The Spotted Lanternfly (Lycorma delicatula) is an invasive planthopper native to Asia that has rapidly become an agricultural and urban pest since its detection in the United States in 2014. This insect feeds on the sap of a wide variety of plants, including valuable crops like grapes and hops, as well as many tree species. Understanding its daily and nightly routine is important for residents and land managers in affected areas to effectively limit its spread and impact. The question of where these insects go after sunset is a practical one, as their nocturnal habits reveal a predictable behavior that can be exploited for control.
The Daily Cycle of Spotted Lanternflies
During the daylight hours, the Spotted Lanternfly is highly active, primarily focused on feeding and movement. The insects use piercing-sucking mouthparts to extract sugary sap from the phloem of host plants. This feeding behavior is often concentrated on the woody trunks and branches of trees, especially for fourth-instar nymphs and adults.
The insects are in near-constant motion when they are not feeding, exhibiting active flight, hopping, and climbing. Nymphs, which cannot fly, move by climbing up plants and then jumping or falling to disperse. Adults are winged but often prefer to walk up vertical surfaces, a behavior that is visually guided by vertical silhouettes like tree trunks and poles. This activity peaks during the day but begins to change as the evening approaches.
Nocturnal Roosting and Vertical Migration
As temperatures drop and light levels fade, the high-energy feeding and dispersal of the day transition into a predictable, consolidated resting phase. This change in behavior is often described as vertical migration, where the insects adjust their position on the host plant. This movement helps the insects regulate their body temperature and find sheltered spots for the night.
Adult lanternflies cease feeding and move downward along the host tree trunks toward the base. They aggregate in large numbers, often forming dense clusters near the soil line or on the lower portion of the trunk where the bark is rougher. This aggregation is a key feature of their nocturnal behavior, as they seek out less exposed locations.
The insects cluster not only on the host tree but also on nearby structures that offer a vertical surface, such as fences, stone retaining walls, or lawn furniture. These locations provide shelter and are also the sites where females often lay their egg masses from late summer through the first hard freeze. The concentrated numbers and relative immobility of the insects at night create a window of opportunity for focused action.
Using Nighttime Behavior for Management
The predictable, aggregated nature of the Spotted Lanternfly at night allows for highly targeted and efficient control efforts. Since the insects consolidate their numbers on the lower parts of tree trunks and nearby objects, they are easier to locate and contain. This predictable clustering is especially noticeable at dusk and throughout the night.
Methods like trunk banding take advantage of the insect’s tendency to move up and down the tree trunk, trapping nymphs as they attempt to climb. For adults, their reduced mobility at night makes mechanical removal highly effective; individuals or large clusters can be scraped, vacuumed, or crushed. The insects are less likely to jump or fly away when they are settled for the night.
Localized pesticide application is more efficient when the insects are consolidated on specific surfaces. Contact insecticides can be applied directly to the surfaces where the lanternflies aggregate, such as the base of a preferred host tree or a frequently used structure. This targeted approach conserves resources and reduces the potential impact on non-target organisms compared to broad-area spraying.