Lily leaf beetle spreading in Wisconsin: The lily leaf beetle (LLB), Lilioceris lilii, is a small, bright red beetle native to Europe and Eurasia; it is believed to have arrived in the U.S. via lily bulbs shipped from Europe. Since LLB is not a U.S. native, it has no natural enemies, which assists in its spread. It was first detected in Wisconsin in 2014 in Marathon County, but has now spread to nine other counties including Wood, Portage, Shawano, Langlade, Lincoln, Oneida, Taylor, Door and recently, Dane County. The adult beetle, though small (¼ to ½ inch long) is very visible: it is bright scarlet-red with a black head, antennae, legs and underside. Adult females lay eggs mostly on two members of the lily family: true lilies (genus Lilium) and fritillaries (genus Fritillaria). True lilies include Asiatic, Oriental, Easter, Turk’s cap, Orienpet, trumpet and tiger lilies, as well as native lilies such as the wood lily. True lilies don’t include canna lilies, calla lilies, or daylilies. LLB feeds on lilies and fritillaries primarily, but they also feed on Solomon’s seal and flowering tobacco plants (genus Polygonatum and genus Nicotiana). Asiatic lily hybrids appear to be most susceptible to LLB, but some Oriental varieties seem resistant. The insect overwinters as an adult in soil near the plants it feeds on and emerges early spring through June. Females can lay up to 450 eggs on the underside of lily or fritillaria leaves. The orange to light green larvae appear slug-like, and cover themselves with their own feces to make them less appealing to predators. The larvae feed for 16-24 days, then pupate in the soil. The fluorescent orange pupae emerge as adult beetles in 16-22 days. LLB can be controlled via a variety of organic methods. These include hand-picking the insects and depositing them into a bucket of soapy water, using insecticidal soap and neem oil. Caution should be taken when applying the soap or oil during very hot weather due to potential phytotoxicity.
Other traditional contact insecticides include products containing permethrin, pyrethrins, cyhalothrin, or deltamethrin. Follow all label instructions as required by law.
If you think you have found lily leaf beetle, submit a sample to PJ Liesch at the Insect Diagnostic Lab on the UW-Madison campus or contact Liz Meils at the state Department of Agriculture, Trade and Consumer Protection (DATCP) as the spread of this insect is being tracked. The email at DATCP is DATCPNursery@wisconsin.gov. You can also contact your local UW-Extension office.