What can I do to protect my lilies from lily leaf beetles?

A Question of the Week
Lily leaf beetles

Lily leaf beetles have been a menace since first arriving in Massachusetts in 1992. Native to Europe, the lily leaf beetle (LLB) is an especially damaging insect species that feeds primarily on true lilies (Lilium species, not daylilies). Native lilies such as Canada, Turk’s cap, and wood lilies, as well as a number of garden lilies and Fritillaries are susceptible to LLB. Hungry adults and larva will eat both the leaves and flowers on lilies, sometimes leaving only the stem behind.

Adult beetles are bright red with black legs, antennae, heads, and undersides. They overwinter in the soil or plant debris and emerge as adults in the spring. They are strong fliers and can travel considerable distances to find host plants. Once lilies start growing, LLB adults aren’t far behind. When adult beetles find a suitable host plant, they feed and mate. Females lay orange eggs in lines on leaf undersides, flower buds, and flowers. As soon as the eggs hatch, the larva begin feeding, all the while covering themselves with their own excrement to deter potential predators.

lily foliage that is showing early signs of LLB damage
Lily foliage showing early signs of LLB damage

If you only have a few lilies in your garden, hand-picking the adults, eggs, and larva is a good control measure. You can either crush the insects with your fingers or drop them into a soapy water solution, which will kill them quickly. Make sure to check the undersides of leaves for hiding insects and eggs. If you have a large number of lilies and hand-picking is impractical, some insecticides can provide effective control. Before using any pesticide product, always read the label and follow the directions closely. Contact the Infoline for specific insecticide recommendations.

Got questions? The Ask UNH Extension Infoline offers practical help finding answers for your home, yard, and garden questions. Call toll free at 1-877-398-4769, Monday to Friday, 9 a.m. to 2 p.m., or e-mail us at answers@unh.edu.