Remain Vigilant of Invasive Plant Pests Spotted Lanternfly and Winter Moth During the Springtime

Find them, kill them 

The Rhode Island Department of Environmental Management (DEM) is reminding Rhode Islanders to remain vigilant for invasive species as their lifecycles progress and they emerge during the spring.

The Spotted Lanternfly (SLF) and Winter Moth are two invasive species that remain the focus of DEM's Division of Agriculture and Forest Environment's Cooperative Agricultural Pest Survey (CAPS) and Forest Health Program efforts to monitor and limit the spread of pests which represent a tangible threat to Rhode Island’s agriculture and forests. 

First detected in Pennsylvania in 2014, the SLF has established populations in 14 states, including Rhode Island. SLFs are commonly attracted to the invasive Tree of Heaven (Ailanthus altissima) but also threaten many fruit crops such as apples, apricots, cherries, grapes, hops, nectarines, peaches, and plums as well as native maple, oak, pine, poplar, sycamore, walnut, and willow trees. 

Rhode Island is at high risk of this invasive pest that can cause significant damage to agricultural crops and trees and affects the quality of life and enjoyment of the outdoors. 

For many Rhode Islanders, the spring season is a time for outdoor recreation and a time of travel, but the SLF is an excellent hitchhiker that is spread through human movement. Their inconspicuous egg masses can be laid on outdoor recreational equipment including cars, boats and their trailers, campers, grills, and firewood. 

Eggs laid on portable surfaces in the fall can hatch this spring many miles away, so it is important for Rhode Islanders to inspect their gear and vehicles before traveling, even within the state. 

SLF adults lay masses of 30 or more eggs on surfaces ranging from tree trunks to patio furniture, so the public should check trees and surfaces like rocks, metal, outdoor furniture, and fencing for the masses, which are typically 1.5 inches long, greyish brown in color, and resemble clay. 

They can be found on surfaces anywhere from an inch above the ground to 7-8 feet high or above which are typically out of reach. After finding an SLF egg mass, Rhode Islanders should scrape the entire egg mass, using a credit card, paint scraper, or other flat, sturdy tool, into a bottle with isopropyl alcohol to destroy the eggs. 

DEM expects that SLF eggs will begin to hatch in Rhode Island in the coming weeks, as they begin the nymph stage of their lifecycle. Adult SLF emergence is expected to occur in late July and August, which is their most recognizable life stage. 

If Rhode Islanders think they’ve encountered a nymph SLF this spring, they should send reports of suspected sightings to DEM and compare their observation with life cycle photos before squashing it. The public can help prevent widescale infestation by learning more about SLF, including the appearance of its life stages, by visiting DEM’s SLF webpage. 

DEM, USDA Animal and Plant Health Inspection Service (APHIS), URI’s Biocontrol Lab, and other partners continue to move aggressively to detect and treat scattered SLF populations and egg masses to protect Rhode Island’s farms and forests with the goal of controlling SLF spread and not having to resort to large-scale pesticide treatments. 

Spraying for SLFs in Rhode Island started in 2022, and DEM and its partners will continue targeted treatments of trees and bushes infested with SLF with EPA -approved pesticides Bifenthrin and Dinotefuran to limit the spread of this destructive pest. 

State-licensed and insured applicators are trained to apply these products safely while protecting the environment and non-target species. The targeted treatments are not large-scale operations, and the project crew typically consists of one-to-two contracted pesticide applicators targeting several of the most infested areas. 

SLFs have been detected Smithfield, North Providence, Lincoln, Cumberland, Pawtucket, Providence, Johnston, Cranston and Warwick. DEM staff contact local businesses and property owners before spraying takes place. Spraying will be targeted in transportation areas, highly impacted areas, areas of movement, parks, and areas that are closer to agricultural areas. 

DEM is partnering with the Rhode Island Department of Transportation (RIDOT) to gain safe access to highways for further inspection and treatment as these are high risk methods of SLF movement. 

DEM is also working with RIDOT to develop educational training materials for highway and maintenance staff on reporting SLF population observations throughout their active season. The goal of this outreach is to provide tools and resources for those most likely to encounter SLF and in turn bolster the effectiveness of the state’s response. 

Winter moth is an invasive defoliator from Europe that was first detected in New England in the early 2000s. The caterpillars of winter moth feed on the leaves of deciduous trees in early spring after larval hatch. 

Winter moth caterpillars are lime green with creamy-yellow stripes running lengthwise along each side of the body. Preferred hosts include maple, oak, birch, apple, and blueberry. 

Young larvae feed within the leaf and flower buds of their hosts and are often difficult to spot at this stage. Caterpillar frass (or insect droppings) is often easier to observe than the actual caterpillars. 

Apple orchards and blueberry farms should monitor their plants and potentially spray for winter moth between mid-April and mid-May. Although the increased winter moth activity during the past autumn has generated increased public interest, the defoliation associated with winter moths isn’t nearly as damaging or widespread as spongy moth (formerly gypsy moth), as winter moth do not completely strip leaves, typically only causing tree mortality if defoliation is repeated year after.

In 2005, a biological control program to control winter moth with the specialist parasitic fly, Cyzenis albicans, was initiated, following widely successful winter moth biocontrol efforts in Nova Scotia with C. albicans. 

Releases have been conducted throughout Rhode Island and New England and the flies have been established at almost all release sites throughout the region. Levels of winter moth defoliation have declined in the 15 years since initial releases of the flies, indicating a successful biocontrol program. 

While winter moth populations spike from year to year, established populations of C. albicans are expected to build in response to winter moth levels and keep populations in check as DEM continues to conduct aerial surveying to monitor winter moth defoliation. 

Later this year, DEM will be initiating a program to collect C. albicans and redistribute them to areas of winter moth activity in 2025, when the stage of their life cycle is ready for distribution. 

Next week, DEM is hosting an open forum to discuss winter moth and SLF and what DEM is doing to address these two priority plant pests and answer public questions. 

Speakers DEM Forest Health Program Coordinator Alana Russell and DEM Cooperative Agricultural Pest Survey Program Coordinator Cynthia Kwolek will present on the status, concerns, and management response of these two invasive plant pests. The event is in-person only with no virtual option. Registration is required and attendance is limited to 50 people.

WHEN: Wednesday April 10, 10 AM – 12 PM

WHERE: Town Council Chambers, Glocester Town Hall, 1145 Putnam Pike, Glocester, RI 02814

Register here. 

DEM is also offering four educational training sessions at public libraries throughout Rhode Island in early April for green industry leaders, landscapers, nursery owners, farmers, licensed pesticide applicators, and any members of the public interested in learning about how to prepare and respond to SLF. 

Attendees will earn up to two free pesticide credits and will learn how to help protect RI farms and forests by keeping this pest out of vineyards, orchards, and farms that RI’s agricultural economy depends on. 

All four training sessions will cover the same content and will cover strategies for preparing and responding to this destructive invasive pest. These events are free, but registration is required. Please visit www.dem.ri.gov/slf-events for more information and to register.

For more information on DEM programs and initiatives, visit www.dem.ri.gov. Follow DEM on Facebook, Twitter (@RhodeIslandDEM), or Instagram (@rhodeisland.dem) for timely updates.