Lily leaf beetles continue to spread in Michigan

Lily leaf beetles continue to spread in Michigan

Monitor lilies throughout the growing season in Michigan for signs of lily leaf beetle larvae, feeding or egg damage.

Lily leaf beetle, also called scarlet lily beetle (Lilyoserus is nocturnal), is an invasive pest of increasing concern in North America. Adults and larvae cause significant nutritional damage to the leaves, stems and flowers of domestic, exotic and hybrid lily species (photo 1). The main hosts of lily leaf beetles are plants of the genus lily And Fritillaria. Ladybugs are commonly found on tiger lilies, Easter lilies, Asiatic and oriental lilies, and fescues, making them the most at risk for significant feeding damage. Minor feeding damage can also occur on lily of the valley (Councils of convalaria), Sulaiman's ring (Polygonatum S.), bittersweet (Solanum s.), potatoes (potato), marshmallow (Alsia) and different types of hosta. daylilies (Hemerocallis), calla lilies and canna lilies are not attacked by cochineal lily beetles.

Photo 2. Lily leaf beetle eggs are laid in succession and may be located near leaf fall. Photo by Bruce Watt, University of Maine, Bugwood.org.

life cycle

This insect spends the winter as an adult in the soil or leaf litter, and emerges in early spring until June to lay between 250 and 450 eggs. Eggs can be found on the underside of tulip or fescue leaves in three to 12 irregular lines (Image 2). The slug-like larvae hatch after one to two weeks and can feed for 16 to 24 days. Through larval development, these orange-green caterpillars cover themselves in their feces to deter predators (Image 3). Adults have one generation and live for several weeks before returning to the soil, often near lilies.

The larvae are covered in feces to deter predators.
Image 3. Caterpillars are covered in feces to deter predators. Photography by Richard A. Casagrande, University of Rhode Island, Bugwood.org.

distribution

The tulip leaf beetle was discovered native to Eurasia, initially in North America in Montreal, Canada, in the 1940s and in the United States in 1992. Movement of bulbs is the presumed way this insect spread between countries. The beetle spread rapidly across New England in the mid-to-late 1990s.

Researchers at the University of Rhode Island have developed a biological control program using a small parasite that parasitizes lily leaf beetle larvae and have successfully reduced the number of lily leaf beetles.

Unfortunately for the state of Michigan, lily leaf beetles were first found in 2016 in Jackson County. This insect's range has slowly increased, with 2022 being the year in which this insect preyed heavily on lilies across parts of southeastern Michigan, resulting in several reports being filed with Michigan State University Extension.

What's going on in Michigan?

Scientists at Michigan State University plan to implement a similar biological control program that was successful on the East Coast. To have the greatest impact, we must identify locations in Michigan where damage from this beetle is most severe. Gardeners who plant lilies are asked to report any findings of the scarlet lily beetle as well as photos of damage to plants to the Midwest Invasive Species Information Network. This data will be used to determine ideal locations for releasing parasitic wasps.

Management options

Since the scarlet lily beetle originates outside of North America, it has few natural enemies that are effective in controlling it. Hand-picking beetles from plants and crushing them or throwing them into a bucket of water may provide relief if only a few beetles are present. Contact insecticides are the only other option. Products containing permethrin, cyhalothrin, deltamethrin, pyrethrin, spinosad and other insecticides intended for ornamental use have been shown to be more effective in control. Azadiractin (neem oil) products and insecticidal soaps have also shown some control of small lily leaf beetle larvae. If using an insecticide on flowering plants, read the label to follow instructions and avoid exposure to pollinators.

Did you find this article useful?