Viburnum Leaf Beetle
Pyrrhalta viburni
A yellowish-brown beetle whose larvae and adults both feed only on viburnums, skeletonizing the leaves in spring and chewing holes in summer. Repeated defoliation over a few years can weaken and kill a shrub.
🔎 How to spot it
Adults are about a quarter inch long and yellowish brown. Larvae grow up to a third of an inch and range from yellowish green to light brown, marked with rows of black spots and dashes. Look for rows of small, dark, cap-covered egg-laying pits on the undersides of young twigs.
🥀 Damage it causes
Spring larvae chew the leaf tissue between the veins, leaving a lacy, skeletonized pattern, and summer adults chew oblong holes. Heavy infestations can completely strip a shrub, and repeated defoliation weakens the plant and can eventually kill it. Arrowwood and the cranberrybush viburnums are the most susceptible.
🛡️ Prevent it
Choose less-susceptible viburnums such as doublefile, Koreanspice, and Judd viburnum when planting. Between October and spring, inspect young twigs for the rows of egg pits and prune out and destroy infested twigs before eggs hatch. Encourage lady beetles, lacewings, and other predators that feed on the larvae.
🧯 If it is already here
Apply horticultural oil to egg-laden twigs before bud break to reduce hatch. Target small larvae in spring with insecticidal soap, spinosad, neem, or horticultural oil before they cause major damage. Conventional contact insecticides and systemic soil drenches applied after bloom are options for severe cases.
💡 Good to know
There is one generation a year, and the beetle overwinters as eggs in the twigs, which is why dormant-season pruning of egg-laid twigs is so effective. Each female can lay up to about five hundred eggs in capped pits. Doublefile viburnum is among the kinds it attacks least.
🌱 Plants it attacks
2 plants in the library can be attacked by this pest
For educational and informational purposes only. Pest control advice is general guidance drawn from university cooperative extension sources; always identify a pest positively and read and follow the label on any product before use, especially around food crops, children, and pets.