What's eating my blackhaw viburnum?

Blackhaw Viburnum is most seriously affected by viburnum leaf beetle, which can completely defoliate the shrub. Aphids — especially the snowball aphid — cluster on new growth in spring. Deer browse stems and foliage readily. The plant's dense structure also makes it attractive to scale insects on older wood.

Larvae skeletonise leaves from mid-spring, leaving only the main veins; adults continue feeding in summer, and repeated defoliation over two to three years can kill the shrub. Inspect stems for overwintering egg-capped pits in autumn and crush or prune them out. Spray larvae with insecticidal soap, pyrethrum, or spinosad in mid-spring. Prune heavily infested branches.

Tightly clustered colonies on new shoot tips in spring cause leaf curl, distortion, and sticky honeydew. Blast off with a strong water jet. Apply insecticidal soap or neem oil if colonies persist into summer. Natural predators (ladybirds, lacewings) normally suppress populations.

Stems and foliage browsed, particularly in winter; bark rubbed by bucks in autumn, causing stem damage. Install individual tree guards or deer fencing. Apply deer-repellent spray and reapply monthly through dormant season.

Oyster-shaped grey-brown shells on older bark; severe infestations cause branch dieback and reduced vigour. Apply dormant horticultural oil in late winter before bud break. Remove heavily encrusted branches. Treat crawlers in early summer with insecticidal soap.