Red/Scarlet Lily Beetle

The Red or Scarlet lily beetle (Lilioceris lilii) is a small, bright red beetle that feeds almost exclusively on different species of true lilies (Lilium spp.) and fritillaria (Fritillaria spp.). This unfortunately also includes Saskatchewan’s provincial flower, the Western Red Lily (Lilium philadelphicum). It does not feed on daylilies (Hemerocallis spp.). If left unchecked, the damage can be severe as they feed on all parts of the plant. They have also been found on unrelated plants such as hostas, Solomon’s seal, Rose-Twisted stalk, potato, lily of the valley, hollyhock, and flowering tobacco, but only cause very minor damage and do not lay eggs on these hosts. 

The beetle originated in Asia and has become naturalized throughout Europe and Northern Africa. It was first identified in North America in Montreal, Quebec in 1943, and has since moved south and westward across Canada and the United States. It spreads by flying to new locations as it looks for new food sources, as well as through “hitchhiking” on plants as they are moved through greenhouses and purchased by unsuspecting gardeners. They have no natural predators in North America.

Adult beetles are approximately 0.5–1 cm long with a bright red thorax and abdomen (shell and back), and a black head, antennae, and legs. The underside of these beetles is also black, making them difficult to spot when camouflaged in soil and debris. Adult beetles startle easily and will drop from the leaves to the ground, landing upside down and staying completely still in hopes of camouflaging and escaping predation. Adult beetles can also make a shrill squeaking sound when squeezed and is thought to be a deterrent for birds and other predators. These beetles are strong flyers.

Larvae are plump and appear somewhat slug-like. They are usually dull orange, yellow, or brown. They cover their bodies in their black fecal matter (poop) as a form of deterrence and camouflage. From a distance they can look like bird droppings or dirt clumps. They begin feeding on the underside of the leaves and move on to the rest of the plant as the foliage is consumed. They are voracious eaters and are usually the most damaging stage of the pest.

Pupae are an intermediate form as the larvae transform into an adult beetle. Once the larvae have consumed enough food and are mature enough, usually after 2–3 weeks of feeding, they travel to the soil surface, burying themselves in a waterproof cocoon made of soil particles and their own saliva. They stay buried for 20-22 days, and then emerge as adult beetles, which immediately begin feeding.

Eggs are small, bright red to reddish orange, somewhat oval shaped, and found on the undersides of the leaves as well as on flower buds and open petals. They are usually laid in irregular lines of groups of 2-16 and are easy to spot in contrast to the green leaf.

Life Cycle

Starting in spring, as the first lily leaves begin to appear, adult beetles will emerge from overwintering and begin feeding and searching for a mate. After mating, females continue to feed for 2-3 weeks and then lay eggs. Eggs take an average of 6-10 days to hatch. Once the eggs hatch, the larvae feed for 2-3 weeks until mature. They then drop to the soil and spend another 2-3 weeks as pupae, transforming into an adult beetle. Once this metamorphosis is complete, usually around mid-summer, the new adult beetles emerge from the soil and begin feeding. They continue feeding until fall when they find a site to overwinter and continue the cycle the following year. Overwintering sites tend to be cool, shady and moist environments. Only one generation is produced per year, and adults can live for several years, with each female able to lay 205-450 eggs during her lifetime.

Both adults and larvae consume all parts of the host plant, creating irregular holes and notches in leaves, stems, and buds. If severe, the plant may be completely defoliated, and flowers may be irreversibly damaged. Larvae usually begin feeding on the undersides of leaves but will move to other parts as the leaves are consumed.

Physical

The most common and often most effective control method is simply hand-picking the beetles, larvae, or eggs, and squishing them. Monitoring and removing them as soon as possible is best, especially in early spring. If done consistently, handpicking can be effective control. If adults can be destroyed before mating and laying eggs, this can help decrease the pressure later in the season by interrupting their life cycle and decreasing the number of larvae present. Newly emerged buds and leaves are also very sensitive to damage, which can cause slow or abnormal growth, and so early control is ideal. Consistent monitoring is key as new beetles can fly long distances and move in quickly, especially if near other lily populations, as can be the case in a town or city.

