Viburnum leaf beetle (Pyrrhalta viburni), a pest of Viburnum species including arrowwood and European cranberry bush, has been confirmed in three new counties in Massachusetts.
The Viburnum leaf beetle was first discovered in Massachusetts in 2004, in Berkshire County. In July 2008, new sightings of this introduced pest were reported in Bristol, Franklin, and Middlesex County, and were recently confirmed by Robert Childs, an entomologist at UMass Extension. Eradication efforts at these sites are currently underway.
Viburnum leaf beetle attacks only viburnum plants. The most susceptible species are arrowwood viburnums (V. dentatum complex), European and American cranberry bush (V. opulus, including var. americana), Possum-haw (V. nudum), Rafinesque viburnum (V. rafinesquianum), and Chinese or Taiwanese viburnum (V. propinquum). Many other species are also known to be susceptible, including: Black haw (V. prunifolium), Mapleleaf viburnum (V. acerifolium), Nannyberry (V. lentago), Sargent viburnum (V. sargentii), Wayfaringtree (V. lantana), and Wright viburnum (V. wrightii).
In late summer and fall it is the adult stage of the Viburnum leaf beetle that is active. Adult feeding damage can be seen on viburnum leaves as irregular circular to elliptical holes. The beetles are approximately 5mm long (less than ¼ of an inch) and are brown, with dark markings on and behind the head. Adults feed from July through the fall, until leaf drop occurs, and will be laying eggs for the remainder of the growing season. Egg-laying sites are small, brownish-black bumps, about 1-2mm in diameter, that can be found in rows along the terminal twigs of the plant.
With the distribution of this beetle continuing to expand throughout the state, ornamental plantings and nursery stock as well as native Viburnums could be at risk. It is important to learn to recognize the symptoms of Viburnum leaf beetle damage so that infestations can be detected and dealt with as early as possible. Heavy infestations by Viburnum leaf beetle can defoliate shrubs, cause dieback, and eventually kill plants. Shrubs repeatedly defoliated over a period of two to three years are likely to die.
If you think you have seen the Viburnum leaf beetle, please let us know using our reporting form.
Resources for additional information:
This pest alert is from the Massachusetts Introduced Pests Outreach Project, a collaboration between the Massachusetts Department of Agricultural Resources and the UMass Extension Agriculture and Landscape Program, aimed at preventing the establishment of new pathogens and pests in Massachusetts. To get alerts by email, visit http://massnrc.org/pests/signup.aspx.