Viburnum Under Siege. Part Two

Editor’s note: this is part two of this series. Don’t miss part one of Viburnum Under Siege.

The accidentally introduced pest, viburnum leaf beetle (Pyrrhalta viburni) or VLB for short, can destroy a shrub in just a couple of years. Unfortunately it continues to spread through North America. So I am trying to learn more about it, hoping that we can protect the viburnums in our area. This is the information that I have gathered from the sites listed and from my own observations. It doesn’t look very encouraging.

VLB larvae and leaf damage

© Beatriz Moisset

The grubs or larvae emerge from eggs early in the spring. They are yellowish or greenish, with black markings and can reach one third or a quarter of an inch in length.

They spend a few weeks feeding on the leaves by making numerous little holes between the veins. These holes are easy to identify. By early or mid June they climb down along the stems and bury themselves in the ground to pupate. When I searched for them in mid June, I found none, only the damage remained.

Viburnum Under Siege

Leaf damage inflicted on arrowwood

by the viburnum leaf beetle

© Beatriz Moisset

 The shoots of Viburnum dentatum are thin, strong and straight. Native Americans used them for arrow shafts. That is why this shrub is often called arrowwood. Until recently it was considered as a plant free from serious pests. Now, the arrowwoods in my area are under attack by an invasive leaf beetle.

Last May (2010), I began noticing leaves full of holes (skeletonized); something that I have never seen before. I finally spotted the culprits, little bugs hiding on the underside of damaged leaves. They look somewhat like caterpillars, but not quite; they are greenish, with black dots. A visit to the Bugguide site helped me identify them and provided links to several university sites full of information (see below). They are the larvae of the viburnum leaf beetle (VLB for short, Pyrrhalta viburni), an introduced pest from The Old World. Both the larvae and adults of this beetle feed exclusively on a variety of species of viburnum.

Viburnum leaf beetle larva and leaf damage

© Beatriz Moisset