Viburnum Leaf Beetle (Pyrrhalta viburni)

Question: Hello. I work at at a nature center in Kent County. Our native viburnums have been completely defoliated by a skeletonizing insect property-wide. I suspect that it's an outbreak of VLB. Wondering if someone could come out to confirm, and also looking for advice on managing this insect on a landscape scale.

responder: Thank you for your question!   Laura S.      Michigan State University Extension Advanced Master Gardener Volunteer You may also contact the toll free MSU Extension lawn and garden hotline at 1-888-678-3464 with your gardening questions or visit www.migarden.msu.edu for Smart Gardening resources. Replied June 14, 2023, 11:06 AM EDT
response: Hi Julie  Your pictures of the leaves are too far away and too blurry to tell if VLB is damaging them. If you would like to try again, lay out 3-5 leaves on a plain sheet of paper( no paper towels please) and take a picture from about 6 inches away.  VLB is managed before the damage starts, or when it is first noticed.  Here are details, along with pictures to compare with your shrubs. The pictures are taken when damage begins, not later after leaves have turned brown.  https://hort.extension.wisc.edu/articles/viburnum-leaf-beetle/  If you have a large number of viburnums for which to care, see this advice from Morton Arboretum: “The Morris Arboretum has a large collection of viburnums, including many native and non-native species. While VLB had already been observed in passing, this project included a thorough baseline survey of VLB damage throughout the Arboretum. Data were collected for the number of twigs infested with VLB, the number of cavities on each twig, and whether a wound response had been produced. This information was compared to existing evaluations of viburnum susceptibility based on defoliation, and previously unlisted species were evaluated.   In the future, VLB populations should be managed by annually clipping and destroying infested twigs between October and March. If this window is missed, young larvae can be sprayed with horticultural oil, and adults shaken off plants into soapy water. However, if regional VLB populations become denser in coming years, pest pressure will still continue to increase at the Arboretum, as beetles come from surrounding properties. Therefore, highly susceptible viburnums should be avoided in new plantings, and the understory of natural areas should be diversified. Pest pressure should be reevaluated every 3-5 years, with a repetition of the survey in this project.”

responder: The Question Asker Replied June 14, 2023, 12:14 PM EDT
response: Here are photos of less-damaged leaves. I manage 143 acres, most of it woods with Viburnums and dogwoods as the main understory shrubs, so garden-scale treatments are not going to be feasible.On Wed, Jun 14, 2023 at 11:08 AM Ask Extension <<personal data hidden>> wrote:

responder: Thank you for your question!   Laura S.      Michigan State University Extension Advanced Master Gardener Volunteer You may also contact the toll free MSU Extension lawn and garden hotline at 1-888-678-3464 with your gardening questions or visit www.migarden.msu.edu for Smart Gardening resources. Replied June 14, 2023, 12:34 PM EDT
response: Thank you for the new pictures. This looks like four lined plant bug damage. You may have damage from both pests. Here is what four lined plant bugs look like, along with treatment- https://extension.umn.edu/yard-and-garden-insects/four-lined-plant-bugs To get a second opinion, please email all your photos to <personal data hidden>   This is the MSU Plant and Pest Diagnostic lab. Regards, Laura