Oriental and Asiatic lilies are stunning stars of our summer gardens with their big, trumpet-shaped, fragrant flowers. These and other lilies (grown from bulbs) are under attack here from a small, colorful beetle — the scarlet lily leaf beetle.

Not to be mistaken for ladybugs, the scarlet lily leaf beetle is about a half-inch long with a very bright, solid red body, and black legs, head, antennae and undersurface. They live out their life stages on lilies, and both the immature stage and adults cause damage by eating the leaves and buds. Adults and larvae are commonly found together devouring lily foliage, and if undisturbed they will consume all the leaves leaving only bare stems. The insects are native to Europe, but came to this continent around 1945, possibly among a shipment of flower bulbs.

These Orienpet lilies put on a grand show every summer, but not without lots of work and observation removing scarlet lily leaf beetles which would devour them if left to their own devices. Photo by Lynette Walther.

First encountered in Canada, the beetles have since spread their range and are commonly here. According to the University of Massachusetts’ Center for Agriculture, Food and the Environment, the lily leaf beetle (Lilioceris lilii) feeds on, lays its eggs and develops on true lilies, Lilium species — Turk’s cap lilies, tiger lilies, Easter lilies, Asiatic and Oriental lilies but not daylilies — and fritillaria (Fritillaria).

The Center’s website states, “Although lilies and fritillaria are the primary hosts, lily leaf beetle also feeds, sometimes just lightly, on a number of other plants, including lily of the valley (Convallaria majalis), soloman’s seal (Polygonatum), bittersweet (Solanum.), potato (Solanum tuberosum), hollyhock (Alcea) and various hosta species. It is, however, a devastating pest to true lilies.”

The beetles emerge in early spring as foliage sprouts. They begin feeding at that time eating lily foliage and buds, laying eggs in May. The eggs look like tan-colored lines, turn orange, then bright red and hatch within four to eight days. The larval stage look like plump orange, brown, yellow or even green slugs with black heads. At first the young larvae initially feed on the undersides of the foliage but eventually will move to the upper surfaces and the buds. It is important to check both sides of foliage to remove them. As they feed they accumulate their excrement on their backs which makes them appear to be small piles of slimy black feces. Yeah, ick.

The feeding process continues. Larvae feed for approximately two to three weeks and then drop to the ground where they pupate. In about two weeks, the adults will emerge from the ground and soon begin feeding on your lilies again. They will spend the winter in the soil or plant debris in cool, shaded and moist areas, though not necessarily near the lilies. In the spring the cycle begins anew with females laying 250 to 400 eggs.

That means diligence is necessary and it must last all season if you want to reduce the damage these pests cause. Young larvae can be controlled with Neem products applied every five to seven days after the eggs hatch. I will often snip off the entire leaf when I spot the larvae to dispose of it.

The adults are able fliers, and will usually drop to the ground when approached for capture. Starting early in the spring, I start hand picking the adult red beetles, but I have to be quick and stealthy to catch them. Once caught, I simply smash them. They do not bite, nor sting. Another tactic is to slip a jar of soapy water underneath them to catch them as they fall.

According to the University of Massachusetts’ Center, there have been some efforts to combat the beetles with natural controls and parasites with limited success due to the parasites not surviving winters here.

So, it’s up to us to keep our beloved lilies healthy and blooming to enjoy for years to come.