Lily leaf beetle: Watch out for this garden pest
Monitor lilies throughout Michigan’s growing season for signs of lily leaf beetle larvae, feeding damage or eggs. Take control measures if necessary.
The lily leaf beetle (Liliocerus lilii) is an invasive pest of growing concern in North America. The lily leaf beetle targets “true lilies” (genus: Lilium), however it has also been recorded on some other hosts. The larval form of this beetle causes significant feeding damage on the leaves of native and exotic lily species and hybrids.
Liliocerus lilii (in the family: Chrysomelidae), native to Europe and Euroasia, was discovered in Montreal, Canada, in the 1940s. It has since been transported to the United States in 1992, likely through moving bulbs, and continues to expand its range. It is currently prevalent in the north eastern U.S. and is continuing to spread towards the Midwest with recent reports of lily leaf beetle detection in central Wisconsin and eastern Iowa. As of 2016, there have been multiple reports in southeast Michigan’s Wayne County.
These bright red beetles overwinter as adults in the soil or leaf-litter, emerging in early spring and through June to lay eggs. Eggs can be found on the underside of lily or fritillary leaves in irregular lines of three to 12. The slug-like larvae hatch after one to two weeks, and can feed from 16 to 24 days. Through their larval development, these orange-green larvae cover themselves in their own frass (excrement) to deter predators.
The primary hosts for lily leaf beetles are plants in the genus Lilium and Fritillaria. They are commonly found on tiger lilies, Easter lilies, Asiatic and oriental lilies, and Fritillaries, making them the most at-risk for significant feeding damage. Minor feeding damage can also occur on lily of the valley (Convallaria majalis), soloman’s seal (Polygonatum sp.), bittersweet (Solanum sp.), potato (Solanum tuberosum), hollyhock (Alcea) and various hosta species. Daylilies (Hemerocallis) are not affected by this pest.
Contact insecticides can be used to control larval feeding on plant foliage. Products containing Permethrin, Cyhalothrin, Deltamethrin, Pyrethrin and other insecticides labeled for ornamental use have shown the most effective control. Systemic insecticide such as imidacloprid have reportedly provided effective control applied either as a foliage spray or soil drench depending on label instructions. Azadiractin (neem oil) products and insecticidal soaps have also shown some control of lily leaf beetles.
Hand-picking and destroying adult beetles, larvae and eggs is also effective in reducing damage.
As with any insecticide, only use products appropriately labeled for desired use and always read the label.
Although no native parasitoid of lily leaf beetle exists in the U.S., research is underway at the University of Rhode Island on potential biocontrol options.
Research on resistant lilies (ones that limit survival of lily leaf beetle eggs) from the University of Maine indicates Asiatic hybrids are the most susceptible lilies, while certain oriental lilies and other hybrids may provide some resistance. They state that the three most resistant lilies in their tests are Lilium henryi ‘Madame Butterfly’, Lilium speciosum ‘Uchida’ and Lilium ‘Black Beauty’.
Please be vigilant of this emerging pest and spread awareness amongst anyone who grows lilies in Michigan. Monitor lilies throughout the growing seasons for signs of larvae, feeding damage or eggs.
A map of lily leaf beetle reports is currently being curated by Naomi Cappuccino of Carleton University in Ontario, Canada. For more information on her ongoing research or to report a detection of lily leaf beetle infestation, visit her Lily Leaf Beetle Tracker website.
- Lily Leaf Beetle, University of Maine Extension bulletin #2450
- Invasion of American native lily populations by an alien beetle, Biological Invasions
- Potential novel hosts for the lily leaf beetle Lilioceris lilii Scopoli (Coleoptera: Chrysomelidae) in eastern North America, Ecological Entomology
- Biological control of the lily leaf beetle, Lilioceris lilii, in North America, University of Rhode Island