EAST LANSING, Mich. (WOWO) — Michigan State University researchers have released more than 4,400 tiny parasitoid wasps at sites across Michigan in an effort to control an invasive beetle that can rapidly destroy lilies.
The project is Michigan’s first biological control program specifically targeting the scarlet lily beetle, an invasive species that attacks both cultivated and native lilies according to News10 Lansing.
Marianna Szűcs, an associate professor in MSU’s Department of Entomology, is leading the effort. Researchers released the wasps this year at 13 locations, including sites around Lansing, Ann Arbor, Mason and the Detroit metropolitan area.
The goal is to establish a natural predator that can reduce scarlet lily beetle populations without relying solely on chemical treatments.
The parasitoid wasps are native to Europe, where the scarlet lily beetle originated. Before releasing them in Michigan, researchers extensively tested the wasps to determine whether they would attack other insects.
Szűcs told News 10 that the wasps are highly specialized and target lily beetle larvae.
“They can really attack only little beetles. They won’t attack anything else on your landscape. And so they are very specialized wasps and parasitoids,” Szűcs said.
The wasps attack the beetles while they are still in their larval stage. The parasitoids develop inside the larvae, preventing the beetles from reaching adulthood and reproducing.
Researchers say controlling the invasive beetle could have implications beyond ornamental gardens.
Michigan is home to native lily species, including the Michigan lily and Canada lily, that can also be damaged by the scarlet lily beetle.
Szűcs said the insects can feed on native lilies and warned that severe infestations could threaten some native plant populations.
“These beetles can eat those native lilies,” Szűcs said, adding that “there are native species that these species could eradicate, essentially.”
Some of the wasp release sites are located in residential yards, where volunteers are helping researchers track the progress of the biological control effort.
Volunteers organized through the North American Lily Society have planted what researchers describe as “sacrificial” lilies. The plants provide a food source for the beetles while giving researchers a place to monitor both the invasive insects and the newly released parasitoids.
The researchers caution that homeowners should not expect an immediate reduction in beetles.
It could take years to determine whether the program is successful.
For the parasitoids to have a meaningful impact, they first have to survive Michigan’s winter, reproduce and establish sustainable populations. Researchers will then need to determine whether those populations are capable of suppressing scarlet lily beetle numbers over the long term.
Szűcs said homeowners who want to help the effort may actually need to tolerate some damage to their lilies.
“If people want to hang onto their lilies, lots of people just dig up their bulbs because they don’t like to see them being attacked,” Szűcs told News 10. “But if you leave them in your garden, it might look unsightly, but it may provide the resources for the parasitoids to establish.”
The Michigan effort builds on decades of biological control research in New England, where researchers have previously released similar parasitoid wasps to combat scarlet lily beetles.
Those programs have helped reduce lily beetle populations in areas where the parasitoids successfully established themselves.
The MSU researchers are now watching to see whether the same approach can work in Michigan.
The scarlet lily beetle can be particularly destructive because both adult beetles and their larvae feed on lily plants. Heavy infestations can leave plants severely damaged or stripped of foliage.
Rather than attempting to eliminate the beetle through repeated treatment, biological control seeks to introduce a natural enemy capable of keeping the invasive species in check.
Researchers say the wasps selected for the Michigan program underwent extensive evaluation before being released, with a focus on making sure they would specifically target the invasive lily beetle.
The project represents a long-term effort rather than a quick fix. Researchers will monitor the release sites in the coming years to determine whether the wasps survive, reproduce and spread sufficiently to establish a lasting biological control.
If they do, the tiny insects could eventually provide a natural defense for Michigan’s gardens and native lilies against an invasive beetle that has proven difficult for homeowners to control.
