What attacks boxwood: pests and diseases the sources name
A register of the moth, the blight fungi, the psyllid and the leafminer that the Canadian Food Inspection Agency, the Royal Horticultural Society, the University of Maryland, Missouri Botanical Garden and Penn State Extension tie to boxwood (box): which plants each row names, where it is recorded, the status each source gives, and where the full profile is.
Checked against the sources at the bottom of this page on October 9, 2026. Rules, fees and pay change: the source has the last word.
This page reports what the named sources say. It is not a diagnosis of any plant and does not say what should be done with one. Boxwood is a shrub, not a tree. Each row names its source, all read on October 9, 2026. Where this site has a full profile, the row links it, and the regulated status table is on the linked page.
The register
| Agent | What the sources record |
|---|---|
| Box tree moth, Cydalima perspectalis. Full profile | Kind: Moth whose caterpillars eat the foliage Hosts: The Canadian Food Inspection Agency says that in Canada it is found exclusively on boxwood shrubs. The Royal Horticultural Society says box tree caterpillars can completely defoliate box plants. Where and status: The Canadian agency says it is a regulated pest in Canada and names the regulated areas, which are listed on the box tree moth profile. The Royal Horticultural Society reports a wide spread in England, mainly London and the areas around it, and arrival in the rest of the United Kingdom and in Ireland. |
| Box blight or boxwood blight, Calonectria pseudonaviculata (also C. henricotiae) | Kind: Fungus of leaves and stems Hosts: The Royal Horticultural Society says it largely affects box (Buxus) in the United Kingdom, with other plants of the box family also susceptible, and that two closely related fungi cause it. Missouri Botanical Garden lists boxwood, pachysandra and sweet box as hosts. It says repeated defoliation can kill young plants and that defoliation of larger plants makes them susceptible to infection by other pathogens. Where and status: The University of Maryland says it has caused defoliation of boxwoods across Europe since the late 1990s, was found in North Carolina and Connecticut in October 2011, and has since turned up in several northeastern states, in Oregon and in British Columbia. Missouri Botanical Garden gives the first confirmed United States occurrence as 2011 and lists Missouri and Illinois among states where it was later found. No regulated status is given on the pages read. Signs as listed: The University of Maryland names numerous narrow black cankers on the green stems as the key symptom that separates it from Volutella blight and Macrophoma leaf spot, with leaf spots, browning and leaf drop starting low in the canopy. The Royal Horticultural Society describes bare patches, brown leaves and dieback, most active in wet periods, and white spore masses under leaves in wet conditions. It says the fungus can survive on fallen leaves for up to 6 years. |
| Volutella blight | Kind: Fungal disease Hosts: The Royal Horticultural Society calls it a second blight that also affects box and is less serious than box blight, and says its spore masses look pink where box blight spore masses are white. The University of Maryland shows straw-coloured leaves from it. Where and status: No distribution or status given on the pages read. |
| Boxwood psyllid, Cacopsylla busi, and boxwood leafminer, Monarthropalpus flavus. Full profile | Kind: Sap-feeding insect and leaf-mining fly Hosts: Penn State Extension says psyllid nymphs feed on expanding foliage and cup the leaves, with several nymphs sometimes enclosed in one pocket, and that the leafminer larva feeds between the upper and lower leaf surfaces and causes blisters, with infested leaflets often dropping early. Where and status: No regulated status is given on the Penn State pages. The linked profile has the other sources. |
How the sources describe the effects
The University of Maryland says boxwood blight leaves the roots alone, so bigger plants can put out new leaves in the growing season yet lose their ornamental value as leaf loss worsens, and that repeated defoliation and dieback from stem cankers have killed small rooted cuttings in nursery propagation. Penn State Extension calls the cupping from the psyllid very noticeable and says the leafminer can cause extensive damage to foliage, leaving ragged plants with occasional dead twigs. The Royal Horticultural Society warns that the dieback from box tree caterpillar feeding is not to be confused with the dieback of box blight.
Who the sources say to report to
The Canadian Food Inspection Agency asks that box tree moth or signs of it on boxwood in Manitoba, Saskatchewan, Alberta or British Columbia be reported immediately. The pages read for the blights, the psyllid and the leafminer name no report line. The offices for each country are on the report a pest in Canada and report a pest in the United Kingdom pages.
Sources
- Canadian Food Inspection Agency, box tree moth page, read October 9, 2026
- Royal Horticultural Society, box tree caterpillar advice page, read October 9, 2026
- Royal Horticultural Society, box blight advice page, read October 9, 2026
- University of Maryland Extension, boxwood blight (updated February 22, 2023), read October 9, 2026
- Missouri Botanical Garden, boxwood blight page, read October 9, 2026
- Penn State Extension, boxwood psyllid, read October 9, 2026
- Penn State Extension, boxwood leafminer, read October 9, 2026