Viburnum Leaf Beetle

Viburnum Leaf Beetle, Pyrrhalta viburni (Paykull), is an invasive, non-native beetle that first appeared in New York along Lake Ontario in 1996, and has steadily spread. It is a voracious eater that can defoliate viburnum shrubs entirely. Plants may die after two or three years of heavy infestation.

The viburnum leaf beetle is approximately 4.5 to 6.5 mm in length. The head, thorax and elytra are generally brown, and the anterior edge of the elytra is slightly dark. The dorsal surface is covered with dense golden-grey hair . In overall appearance, viburnum leaf beetle resembles the elm leaf beetle except for minor differences in size and color. Generally, the elm leaf beetle is slightly larger with a body length of 5.8 to 6.8 mm . In addition, the elm leaf beetle has a light brown body with a dark stripe on the edge of each forewing, almost reaching the apex tip of wing.

Viburnum leaf beetle adults and larvae consume native and exotic species of viburnum in natural and managed landscapes. Although they show a preference for species with little hair (pubescence) on the foliage, they severely damage many of the approximately 150 known species of viburnum. Viburnum leaf beetle commonly grown viburnums into highly susceptible (first to be attacked; generally destroyed within 3 years), susceptible (eventually destroyed), moderately susceptible (usually not destroyed) and resistant species (little or no feeding damage). Most species in all groups suffer more feeding damage when grown in the shade.

Life Cycle : Adult females lay eggs from late June to October or until the first killing frost. During a females life span, she lays up to 500 eggs on viburnum twigs and small branches by excavating deep, rounded pinhead sized egg cavities in a straight row on the under surface of the terminal twigs.

After filling the egg cavity with five to eight eggs, the female closes the opening with a lid or “cap” made of excrement and chewed bark held together by a mucous secretion that hardens upon exposure. The cap not only protects the egg from predation, but also absorbs water to maintain the humidity.

Viburnum leaf beetle overwinters as EGGS, and requires a chilling period of approximately five months. Eggs hatch around May when leaf buds open. Larvae pass through three developmental stages attaining a length of 10 to 11mm (2/5”) at maturity. Larval development is fast in the temperature range 63-72°F and levels off at 81°F.

The development period from egg hatch to adult emergence lasts eight to ten weeks. The matured larvae enter the soil to pupate from early to mid-June and emerge as adults in July. The pupal stage lasts for about 10 days.

Damage : Viburnum leaf beetles feed on many species of Viburnum in both adult and larval stages. The beetles are very damaging because of this successive feeding by larvae followed by adults; bushes do not have time to re-vegetate between beetle stages. Two or three consecutive years of defoliation can cause significant die-back of the canopy and kill a bush.

The beetles appear to prefer some species and cultivars over others. New York State entomologists are developing a host preference list. Viburnum dentatum (arrowwood viburnums), V. opulus (European cranberrybush), V. opulus var. americana (American cranberrybush), V. rafinesquianum (Rafinesque Viburnum) and V. sargentii (Sargent Viburnum) are the most susceptible to infestations.

The Viburnum leaf beetle may not only be a pest problem for gardeners and landscapers but may also cause problems for nurseries, growers, restoration programs and natural habitats.

Management: Begin monitoring for eggs after the first frost in fall and winter. Prune out or otherwise physically destroy the eggs. Begin monitoring for larvae when the first leaves begin to form in the spring. Pick off the small larvae as you find them. Continue to physically remove larvae when you regularly inspect bushes. While this management hasn’t been tested, NY entomologists suggest applying a sticky barrier such as Tanglefoot® to the base of the bush stems. They found that the larvae do not drop directly to the soil to pupate but crawl down the stem. The application of Tanglefoot® will be identical to the methods you would use for foiling adult rootweevils. After the adults have emerged, regularly remove and destroy the adults. It is best to remove them in the morning before they become too active

If you plan on planting Viburnum plants into your landscape, consider using a species or cultivar that shows some resistance. Known resistant species include V. plicatum var. tomentosum (doublefile viburnum), V. carlesii (Koreanspice viburnum), V. burkwoodii (Burkwood viburnum), V. × juddii (Judd viburnum), V. × rhytidiophylloides (lantanaphyllum viburnum), and V. rhytidiophyllum (leatherleaf viburnum).There are no known natural enemies that are specific to Viburnum leaf beetle.

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