Boxwood psyllid

About

A tiny sap-sucking insect common across the temperate US whose nymphs make young boxwood leaves cup upward in spring (UMass). The damage is mostly cosmetic and usually does not need spraying.

Spotting it

Damage

Nymphs feed on opening buds and new leaves, which cup upward like little spoons and may yellow. The cupped leaves can stay on for a few years, but plants usually push new leaves the same season (UMass).

How to find it early

As buds open in spring, look for cupped leaf tips with white, waxy threads inside. Shaking the shrub in June can flush out the tiny adults (UMass).

When

Spring (nymphs) into early summer (adults).

Life cycle

One generation a year. Females tuck orange eggs between bud scales in early summer; the young nymphs spend winter inside the eggs and come out as buds open in spring, feed inside the cupped leaves under white waxy fluff, and become small green winged adults by June (UMass).

What to do, gentlest first

Start at the top. Sprays are a last step; always read and follow the product label.

1. Tolerate it or plant less-favored boxwoods Prevent

   The damage is mostly cosmetic. American boxwood is hit hardest; English boxwood is less affected, and 'Green Mountain', 'Green Velvet', 'Glencoe' ('Chicagoland Green'), 'Fiorii' and 'Arborescens' are partly resistant (UMass).

2. Horticultural oil in spring Organic spray

   If cupping is not acceptable, an oil spray in spring before buds open targets the eggs with the nymphs inside; insecticidal soap works on nymphs if you spray as soon as they appear, before cupped leaves shelter them (UMass).

   Oil can harm bees it hits (PNW 591); spray after bloom and when bees are not flying (UMass). Follow the label.

Plants it goes after

Boxwood

Pressure by region

UMass calls it common in the temperate United States; ratings are estimates.

Ratings come from extension sources where available; some are estimates, as noted above.