Spotted Lanternfly in Perspective

Spotted Lanternfly Take Aways

• Spotted lanternfly (SLF) adults prefer tree-of-heaven, but can complete their life cycle by using more than 100 other species. 

• SLF alone rarely kills its host, but it does cause stress to the plant, which can lead to secondary infections and pest problems.

• Current efforts probably won’t keep SLF from reaching our area; however, things can still be done to limit its impact. 

A pair of spotted lanternflies

Dorothy Borowy, Ecologist, Integrated Pest Management Coordinator

The Buzz

News of spotted lanternfly (SLF, Lycorma delicatula) came to the National Capital Area from neighboring Pennsylvania where the pest was first discovered on the heels of emerald ash borer (EAB, Agrilus planipennis) devastation. As SLF publicity and training circulated, the tone from affected areas and industries was urgent, making it easy to draw parallels between EAB and SLF. However, there are few similarities between these two invaders.
Although SLF and EAB are both invasive insect pests, introduced from Asia, that feed on trees (primarily), these pests differ in their host preferences, feeding mode, and life cycle. These critical distinctions mean that SLF and EAB not only have different impacts on forest health, but that strategies for monitoring and managing these pests also differ. Here, we compare current information about the two pests to help put SLF in perspective.

Differences Between Spotted Lanternfly and Emerald Ash Borer

	Spotted Lanternfly	Emerald Ash Borer
Host Preferences	SLF adults and late instar nymphs prefer to feed on the non-native invasive tree-of-heaven (TOH, Ailanthus altissima). However, SLF does not require TOH to complete its life cycle (Uyi et al. 2020). Early instar nymphs are indiscriminate and will feed on a wide variety of native and non-native trees, shrubs, and herbaceous plant species. More than 100 plant species have been identified as hosts for SLF (Barringer & Ciafré 2020).	EAB feeds exclusively on ash trees (Fraxinus spp.). All ash species native to the United States can serve as hosts for EAB. In the National Capital Area, these species include: green ash (F. pennsylvanica), white ash (F. americana), pumpkin ash (F. profunda), and black ash (F. nigra).
Feeding Mode	SLF has piercing-sucking mouthparts, which it uses throughout its life stages to feed on sugar-rich sap. This feeding mode is less invasive than that of EAB. As a result, SLF rarely kills its host. It does, however, cause damage to the plant, including branch dieback, oozing wounds, and leaf wilting. When combined with other stressors, these impacts can overwhelm and kill the host. SLF also indirectly affects plants by secreting honeydew—a sugary substance that collects on vegetation and leaves growing below SLF feeding locations. This honeydew attracts other insects and promotes sooty mold growth, which blocks sunlight from reaching leaves, inhibiting photosynthesis.	EAB has chewing mouthparts, which it uses to feed on different parts of its host tree, depending on life stage. Adults feed on ash leaves, which causes little damage to the tree. EAB poses the biggest threat in its larval stage. Larvae feed on the nutrient-rich vascular tissues (i.e., xylem and phloem), which cuts off water and nutrient transport through the tree, effectively girdling and killing it.
Life Cycle	Life cycle duration: 1 year. Stages: Egg, nymph (4 instars), adult Unlike EAB, spotted lanternfly overwinters as egg masses. The eggs hatch and the first instar nymphs emerge in May-June. The insects molt to progress into each stage. Fourth instar nymphs molt into adults in July-September. Shortly after molting, adults mate and females lay eggs in September-December. Females lay one or two camouflaged egg masses, which look like cracked mortar when dry. Females are not selective and will lay their eggs on almost any surface, from trees and rocks to patio furniture and car wheel wells. Each egg mass contains between 30-60 eggs, arranged in neat rows that are protected from the elements.	Life cycle duration: 1-2 years. Stages: Egg, larvae, and adult Females lay eggs on ash trees from mid-June through August. The eggs are deposited individually in crevices and between the outer bark layers. The eggs hatch in approximately two weeks, depending on the temperature. Newly emerged larvae tunnel through the bark into the cambial region, where they will feed for 1 or 2 years until they mature. Larvae overwinter in their feeding galleries or in pupation cells they construct in the outer sapwood or bark. Mature larvae will stay in their pupation cells through April-May of the next year, gradually developing into adults. Adults emerge from D-shaped exit holes in late May and June and fly into the ash canopy, where they feed on leaves during the day. Mating begins one week after emergence, and females are ready to lay eggs two weeks after mating. Females lay an average of 50 to 150 eggs.

