Invasive tree of heaven is helping spotted lanternflies spread across US by feeding them its toxic sap; here’s why scientists are using it as a trap

An invasive tree that has spread across large parts of the United States is playing an unexpected role in the expansion of another invasive species. The tree of heaven, scientifically known as Ailanthus altissima, is one of the preferred hosts of the spotted lanternfly, allowing the destructive insect to find a readily available source of plant sap.

But the relationship between the two invaders has also given scientists and land managers a potential advantage. By understanding why spotted lanternflies are attracted to tree of heaven, researchers can use selected trees as traps while working to remove the invasive plant from the wider landscape.

What makes tree of heaven so invasive?

Tree of heaven was introduced to the Philadelphia region from Asia in the late 18th century and has since established itself across much of the US. It grows rapidly and can survive in disturbed environments, including roadsides, vacant lots, railway corridors and other areas where native vegetation may struggle.


The tree is particularly difficult to eradicate because of its ability to reproduce through seeds and root suckers. New shoots can emerge from its extensive root system, meaning simply cutting down an established tree may trigger vigorous regrowth.

Tree of heaven can also suppress neighbouring vegetation through allelopathy, releasing chemicals that inhibit the growth of some other plants. As dense populations develop, native plants can be crowded out and habitats can be altered.

Why do spotted lanternflies prefer it?

The spotted lanternfly, Lycorma delicatula, is native to parts of Asia and was first detected in the US in 2014. The insect feeds on sap from a wide range of plants, but tree of heaven is one of its preferred hosts.

Spotted lanternflies use their specialised, straw-like mouthparts to suck plant sap. They can feed on numerous agricultural, ornamental and forest plants, with grapes being particularly important from an economic perspective. Heavy feeding can stress plants, while the sugary honeydew produced by the insects can encourage the growth of sooty mould.

The close association with tree of heaven is significant because the invasive tree is already widespread. Its abundance can provide spotted lanternflies with suitable feeding sites, potentially supporting local populations.

The surprising trap-tree strategy

Rather than removing every tree of heaven immediately, one approach is to retain a limited number as trap trees.

The principle is simple. Since spotted lanternflies are strongly attracted to tree of heaven, selected trees can be retained and monitored as locations where the insects are likely to congregate. Researchers and land managers can then target the insects on those trees.

Penn State Extension says some tree of heaven can be left standing and treated with a systemic insecticide so that spotted lanternflies feeding on the trees are exposed to it. Where trees are retained, the guidance recommends keeping male trees where possible to avoid additional reseeding.

US Department of Agriculture research has also identified tree of heaven as the preferred host for placing traps used to detect spotted lanternflies.

Why removing the tree is still important

Using selected trees as traps does not mean tree of heaven should be allowed to spread. The invasive plant itself causes environmental problems and can establish dense populations that displace native vegetation.

Penn State Extension notes that eliminating tree of heaven may also help reduce spotted lanternfly populations at a particular location, although the relationship is complex and more research is needed to determine the impact of tree removal on nearby spotted lanternfly populations.

The broader strategy is therefore to manage both invasive species together rather than treating them as completely separate problems.

Why simply cutting it down can make things worse

Tree of heaven has a remarkable capacity for regrowth. Cutting an established tree without properly treating its root system can result in new shoots emerging from the stump and roots.

Penn State Extension recommends targeting the root system when controlling established trees. Depending on the situation, management can involve foliar, basal-bark or hack-and-squirt herbicide applications. The organisation advises treating the tree before cutting it and allowing time for the treatment to work.

Young seedlings can sometimes be removed by hand when the soil is moist, but care is needed to remove the entire root system because small root fragments can produce new shoots.

What about the 'poisonous sap' claim?

Tree of heaven does contain compounds that can make it unpalatable to some animals, but describing its sap simply as a poison that protects the tree from birds oversimplifies the science.

The tree contains defensive chemicals, while spotted lanternflies have evolved to feed successfully on it. Penn State also warns that people can experience skin irritation after contact with parts of the tree, and rare cases of more serious reactions have been reported following sap exposure through broken skin. Protective clothing and gloves are recommended when handling the plant.