While the leaves of viburnum (Viburnum spp.) shrubs have fallen, if the viburnum leaf beetle (Pyrrhalta viburni) was present earlier this year, the eggs laid on the shrubs newest growth will be evident. This non-native invasive species feeds as both a larvae and adult, skeletonizing the viburnum leaves. When population levels of the insect increases, defoliation of the shrub becomes more obvious. The insect will feed on naturally growing viburnums, as well as those planted in landscapes, in commercial plantings and at gardens and arboretums.
This non-native insect was first detected in Ohio in the northeast corner of the state, and has been moving west and south from this first buckeye find. The insect does spread naturally, but can also be moved on plant material. Sometimes infestations pop-up in front of the leading edge of the infestation when infested plants are planted in an uninfested area.
While this insect feeds exclusively on viburnums, some seem to be more favored than others. Below are a list of some of this insect's favorites.
- Arrowwood viburnum (V. dentatum)
- European cranberrybush viburnum (V. opulus)
- American cranberrybush viburnum (V. opulus var. americanum = V. trilobum)
- Rafinesque viburnum (V. rafinesquianum)
If you noticed VLB activity earlier this year, it is a great time to revisit the infested shrubs, looking for egg laying sites on the newest growth. Even if you didn't observe VLB activity, scouting for eggs is a simple diagnostic step that everyone can do.
The eggs are laid on the branches, often near the tips, or on the newest growth. Eggs are typically laid in a row on the undersurface of the twigs. A female can lay up to 500 eggs.
If these egg laying sites are found, an effective means of mechanical control is to prune and destroy infested twigs. The pruned twigs should be buried, burned, placed into an active composting pile, or bagged and placed in the garbage.
For additional information about VLB, check out this OSU FactSheet written by Curtis Young at: https://ohioline.osu.edu/factsheet/anr-39#:~:text=Adults%20appear%20in%20mid%2Dsummer,first%20heavy%20(killing)%20frost.&text=Figure%206%3A%20Adult%20viburnum%20leaf,Young%2C%20Ohio%20State%20University%20Extension.
If you happen to encounter VLB, we ask you report your finding on the Great Lakes Early Detection Network (GLEDN) App. For more information about the GLEDN App, check out the website at: https://apps.bugwood.org/apps/gledn/ Additionally, the OSU Woodland Stewards Program has a recorded presentation on how to use GLEDN at: https://osu.zoom.us/rec/play/uJIoJeGt_DM3EteV5QSDBaR_W47oJq2s23AZ-qALzUrjWyMLNVegZLZHN7dWBA7rrJjYTg1YTuwjBfRF or a quick video link at: https://mediasite.osu.edu/Mediasite/Play/d9d998f0840042c39f1f84bbd68a5b061d