Advice
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Viburnum beetle (Pyrrhalta viburni)
Attacks by viburnum beetle can result in severe defoliation of some Viburnum species.
Plants affected
Viburnum opulus (pictured right), V. tinus and V. lantana can suffer severe defoliation. Other viburnums are less affected or free of damage.
Symptoms
Holes are eaten in the leaves, with the larger leaf veins remaining, giving the foliage a lace-doily appearance. Creamy yellow larvae, with black markings and up to 8mm long, are present in April to early June. Greyish brown adult beetles, 4.5-6mm long, feed on the leaves from late July to September.
Biology
Most of the damage is caused by the larvae during late spring. When fully fed, the larvae pupate in the soil. Adult beetles emerge in late summer and deposit overwintering eggs in the woody stems. Adult feeding damage on the foliage is much less extensive than that of the larvae. This pest has become much more troublesome during the last 10 years.
Control
Inspect susceptible viburnums during the spring for signs of feeding on the new foliage. This will indicate when the overwintered eggs are hatching. If necessary, spray the plants with bifenthrin (Scotts Bug Clear Gun, Bayer Sprayday Greenfly Killer Plus or Doff All In One Garden Pest Killer) or thiacloprid (Provado Ultimate Bug Killer Ready To Use).