Cultural

Most Asiatic-type lilies show high susceptibility to infestation and seem to be the beetles’ preferred food. Some Oriental-type lily varieties, such as ‘Uchida’ or ‘Defender Pink’ show resistance to predation. When purchasing new bulbs, consider trying some Oriental-types. Ensure they are hardy enough to survive in your Hardiness Zone (we are Zone 3b here in Saskatoon) and make sure there are no beetles already attached. More research and trials are needed to determine which varieties may be resistant to the beetle. If you have a lily that is resistant or unaffected, please let us know!

Gardener's Note: You may have to alter or update your garden layout to accommodate Oriental-type lilies as they tend to grow taller than their Asiatic cousins, but it may be a worthwhile compromise if the beetles are deterred from consuming them. They are also extremely fragrant!

Chemical

Insectecidal soaps and some horticultural oils have shown some efficacy when applied every 5–7 days after egg hatch. While these products can be effective, these soaps do not discriminate "good bugs" from " bad bugs", and so can be detrimental to benefical populations. As we always strive for chemical-free solutions at Gardening at USask, these products should be considered a "last resort", and are often no more effective than simply hand picking the beetles. 

Care must be always be taken taken when using these products. Always read and follow the label and instructions to keep yourself and your environment safe.

 

Biocontrols

Certain species of parasitic wasps have been shown to effectively control Red Lily Beetle populations, especially a species called Tetrastichus setifer. These tiny wasps only attack the lily beetles and do not sting humans. These wasps have been undergoing trials in Canada to see if they can control the lily beetle populations as well as survive our harsh winters. Tests have been successful in Ottawa, Ontario, Olds, Edmonton and Calgary, Alberta, and in Winnipeg, Manitoba. An initial trial was undertaken in Saskatoon in 2020–2021 but was unsuccessful due to the wasps being in poor health at the time of release. Work is ongoing to secure a new source of the wasps for additional trials but are currently unavailable for commercial or personal applications.

While this beetle can be quite devastating when left to its own devices, there are still many communities that do not have lily beetles. For these communities, the most important thing is not to bring contaminated plants into the region. If you do decide to plant lilies, always inspect them thoroughly and ensure the plants and bulbs are clean. This is good practice for any new plants, but especially important for managing this devastating pest.

References

Cappucino, N. (2021) Lily Leaf Beetle biological control. Lily Leaf Beetle Tracker. https://lilybeetletracker.weebly.com/biological-control.html

Cappucino, N. (2021) Lily Leaf Beetle life cycle. Lily Leaf Beetle Tracker. https://lilybeetletracker.weebly.com/lily-leaf-beetle-life-cycle.html

Fry, K. (2021) 2021 Lily Beetle Research Update. Olds College. https://www.oldscollege.ca/_media/2021-lily-research-update.pdf

Haye, T. (2000) Ökologische Studien zum Parasitoidenkomplex von Lilioceris lilii (Scop.) (Coleoptera: Chrysomelidae) an ausgewählten Mitteleuropäischen Standorten. Diploma Thesis, Christian-Albrechts-University, Kiel, Germany. Ecological studies on the parasitoid complex of Lilioceris lillii Scop Coleoptera Chrysomelidae in Central Europe.pdf 

Spears, L.R., Mull, A (2024). Lily Leaf Beetle (Lilioceris lilii). USU. https://extension.usu.edu/planthealth/research/lily-leaf-beetle 

Stack, P.A., Groden, E, Stack, L.B. (2024) Bulletin #2450, Lily Leaf Beetle - Cooperative Extension Publications - University of Maine Cooperative Extension. Cooperative Extension Publications. https://extension.umaine.edu/publications/2450e/

The Lily Beetle. (n.d.). Olds College of Agriculture and Technology. https://www.oldscollege.ca/smart-farm-research/areas-of-focus/faculty-led/the-lily-beetle.htm

Ernst, C. (2009) The Lily Leaf Beetle (Lilioceris lilii): an unwelcome invader. Lilies.org. https://ww.lilies.org/pdfs/lilybeetle.pdf