The spotted lanternfly (Lycorma delicatula) is an invasive insect that was first detected in the United States in 2012, in Pennsylvania.
It is native to China, India, and Vietnam, and has been accidentally introduced to other countries, such as South Korea and Japan.
The insect feeds on tree and plant sap and has been known to harm fruit trees, grape vines, and hardwood trees such as oak and maple.
According to new research, the spotted lanternfly may not be as harmful to hardwood trees as previously thought.
How does the spotted lanternfly affect trees?
Michael M. Santiago/Getty Images
The spotted lanternfly has piercing and sucking mouthparts that it uses to suck the phloem sap out of plants.
Phloem sap is the sugary liquid that transports nutrients and hormones throughout the plant. By feeding on the phloem sap, the spotted lanternfly can reduce the plant's ability to photosynthesize, grow, and reproduce.
The insect also excretes a large amount of honeydew, a sticky substance that attracts other insects and fungi and can cause sooty mold to grow on the plant's leaves and stems.
The spotted lanternfly has a preference for the tree of heaven (Ailanthus altissima), a non-native invasive tree that is widespread in the northeastern U.S.
However, it can also feed on more than 70 other plant species, including many native and economically important trees such as maple, willow, birch, walnut, apple, peach, grape, and hops.
Previous studies have reported that the spotted lanternfly can cause significant damage to these trees, especially when they are exposed to high densities of the insect for prolonged periods of time.
A new study challenges the assumption of spotted lanternfly damage to hardwood trees
A new long-term study led by Penn State University has challenged the assumption that the spotted lanternfly poses a serious threat to hardwood trees in the northeastern U.S.
The study, published in the journal Environmental Entomology on August 29, 2023, aimed to assess the long-term effects of spotted lanternfly feeding on hardwood trees.
The researchers constructed large enclosures containing various tree species, including the insect's favorite food, the tree-of-heaven, as well as native trees such as silver maple (Acer saccharinum), weeping willow (Salix babylonica), and river birch (Betula nigra).
Some enclosures contained tree-of-heaven to study its impact on the feeding pressure on native hardwoods.
Researchers exposed trees to various densities of spotted lanternflies throughout their lifecycle, from eggs to adults, in these enclosures.
They monitored various factors, such as leaf gas exchange, nutrient concentrations important for photosynthesis and growth, and tree diameter growth over four years.
The study found that increased feeding pressure from spotted lanternflies led to reduced levels of key nutrients, such as nitrogen and phosphorus, which significantly affected tree diameter growth during the first two years when feeding pressure was most intense.
However, when feeding pressure was reduced in the third year, native trees recovered while tree-of-heaven growth remained stagnant. There were no significant differences in leaf gas exchange between the treatments.
The study is based on the worst-case scenario, in which spotted lanternflies fed on the same trees for four consecutive growing seasons.
Researchers do not expect significant negative effects on forest or ornamental trees in natural settings where these insects move frequently among host trees.
Kelli Hoover, a professor of entomology at Penn State and the lead author of the study, emphasized that these findings could offer relief to growers and suggested that the cost of treating trees with insecticides might not be justified given the insects' mobility.
Implications and limitations of the study: What does it mean for tree health and management?
The study provides new insights into the potential effects of spotted lanternfly feeding on hardwood trees in the northeastern U.S. and suggests that these trees may be more resilient than previously thought.
The study also highlights the importance of considering multiple factors, such as insect density, host preference, nutrient availability, and environmental conditions, when evaluating the impact of invasive insects on plants.
However, the study also has some limitations that need to be addressed in future research. For instance, the study only focused on four species of hardwood trees and did not include other important species such as oak or walnut.
Moreover, the study did not measure other aspects of tree health or productivity, such as leaf area, biomass accumulation, fruit yield, or quality.
Additionally, the study did not account for possible interactions between spotted lanternflies and other pests or pathogens that may affect tree health or performance.
Therefore, more research is needed to fully understand how spotted lanternflies affect different types of trees and plants in different settings and scenarios.
Furthermore, more efforts are needed to prevent or control the spread of this invasive insect, which poses a serious threat to agriculture and biodiversity in the U.S. and beyond.
