Viburnum Leaf Beetle in Wisconsin

The Viburnum Leaf Beetle (Pyrrhalta viburni) first arrived in southeastern Wisconsin around 2015 and, unfortunately, has established itself as a major pest on susceptible species of Viburnum. This imported pest is native to Europe and Asia and, as such, our native Viburnums have not had a chance to establish resistance and are especially vulnerable.

Viburnum Leaf Beetle feeds only on certain species of Viburnum. They can quickly skeletonize leaves and defoliate entire plantings. Most damage is done by the larval stage in spring and early summer, but the adult beetles will also feed on foliage from mid-summer through fall.

These beetles produce one generation per year. They overwinter as eggs in the Viburnum’s twigs and hatch in early May as tiny, light green/yellow larvae marked with rows of black dots. They begin feeding immediately on leaves. Due to their small size, you may notice damage before you see the insects. They grow through three developmental stages as larvae, molting, and growing larger at each stage.

They reach the final stage of larval development in June, crawl down the stems and burrow into the soil. They remain in the soil for 10-14 days and then emerge as adult beetles. The adult beetles are light brown in color and approximately ¼” to ½” in length. They will continue feeding on leaves through the summer months, causing skeletonization.

The female beetles will chew holes into the slender stems, lay their eggs in these crevices, and then seal the holes with a mixture of the chewed wood fiber. A single female can lay up to 500 eggs in a season. These sealed cavities protect the eggs overwinter. Then they emerge in spring to begin the cycle again.

A healthy Viburnum plant may survive significant defoliation for one season; however, severe beetle damage will likely weaken or kill the plant after several seasons.

Viburnum Leaf Beetle larvae stage from early May through June.

Viburnum Leaf Beetle adult stage from late June and beyond.

For now, avoid planting highly susceptible species of Viburnum.

Avoid highly susceptible species for now:

• Arrowwood Viburnum (Viburnum dentatum)
• European Cranberry Bush Viburnum (Viburnum opulus)
• American Cranberry Bush Viburnum (Viburnum trilobum)

Be cautious with moderately susceptible species:

• Mapleleaf Viburnum (Viburnum acerifolium)
• Witherod Viburnum (Viburnum cassinoides)
• Nannyberry Viburnum (Viburnum lentago)
• Blackhaw Viburnum (Viburnum prunifolium)

Consider resistant species:

• Koreanspice Viburnum (Viburnum carlesii)
• Siebold Viburnum (Viburnum sieboldii)
• Judd Viburnum (Viburnum x juddii)

Spice Island™ Koreanspice Viburnum (Viburnum carlesii ‘J.N. Select A’)

• Prune out and destroy egg-infested twigs. Egg masses appear in raised, oblong rows on the slender twig tips. Pruning these twigs out and burning or disposing of them will reduce beetle populations. Twig egg mass removal can take place anytime between October and April.
• Spray thoroughly with dormant/all-season horticultural oil in early spring before leaves emerge. This is a non-toxic oil spray that coats twigs and egg masses and kills them by smothering. A single thorough application of horticultural oil should eliminate up to 80% of the eggs. (Managing viburnum leaf beetles by Cornell University)
• Spray with contact insecticide during the larval stage (early May – mid-June). This young, soft-bodied larval stage makes contact insecticides highly effective. Make sure to spray thoroughly, including the underside of the leaves, to ensure contact. Organic options include Insecticidal Soap, Super Soap, Pyrethrin, and Captain Jack’s Deadbug (Spinosad). An effective chemical option is Bonide’s Eight insecticides.
• Spray with contact insecticide during the adult stage (July-October). This is less effective than spraying during the larval stage as the adult beetles are highly mobile and have harder bodies.

Note: Use of systemic insecticides – those applied to the soil and absorbed by the plant – isn’t recommended for spring application. This method may negatively affect beneficial pollinators visiting the plant’s flowers. Consider systemic insecticide only after the flowers fade.

Apply Horticultural oils in spring during larvae stage.

Learn more about Viburnum Leaf Beetle from these great local resources:

• UW-Wisconsin Horticulture article on Viburnum Leaf Beetle.