Pyrrhalta viburni is a species of leaf beetle native to Europe and Asia, commonly known as the viburnum leaf beetle. It was first detected in the United States in Maine in 1994. In England the Royal Horticulture Society has named Pyrrhalta viburni as the country’s “number one pest species”. 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, VLB 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.
viburnum leaf beetle a pest that has the potential to become a serious problem in nurseries and landscapes in Pennsylvania. Adults and larvae feed on plants belonging to the genus Viburnum, sometimes causing their death. This species is native to Europe, but it has been detected in Canada and more recently, in western and central New York and Maine. The viburnum leaf beetle was first detected in Erie County in 2001 in northwestern Pennsylvania. During 2008 it was found in Bradford, Centre, Clinton, Crawford, Elk, Forest, Jefferson, Luzerne, Lycoming, McKean, Mercer, Monroe, Montour, Pike, Potter, Sullivan, Susquehanna, Tioga, Venango, Warren, and Wayne Counties. Recently, this species was also identified from Indiana and Butler counties in Pennsylvania. This species is closely related to the elm leaf beetle.
This pest feeds on viburnum and seems to prefer viburnums with little hair (pubescence) on the foliage that includes Viburnum opulus, EuroV. dentatum, arrowwood viburnum, and V. trilobum , American cranberrybush viburnum. This pest will also feed on V. lantana , wayferingtree viburnum, V. rafinesquianum , Rafinisque viburnum,V. acerifolium , mapleleaf viburnum, V. lentago , nannyberry viburnum, and V. sargentii , Sargent viburnum. Thus, many of the viburnums affected are species native to the United States.
Both larvae and adults feed on foliage between the midrib and larger veins. Feeding usually takes place on the lower leaf surface. Larvae can skeletonize young leaves by June. This is the first sign of an infestation. Emerging adults continue feeding on viburnum. Plants that have been defoliated for two or three consecutive years may die.
Let us take a look at how these beetles are causing damage in western Pennsylvania:
Viburnum leaf beetles have made way to Pa., but you can limit damage
By Jessica walliser ; Friday, July 3, 2015, 6:26 p.m.; Updated 8 hours ago
The viburnum leaf beetle (Pyrrhalta viburni) is a relatively new pest to Western Pennsylvania. Now found in parts of eastern Canada and several states in the Northeastern United States, this little beetle was accidentally introduced to North America from Europe in the 1940s. It was first noted in Pennsylvania in 2001. Gardeners have been reporting its presence in our part of the state for the past few years.
The viburnum leaf beetle targets only viburnums, with some species being more susceptible than others. This pest will not feed on any other species of plants. Heavy infestations can completely defoliate shrubs and cause significant dieback.
Adult beetles are about a quarter-inch long, with the females being slightly larger than the males. They are brown with darker markings along their sides. The antennae are almost as long as their bodies. Adult beetles can only be seen from early July through October, when females are actively chewing holes in small branches to insert their eggs. These egg-laying sites are often lined up in a straight row on the underside of a young twig.
The eggs overwinter on the plant, and by early May, they hatch. The resulting larvae are 1⁄2-inch long, wormlike, creamy-yellow grubs with dark markings. They’re found on the leaf undersides where they dine on the foliage. They can quickly skeletonize the tender, new growth, leaving only the leaf veins intact.
By early to mid-June, the larvae are finished feeding. They climb down to the ground to pupate. In early July, the adults emerge from pupation and go on to lay more eggs. There’s only one generation per year, but that single generation is capable of causing a whole lot of damage.
Viburnum leaf beetles are particularly fond of several species of viburnum, including arrow wood viburnums, American cranberry bush viburnums, black haw viburnums and European cranberry bush viburnums.
However, there are also several species of viburnum that seem to be fairly resistant to the beetles. These include Korean spice viburnums, Burk wood viburnums, and leather leaf viburnums.
Though viburnum leaf beetles are new kids on the block, there are some ways you can keep them from damaging your viburnums. First, plant only resistant species. Second, prune and destroy any infested twigs after the egg-laying period ends in the fall. Simply lift the twigs up to inspect their undersides. This is best done after the leaves have fallen off. Prune off any twigs with evidence of the characteristic lined-up egg-laying sites (they’ll appear as little bumps of sawdust-like material in a straight row).
Many predatory insects feed on viburnum leaf-beetle larvae, including ladybugs, lacewing larvae, soldier beetles, predatory stinkbugs, and ground beetles. Encourage these insects by planting lots of flowering herbs and annuals in your landscape.
Organic pesticides are also effective against the feeding larvae, especially when used as soon as damage is noted. Spinosad-based products (such as Captain Jack’s Dead Bug Brew) are useful, as is insecticidal soap. Be sure to spray both upper and lower leaf surfaces.
Pesticides used to control this viburnum pest, several (including organic pyrethrins) are contact poisons that also kill the beneficial insects. What makes this pest such a problem is that it feeds rapidly, and can defoliate a shrub (eat all the leaves) in a few days, leading to the death of the plant if this happens for two or three consecutive years. This pest has a fairly simple life cycle, beginning with larvae hatching from eggs in spring. These feed on leaves, then in early summer crawl down the stems to pupate in the soil. The adults emerge in midsummer, feed again on leaves, mate, and lay eggs which overwinter until next spring. Luckily, not all viburnums are created equal when it comes to feeding preference of this pest. Species that are most resistant to this pest still may become partially infested yet usually have little or no feeding. The most resistant species you should consider for landscapes if this pest is in your area include the Koreanspice, Judd, double file , leather leaf tea, and Siebold viburnums.
The most susceptible species you should avoid planting or consider replacing if this pest is nearby included arrowwood (dentatum), possum-haw (nudum), and cranberrybush (opulus) viburnums. Still susceptible, yet not as much so, are the mapleleaf (acerifolium), wayfaringtree (lantana), Sargent (sargentii), and Wright (wrightii) viburnums. Many of the other species you may find are likely moderately susceptible.
If planting resistant species or replacing susceptible ones isn’t an option, consider least-toxic control options before reaching for an insecticide. There are several beneficial insects that feed on viburnum leaf beetle larvae, including lady beetle larvae and adults, lacewing larvae, and spined soldier bug nymphs. Adults of both the lady beetle and spined soldier bug also eat viburnum leaf beetle adults. Thus one needs to b very careful in taking measures against these pests. We need a solution that helps protect our shrubs and plants from damage, while at the same time does not harm the environment or other beneficial insects in any way. So, how do we fight this pest?
At C Tech Corporation, we offer a safe and effective solution to deal with these insects. Termirepel™ is a non-toxic, non-hazardous product that primarily repels insects from the application. It is a broad spectrum repellent which works against almost 500 species of pestering bugs thus efficaciously repulse them away from the application. The best feature of this product is that it is environmentally safe and causes no harm to the insect as well as humans and the environment. It is available in masterbatch and lacquer form and as a liquid solution. To keep these insects at bay, this product can be coated in lacquer form or added in mulches or films. The repelling mechanism of the product would keep off the viburnum leaf beetle and any other insect that could harm our shrubs and plants.