reached Miriam's Corner at least two years ago, perhaps three. I have a line of over 100 lilies that really attracts the critters. They are bright orange/red beetles about a third of an inch long (close-up photo and more info). You generally see them on the leaves of asiatic lilies; they do not affect daylilies.

Left alone to feed, they will defoliate lily plants, killing them. These pests are not widely distributed, but can be found in zones around where they were first accidently introduced. About a 30-mile area outside Boston is one such area. Another recent area of arrival is Oxford, England.

From my observations, it's not the beetles that do the major damage, but a larval stage that looks like a mound of black goo on the underside of the leaves. The critter itself is a very small slug in the middle of the goo. They eat the leaves starting near the bottom and a single slug can take out a plant in a few days. You can recognize their damage because parts of or the entire leaf are left as a semi-transparent reminder of the larva's passage. I pull off all affected leaves and squash the slug (yuk!). I think is it also effective to run your hand up the plant to knock the slugs off before they begin to eat.

The beetles are so visible that it's easy to pick them off, which I do 2-3 times per day in sunny weather. Cultivating the soil around the lilies early in the year helps a little, since the beetles seem to emerge from the ground. I have tested Safer Soap (mild insecticide) on the lilies which appear to be unhurt. The soap doesn't seem to affect the beetles, but does slow down the slugs. Since we are organic gardeners, chemical warfare is not the answer. (Editor's note: Safer Soap's packaging says specifically not for use on lilies.)

Despite the rampage of the beetles, I usually loose only a few plants entirely, but it does takes lots of patience. I've probably picked and squished a few hundred beetles this year and the slugs are just now getting into gear.