The lily leaf beetle was first introduced to Marathon County in 2014 and then spread to Portage County earlier this year. It was recently found in a lily garden in Merrill. The lily leaf beetle is native to Europe. It is believed that the beetles were introduced to Eastern United States in 1992 on a shipment of bulbs.
True to its name the lily leaf beetle lays eggs and feeds on true lilies (genus Lilium) and fritillaries (genus Fritillaria). True lilies include Asiatic, Oriental, Easter, Turk’s cap, and tiger lilies, as well as, native lilies such as the wood lily. The lily leaf beetle will not feed on canna lilies, calla lilies, or daylilies. They have been known to also feed on Solomon’s seal, bittersweet nightshade, potatoes, Hollyhocks, and Hostas. However, it appears they do not lay their eggs on these plants.
The adult lily leaf beetle has a red body with a black head, antennae, legs, and underside and is ¼ to ½ inch long. Females will lay up to 450 eggs in irregular strings on the underside of the leaves over two growing seasons sometimes over two growing seasons. The eggs hatch in one to two weeks. These orange to light green larvae will cover themselves with their excrement to repel predators. The larvae will feed for 16 to 24 days before burrowing into the soil to become a fluorescent orange pupa. After 16 to 22 days they emerge as adults. The adults will feed until fall and then overwinter in plant debris in protected areas that are shaded, cool, and moist. When the adults emerge in the spring they will mate and lay eggs. There is only one generation per year.
Both adults and the larvae feed on the leaves, stems, flower buds, and flowers. Most of the damage is caused by the larvae. There are no natural enemies for the lily leaf beetle. Some Oriental varieties appear to be resistant to beetle as where many if not all the Asiatic lily hybrids are susceptible. To control the lily leaf beetle non-chemically, look at the plants early in the morning and brush off the adults and larvae into a container of soapy water. Look on the undersides of the leaves for eggs and remove the leaf or crush the eggs. Insecticides that contain active ingredients such as permethrin, cyhalothrin, deltamethrin, pyrethrin control beetles that are present. Neem oil and insecticidal soaps also have some control on larvae. Several applications may need to take place as the beetles move from garden to garden. Caution should be used to ensure nontarget insects, including pollinators, are not present when applying all insecticides. Always read and follow labeled directions when making any pesticide application.
Please contact the Lincoln County UW-Extension Office at 715-539-1072 to report locations of the lily leaf beetles as we will be tracking their movement in the county.
For more information see the link to the University of Wisconsin Extension/Wisconsin Department of Agriculture Bulletin: Stop the Lily Leaf Beetle or by contacting Dan Marzu, Agricultural Educator, at 715-539-1072 or email@example.com.