The Viburnum Leaf Beetle (VLB) is an invasive insect that has been recently detected in Dane County. There have been nearby infestations over the last 10-15 years that were successfully eradicated but we’re currently seeing a large active population make its way across southern Wisconsin. The VLB is found exclusively on viburnum shrubs beginning in spring.
Main Concern
Our landscapes typically become vulnerable when exposed to multiple stressors. Often, our trees and shrubs can recover from a single pest or stressor. The VLB can completely defoliate viburnum TWICE in a single season, weakening the shrub so thoroughly that it doesn’t recover.
Identifying VLB Damage
- VLB damage can be easily mistaken for Japanese Beetle damage because they both chew lacy, or skeleton-like patterns in leaves.
- Feeding is usually exclusive to the area between leaf veins.
Identifying VLB
- Young larae are green-ish yellow and are about 1 mm long.
- As they increase in size they appear more yellow-ish brown and develop black lines and spots on their bodies. Mature larvae are slightly larger than the beetle itself at about ⅓ inch long.
- Adults are a yellow-ish brown color and are approximately ¼ inch long.
- Locate egg laying sites by inspecting the underside of young branches. The presence of small brown-ish black bumps should be highly visible against the color of the shrub.
Protecting Shrubs From VLB
- When possible, avoid cranberrybush viburnum and arrowwood viburnum which are more susceptible to infestation.
- A properly-timed topical treatment to egg laying sites and larvae can dramatically reduce an infestation.
- In certain cases, systemic insecticides are an effective option.
- From fall until spring, examine viburnum twigs for egg laying sites. Any found should be removed and destroyed.
- Contact Lance Bright, your Certified Arborist to evaluate & protect your viburnum!
