Boxwood Psyllid

Garden Clippings for June 13, 2026

Most home landscapes have at least a few Boxwood plants. We love Boxwood for their dense evergreen foliage, their slow growth, and versatility. Boxwood are hardy, will grow in sun or shade and will tolerate both wet and dry soil.

Until recently, Boxwood was considered a relatively pest and disease-free plant. However, in late 2024, Box Tree Moth arrived in Lambton County, and by the following spring it had begun causing serious damage by feeding on Boxwood foliage, sometimes leaving only a skeleton of twigs behind. Damage was most noticeable in Camlachie and Forest, but it is expected to spread more widely over the next few years.

Box Tree Moth can be controlled by spraying with BTK (Bacillus thuringiensis kurstaki), a naturally-occurring biological insecticide that will effectively keep the insects at bay. Spray as soon as infestation appears in late spring, and again in early September when the second cycle begins. Apply once a week while caterpillars are feeding. If damage is not severe, handpicking may provide adequate control.

Symptoms of Box Tree Moth are easy to detect, but often after damage is severe. Leaves are eaten, and fine webbing will be present on leaves and branches. The clever caterpillar is green with black stripes and spots, blending with Boxwood plants. The adult moth is dirty white with a brown border.

If Box Tree Moth is not destructive enough, inspect your garden for Boxwood psyllids, pronounced “sillid”. Since late May, I have seen hundreds of Boxwood plants, with infestations ranging from minor to severe.

Boxwood psyllid is detected in two ways: by cupping or curling of leaves or by the presence of tiny white waxy spots that look like twisted grains of rice. Damage is primarily cosmetic, rarely causing serious setbacks. Growth can appear stunted and plants can appear to lose their vigor.

The life cycle of Boxwood psyllid begins when the adult, a small green insect with translucent wings, lays eggs on Boxwood plants in mid to late summer. Eggs hatch in spring and become tiny nymphs. The nymphs recreate themselves 5 times until becoming adults that soon lay eggs again. There is one generation or cycle per year.

To control Boxwood psyllid, consider starting with a blast of water on affected plants. A corn broom will also dislodge many psyllids. Pruning the plants, followed by discarding the leaves along with insects will also provide some control.

Spraying Boxwood with horticultural oil or insecticidal soap in spring will kill the young nymphs before becoming adults. Both are safe products made from natural sources. When spraying, target the Boxwood so adjacent beneficial insects are not affected.

If your Boxwood has been affected by Box Tree Moth or psyllids, part of the plants’ recovery will include water and fertilizer. Use a granular plant food to promote renewed growth that will strengthen the plant and improve its health.