Caren White is a Master Gardener and instructor at Home Gardeners School. She has been associated with Rutgers Gardens for over a decade.
Hey, what’s eating your lilies? Little red bugs? They must be lily leaf beetles.
What are Lily Leaf Beetles?
Lily Leaf Beetles (Lilioceris lilii) are also called scarlet lily beetles because of their bright red color. They are leaf beetles with a very particular appetite. They feast on the leaves, stems, flowers and even the buds of members of the lily family which include Oriental lilies, fritillaries, and North American native lilies such as Turk’s Cap lilies and wood lilies. They have also been known to chow down on Solomon’s seal, lily of the valley, flowering tobacco, hollyhocks, hostas and even potatoes. They do not eat day lilies which are not true lilies. Day lilies are Hemerocallis.
Lily leaf beetles are native to Europe and Asia. They were accidentally introduced into North America in 1943 in a shipment of bulbs in Montreal. From there, they spread throughout Canada. They were first spotted in the US in New England in 1992. In their native lands, the beetles have natural enemies which keep their population in check. They have no natural enemies in North America so they have spread widely and rapidly, decimating gardens wherever they have turned up.
Lily leaf beetles are small, about ¼ - 3/8 inches in length. Their upper bodies are bright red while underneath they are black. This helps them to hide from predators. When threatened, they hop off of the plant and land upside down on the soil beneath. Their black coloration blends in with the dark soil.
The adults hibernate over the winter in the soil or any plant debris not removed in the fall. They emerge in April when the lilies start to grow and begin to feed on nearby plants. They also mate at this time. The females lay up to 450 orange eggs in neat lines on the backs of lily leaves. The eggs hatch in 1 – 2 weeks. The larvae also feed on the leaves, stems, buds and flowers like the adults. To protect themselves from predators, they cover themselves in their own excrement. This is the time when you are most likely to spot them. After 2 – 3 weeks, the larvae drop off the plants on to the soil below. They burrow into the soil to pupate for an additional 2 – 3 weeks. Afterwards, they emerge as adult beetles which feed on your plants until the fall. Then they burrow into the soil or plant debris and hibernate during the winter, emerging in the spring to begin the cycle over again.
How to Get Rid of Lily Leaf Beetles
Keep them out of your garden
The best way to get rid of lily leaf beetles is to not allow them into your garden in the first place. Before you purchase new plants, check them over to make sure that they do not have any beetles or larvae on them. After purchase, quarantine them in another area of your yard for a week or two, keeping a close eye on them for beetles, larvae or damage from feeding insects.
Handpick the beetles and larvae from your plants
If you are not squeamish, a great organic way to get rid of lily leaf beetles is to pick the adults and the larvae off your plants. You can kill them by either squishing them between your fingers or by dropping them into a container of soapy water. Be sure to place a piece of paper or other light colored covering under your plants. Remember, the adults escape predators by dropping off of the plants and landing upside down so that their dark colored undersides blend in with the soil. By placing something light colored under your plants, it will make it easy to see them.
You might want to wear gloves if you are picking off the larvae. They cover themselves with their own excrement to make themselves repulsive to both their predators and gardeners. But at least they are easier to see than the tiny adults.
Use neem oil to kill them
Systemic insecticides can be used to kill any insects or larvae who feed on plants, but as an organic gardener, I stay away from toxic chemicals. I prefer to use neem oil. Start spraying your plants in the early spring every 5 to 7 days. Neem will kill the larvae as they hatch from the eggs as well as repel the adults, discouraging them from coming back to feed on your plants. Make sure that you are spraying the undersides of the leaves where the eggs and larvae are found as well as the rest of the plant to repel the adults.
Clean up your garden in the fall
Lily leaf beetles hibernate in plant debris, as well as in the soil, during the winter. Cleaning up any dead plant material, leaves, sticks and other debris from your garden in the fall will make your garden less attractive to the insects as a hibernation spot. Fewer beetles hibernating during the winter, means that fewer beetles will emerge in the spring to eat your plants and lay eggs.
Lily leaf beetles can quickly destroy your prized lilies and other plants. Fortunately, you can get rid of them safely and organically.
© 2020 Caren White