Viburnum Leaf Beetle Alert

The viburnum leaf beetle, Pyrrhalta viburni, has now been seen in Massachusetts and Connecticut, after spreading through Maine, New Hampshire, Vermont, upstate New York and northern Pennsylvania since 1996. Native to Europe, this chewing beetle is especially fond of our native viburnums, causing their death after several years of defoliation.

Gardeners can be instrumental in deterring the spread of these voracious beetles. The tiny larvae emerge in late April and begin chewing on the underside of new leaves, dropping to the ground in June to pupate in the soil. In July, they emerge as adult beetles and continue eating until frost, often defoliating entire plants. You may not see these tiny 1/2” beetles until you notice the damage. The female beetles lay about 8 eggs in each of the many cavities they dig along young shoots, sealing each cavity with chewed bark and excrement. Look for rows of small rough bumps along these shoots and clip off any affected branch, disposing of it in the trash. This should be done before the larvae emerge in April.

The most susceptible species are American cranberry bush viburnum, Viburnum opulus var. americanum, formerly V. trilobum, Arrowwood viburnum, V. dentatum, Chinese viburnum, V. propinquum, Downy arrowwood viburnum, V. rafinesquianum, European cranberrybush viburnum, V. opulus, Smooth witherod viburnum, V. nudum, and Fragrant viburnum, V. farreri ‘Nanum’.

The most resistant species are David viburnum, V. davidii, Dawn viburnum, V. x bodnantense, Doublefile viburnum, V. plicatum f. tomentosum, Judd viburnum, V. x juddi, Koreanspice viburnum, V. carlesii, leatherleaf viburnum, V. rhytidophyllum, Siebold viburnum, V. sieboldii, and Tea viburnum, V. setigerum. Other species fall into the moderately susceptible and susceptible range. Because of the devastation this beetle can cause, it would be prudent to examine all your viburnums and add only the most resistant species to your garden.

For more information, see Fine Gardening, December 2005 or search for Viburnum leaf beetle on the Internet. Cornell University is tracking the spread of the beetle and the species at greatest risk. Report any findings to their web site: www.hort.cornell.edu/VLB.

Louise Weber, Conservation/Preservation Chairman

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