The viburnum leaf beetle was first reported in North America (from Europe) in Ontario in 1947 and has subsequently spread (Johnson and Lyon, 1991). According to MA Department of Agricultural Resources records, the viburnum leaf beetle was first detected in Berkshire County, MA in 2004. Since then, it has been detected in Berkshire, Bristol, Franklin, Hampshire, Middlesex, Norfolk, Essex, Suffolk, Plymouth, Barnstable, and Worcester counties by state, federal, and university partners. By 2008, the insect was considered to be present state wide in Massachusetts. Citizen scientist reports (considered to be research grade) indicate that the insect has been detected in every MA county except Hampden County as of 2023. However, it is very likely to be present (just undetected) in Hampden County as well (Dr. Jennifer Forman Orth, MA Department of Agricultural Resources, Personal Communication).
The viburnum leaf beetle overwinters as an egg inserted into the twig of its hosts. Eggs are small and inserted into holes chewed into twigs and are visible due to the coating of chewed twig and excrement that the female fills each hole with, giving the twig a rough appearance. Several eggs (approx. 8) are deposited by the female into each hole. The coating/cap over the eggs provides them with protection from predators and possibly winter insulation as well. Each female may lay up to 500 eggs spread across many egg laying sites. When eggs hatch around May, the young larvae are approximately 1 mm in length and greenish-yellow in color. They may also be off-white and they lack spots. Larger larvae may appear yellowish-brown or green with black spots and may grow up to ½ inch in length. Larvae may be found anywhere on the leaves and usually in groups. When young, larvae feed on the undersides of the leaves. As they grow larger, they may feed on the upper surface. Larval development may take approximately 8-10 weeks to complete and 3 larval instars are reported. Pupae are yellowish and are found in the soil beneath the host plant. Adults emerge around the middle of July and are brown, smaller than the largest larvae (approximately ¼ inch), and will also feed on the leaves. Adults are present in the landscape until the first hard frost.
For a full list of viburnum susceptibility to this pest, visit: http://www.hort.cornell.edu/vlb/suscept.html .
Viburnum leaf beetle larvae and adults feed heavily on the foliage of the aforementioned host plants. Plants may be heavily attacked and have every single leaf skeletonized by this pest. Feeding is almost exclusively in the areas between the leaf veins. Young larvae begin by feeding in groups on the undersides of host plant leaves, typically on the lower branches of the plant. A heavily infested host plant may be completely defoliated by these insects. Adults feed on the leaves, but their feeding damage looks different from that of the larvae. Adults chew irregular and circular or oblong oval holes in the leaves. Because adults can fly, it is possible to notice adult feeding damage on susceptible host plants beginning by approximately late June on plants that did not previously have damage from feeding larvae. (They can move to a new planting beyond where the eggs overwintered.)
Visually monitor for viburnum leaf beetle egg sites on the tips of susceptible host plant twigs at any time, but especially from the current season's July through May of the next year. They may be mainly found on the undersides of current year's growth, on young branches. Monitor for larvae from approximately late April until mid-June. Search leaf undersides when young larvae are present, and as the season progresses older larvae may be found on upper and lower leaf surfaces. Look for adult viburnum leaf beetles and signs of their feeding from late June until the first hard frost in the fall. The pupal life stage is the hardest to find and may not be useful for monitoring. Pupae are found in moist soils from mid-June until the adults emerge by the beginning of July.
Pruning out and destroying egg laying sites before the larvae emerge is a great way to locally (in a planting) reduce the population of this insect. Do so from early October to mid-April, when plants are leafless and seeing the egg laying locations may be easier. (It may be useful to wait until the winter/spring, as some managers have commented that destroying egg sites too early in the fall may lead to missed eggs if some female beetles are still alive and laying eggs.) Additionally, larvae have been found to crawl down the main stem of the shrub to the soil, where they pupate. It may, therefore, be helpful to wrap the base of an infested shrub with a barrier material and apply a sticky substance in an attempt to capture the larvae moving to the ground to pupate. Do not apply sticky substances to the bark of the shrub itself. If installing new plantings, only plant species of viburnum that are known to be the most resistant to this insect in Massachusetts.
Natural enemies of the viburnum leaf beetle have been observed. These include but are not limited to: lady beetle adults and larvae, lacewing larvae and spined soldier bug (Podisus maculiventris) nymphs (Brewer Fact Sheet, 2018). Biological control options for this insect are currently being researched. For example, quarantine studies of Eurasian egg parasitoids (Aprostocetus spp., Hymenoptera: Eulophidae) have been conducted, however due to lack of host specificity they were not recommended for use against the viburnum leaf beetle in North America (Gaylord, 2009). More information is likely to become available in the future.
Entomopathogenic nematodes were effective at managing viburnum leaf beetles in lab bioassays. Heterorhabditis bacteriophora and Steinernema carpocapsae were very effective at killing pupae in the lab, reducing adult emergence by 76–100% (Weston and Desurmont, 2008). Nematode applications made before pupation were more effective in that laboratory study than those made after pupation, with H. bacteriophora consistently (but not significantly) more effective than S. carpocapsae (Weston and Desurmont, 2008).
Acephate (larvae) (NL)
Azadirachtin (NL)
Chromobacterium subtsugae (NL)
Clothianidin (NL)
Cyantraniliprole (NL)
Dinotefuran (NL)
Flonicamid+cyclaniliprole (N)
Horticultural Oil (L)
Imidacloprid (L)
Permethrin (L)
Pyrethrin+sulfur (NL)
Spinetoram+sulfoxaflor (N)
Spinosad (NL)
Choose reduced risk insecticide options to preserve natural enemies and reduce the potential for impact on pollinator populations. Both insecticidal soap and spinosad have been found to be effective at managing viburnum leaf beetle larvae. Direct contact with the larvae is required for contact insecticides to be effective. Chemical management of young larvae (late April, early May) is most likely to be effective. Dormant horticultural oil applications (done before host plant leaves emerge) at high rates (4%) have been found to reduce egg hatch by 75-80% (Brewer and Weston Fact Sheet, 2018).
Active ingredients that may be applied systemically include: Clothianidin (soil drench), cyantraniliprole (injection, soil drench), dinotefuran (soil drench), and imidacloprid (soil drench).
Make insecticide applications after bloom to protect pollinators. Applications at times of the day and temperatures when pollinators are less likely to be active can also reduce the risk of impacting their populations.
Note: Beginning July 1, 2022, neonicotinoid insecticides are classified as state restricted use for use on tree and shrub insect pests in Massachusetts. For more information, visit the MA Department of Agricultural Resources Pesticide Program.
