If you love lilies in your garden, you may be plagued by a gardening nightmare: lily beetles are devouring Michigan lilies. They say you need to know your enemy. If you want to get rid of them, here are some things you need to know about them.
The lily beetle is also known as the scarlet lily beetle because of its vibrant scarlet color. Lily beetles primarily feed on certain lilies, but they also feed on other plants that are popular in Michigan gardens. According to Michigan State University, lily beetles feed on the stems, leaves, and flowers. In other words, they eat everything above ground on the lily. According to Michigan State University, “The beetle is commonly found on tiger lilies, trumpet lilies, Asiatic lilies, Oriental lilies, and elm lilies, so these plants are at highest risk for major feeding damage. Lily of the valley, Solomon's seal, wormwood, potato, hollyhock, and various hostas can also experience minor feeding damage.”
An adult lily leaf beetle feeding on a lily leaf. (Photo by Marianna Szucs/MSU)
Marianna Zucks, an assistant professor in the MSU Department of Entomology, says Michigan has seen an explosion in lily beetle populations in 2021 and 2022. The beetles came from Europe and were first spotted in Massachusetts in 1992, Zucks said. The beetles became a big problem in the Northeast in the early 2000s. The lily beetle was first spotted in Michigan in 2016.
Lily leaf beetle observations as of May 30, 2024 (Source: Midwest Invasive Species Information Network)
Schukes calls the lily beetle an “excellent disperser,” meaning it can move and spread quickly over a wide area. The beetle has now spread as far north as the Petoskey area. Schukes speculates that the northernmost reports of the beetle were probably carried on lilies that were brought in from southern Michigan.
In fact, the beetles have become such a problem that Schukes says they ate the lilies in his garden last year.
Szucs recommends knowing the beetle's life cycle, as that's the only way you'll know how to get rid of them in your garden. Currently, it's believed that lily beetles only have one generation per year, meaning adult beetles only breed once per season, laying eggs that hatch into larvae.
The most important thing to remember when it comes to getting rid of flower beetles is that these insects have different developmental stages: there can be eggs, larvae, and adults ready to hatch all at the same time, meaning new beetles are constantly hatching and developing throughout the gardening season.
MSU lists a variety of insecticides that will kill lily leaf beetles: Many insecticides are effective, but they do not kill the unhatched larvae inside the eggs.
So, Szucs' key advice is that they need to be controlled with weekly insecticide applications throughout the growing season. These garden monsters are not something you can get rid of in one go – just one application of insecticide will cause any new eggs that hatch to turn into hungry larvae within a week or two.
Many gardeners feel they cannot control lily beetles because of the many changing stages of this insect.
The MSU article “Lily Beetles Continue to Spread in Michigan” states, “Because red lily beetles are native to outside of North America, they have few effective natural predators. Picking the beetles from the plant by hand and crushing or tossing them in a bucket of water may be effective if there are only a few. Contact insecticides are the only option. Products containing permethrin, cyhalothrin, deltamethrin, pyrethrins, spinosad, and other insecticides labeled for ornamental use have been the most effective control. Azadirachtin (neem oil) products and insecticidal soaps also have some effect in controlling lily beetle larvae. If you use insecticides on flowering plants, read the label and follow the directions to avoid contact with pollinators.”
But remember, the eggs will constantly hatch, so you'll have to continue treatment every week. Most insecticides have limitations on how many times they can be used during the growing season, so you should read the insecticide label carefully.
Szucs and her research assistants are tracking the movements of the lily beetles and developing biological control methods for the insects. She wants us to dump any lily beetles we find in our yards at these three locations. She will use our beetles in a biological control method that has worked for her in the East.