Impacts of SLF: What We Do and Don't Know

Although SLF is not expected to have the same direct impacts on our forest ecosystems as EAB, both pests have a tremendous effect on the local economy. In Pennsylvania alone, where SLF was first identified, the economic impacts of SLF have been estimated at $324 million annually (Harper et al. 2019). These impacts are greatest in the agricultural and hardwood production industries. Large infestations of SLF can dramatically reduce grape, apple, and hop yields, as well as damage economically important hardwood trees including maple, black walnut, cherry, and birch. These impacts have been well-documented in the United States and other countries where SLF has been introduced (e.g., Korea).
The indirect effects of SLF, however, have not been fully assessed and many questions remain. In particular, it’s still not clear how SLF impacts food web structure, how it interacts with other stressors (e.g., climate change and other pests), how the proliferation of sooty mold affects plant growth and survival, and how these secondary and tertiary effects collectively influence forest ecosystem functioning long-term. Because SLF feeds on a wide-variety of plant species and isn’t known to directly kill its host, assessing the full range of ecological impacts from SLF is more difficult than for EAB, which is host-specific and kills nearly 100% of the ash trees it attacks.

Limiting SLF Impacts

It’s unlikely that any current efforts will prevent SLF from reaching our area; however, some things can be done to limit its impact. Numerous studies have shown that promoting forest health and functioning by enhancing native plant species diversity and limiting external stressors is the best strategy for mitigating the impacts of pests and disease in forest ecosystems.
Likewise, staying informed about new research and news updates is key to effectively combating this pest. Local university and county extension offices are valuable resources for learning about a variety of pests, including SLF, as well as for getting up-to-date reports on pest distributions and current research.
These resources are especially important when developing monitoring and management (if applicable) plans for SLF. All projects must consider SLF host preferences, feeding mode, and life cycle to maximize success in limiting the spread of this invasive pest and mitigating its impacts. The most effective monitoring and management efforts for SLF change over the seasons to match the different host preferences and behaviors associated with each life stage (early to late instar nymphs, adults, and eggs). The Penn State Extension has created an SLF management calendar to guide landowners and managers in their efforts and ensure proper timing for different actions. Also, understanding that SLF only prefers TOH in its later life stages and that it can complete its life cycle without this tree species is important for developing targeted efforts that extend beyond monitoring and removing TOH. These efforts include monitoring other host species and signs of SLF (e.g., sooty mold and egg masses) at different times of the year. Finally, please be sure to consult your local and regional Integrated Pest Management and Invasive Plant Management experts when designing SLF monitoring and/or TOH management plans.

Literature Cited

Barringer, L., & Ciafré, C. M. (2020). Worldwide Feeding Host Plants of Spotted Lanternfly, With Significant Additions from North America. Environmental Entomology, 49(5), 999-1011.
Harper, J. K., Stone, W., Kelsey, T. W., & Kime, L. F. (2019). Potential economic impact of the spotted lanternfly on agriculture and forestry in Pennsylvania. The Center of Rural Pennsylvania, Harrisburg, PA.
Uyi, O., Keller, J. A., Johnson, A., Long, D., Walsh, B., & Hoover, K. (2020). Spotted Lanternfly (Hemiptera: Fulgoridae) Can Complete Development and Reproduce Without Access to the Preferred Host, Ailanthus altissima. Environmental Entomology, 49(5), 1185-1190.