Plane lace bug: a new arrival in London’s treescape
Christopher Berman, Forest Research Entomologist
Figure 1: Nymph and adult plane lace bug. (Crown copyright/Fera Science/David Crossley)
Figure 2: Underside of leaf covered in plane lace bug adults, nymphs and frass droplets (left). Top of leaf with stippling damage (right).
Having travelled across continents over recent decades, the plane lace bug (Corythucha ciliata) has now established itself in London, adding a new chapter to the story of the capital’s treescape.
Despite the insects’ fragile and delicate appearance, they are resilient, mobile, well adapted to urban life – and remarkably robust. This minute species lives quietly on the undersides of plane leaves and is easy to overlook. Adults have finely patterned, lace-like wings that give them a surprisingly intricate appearance, while the darker, spiny nymphs (the immature, wingless stage of the insect) provide a striking contrast beneath the foliage.
Lace bug lifestyle
Plane lace bugs feed on sap from foliage. Both lace-covered adults and the dark nymphs use fine, needle-like mouthparts to pierce the leaf surface and draw out the nutrient-rich fluids.
This feeding drains sap from the leaf cells, causing them to die, creating pale stippling (i.e. tiny dots) on the upper leaf surface. As feeding accumulates, those speckles can merge into bronzed patches and, in heavier cases, contribute to early leaf fall.
Activity builds through the season because the lace bug can produce overlapping generations. Nymphs hatch as small, dark, spiny insects and progress through several stages, feeding continuously as they develop. Warmer conditions speed up this process, so damage is often most visible in mid to late summer.
The nymphs and adults often cluster around the leaf veins, living their lives and producing plenty of excrement in the form of dark, tar-like frass droplets, which can be clearly seen on heavily infested leaves (Fig. 2).
Once the adults have had their fill and it starts getting colder in autumn, they move underneath loose bark or into sheltered crevices to overwinter. After hiding away from the cold, the next spring they become active again and begin laying eggs on the undersides of plane leaves.
The adults can fly, but only short distances. Their spread is just as likely to be passive, with insects blown on the wind to neighbouring trees, or carried on clothing and equipment. Over longer distances, movement of people, vehicles and plant material is the main route of dispersal.
Symptoms to look for
Upper leaf surface:
- fine, pale stippling
- bronzing or browning in late summer
- early or uneven leaf drop
Leaf underside:
- clusters of adults and spiny black nymphs
- dark, tar-like frass droplets
- cast nymph skins
Travel history: origins and expansion
Native to North America, the plane lace bug’s globe-trotting journey began in the mid-20th century. It established in northern Italy in 1964 and spread widely across Europe during the following decades, eventually appearing in Asia and Australia. Its reliance predominantly on plane species, including London plane (Platanus × hispanica), oriental plane (P. orientalis) and American sycamore (P. occidentalis), has made it a successful urban specialist.
The UK first encountered this insect in 2006, when it was discovered on imported plane saplings at a Bedfordshire nursery. Swift treatment prevented establishment, and no signs were seen in the following years. For nearly two decades, the species seemed absent from Britain. That changed in summer 2024. An adult plane lace bug was spotted on the strap of a commuter’s backpack in Kensington, an unexpected discovery that quickly proved significant. The sighting was posted to iNaturalist (a free citizen science app and online social network that helps users identify plants, animals and insects using image recognition), prompting rapid surveying by Forest Research, the Forestry Commission and the Animal and Plant Health Agency (APHA).
Following this discovery, more than 1,600 plane trees across central London were examined. Symptoms were recorded across multiple areas, from subtle stippling up to heavy bronzing, confirming that the species had fully established. On several heavily infested trees, adults were found sheltering beneath bark flakes, readying for winter. Their successful overwintering was confirmed in spring 2025.
This recent introduction appears unrelated to the isolated nursery incident of 2006. Instead, the pattern strongly suggests hitchhiking insects carried into London on luggage, vehicles or imported materials. Once here, they found a city filled with ideal hosts and a climate suited to rapid population growth.
Management and monitoring
In most cases, plane lace bugs are a visual concern rather than a functional one.
However, in parts of Europe, large insect populations mean lace bugs sometimes fall from canopies onto people below and if they are unwittingly provoked or disturbed, their defensive bites can cause mild skin irritation. These incidents are extremely rare, and less painful than bee or wasp stings, but demonstrate how higher numbers of plane lace bug can affect city inhabitants more directly.
London’s plane trees are mature, tall and widely distributed across public spaces, this means chemical control is not considered appropriate or necessary. Treatments would be difficult to apply effectively, costly and short lived. Instead, management focuses on:
- monitoring symptoms across the city
- educating arborists and the public
- encouraging reporting through
- TreeAlert, an online, citizen-science reporting tool for Great Britain, managed by Forest Research, that enables both professionals and the public to report suspected tree pests and diseases
- documenting early indicators of change
London plane is a remarkably resilient species and can tolerate substantial feeding damage without long-term decline. While plane lace bug alone is not usually considered a major driver of tree decline, multiple years of heavy infestation can weaken plane trees and make them more susceptible to secondary infections. In severe cases, and especially when compounded by other stresses like drought, this could contribute to tree decline or death.
In most cases, the plane lace bug’s presence is best managed through building awareness, rather than intervention.
Another emerging threat: oak lace bug
Another, closely related, North American species, the oak lace bug (Corythucha arcuata), has become problematic in several European countries. It causes extensive leaf browning and can exacerbate drought stress in oaks. Although not currently present in the UK, it has quickly spread throughout the continent, highlighting how quickly lace bugs can establish and expand when conditions are suitable.
The arrival of plane lace bug in London underscores the need for continued vigilance for similar pests which can establish in urban environments.
The role of arborists and the public
Urban areas are uniquely positioned for early pest detection. With thousands of trees and many people passing beneath their canopies each day, symptoms are more likely to be noticed early.
Arborists can play a critical role by:
- including lace bug checks in routine inspections of plane trees
- capturing clear photographs of symptoms and insects
- reporting any suspect findings promptly to TreeAlert
- helping to raise awareness among clients and the public
Members of the public, too, can support early detection by learning what to look for and reporting unusual findings. The Forestry Commission and Defra have produced an information leaflet and video which are available online as a reminder of the key signs to look for (see below for more details).
A changing urban ecosystem
The arrival of plane lace bug in London illustrates how dynamic city ecosystems have become. As global travel continues and the climate warms, more species will find opportunities to establish themselves in new places, often unnoticed at first.
So, next time you find yourself under a London plane, pause for a closer look. You may spot the delicate patterning on a tiny leaf dweller which belongs to one of the city’s newest arrivals, quietly illustrating how nature continues to travel alongside us.
Further information
www.forestresearch.gov.uk: and search for ‘plane lace bug’
What is the Plane lace bug? Video – youtu.be/aTZqBBxd51A?si=XHMrvwTMp0Fddv5Z
TreeAlert – www.forestresearch.gov.uk/tools-and-resources/fthr/tree-alert/
Why is London so welcoming?
- Plenty of plane trees: London plane is one of the city’s most iconic species, lining streets, boulevards, parks and public squares. Its abundance provides a continuous network of suitable host trees through which lace bugs can spread.
- The urban heat island effect: London’s warm microclimate extends the growing season and increases overwinter survival, which in turn benefits this insect, allowing it to produce multiple generations each year.
- A city of global movement: Millions of people and tonnes of goods pass through London each week. With that flow comes the heightened risk of small insects travelling unnoticed and establishing in new locations.
This article was taken from Issue 213 Summer 2026 of the ARB Magazine, which is available to view free to members by simply logging in to the website and viewing your profile area.