On April 30, 2025, DATCP staff became aware of a report of elongate hemlock scale (EHS) on a hemlock seedling in Wisconsin. The report was submitted by a UW-Stevens Point (UWSP) student on iNaturalist, a social network for sharing observations of biodiversity (image left: hemlock planted at UWSP, credit: iNaturalist). Because EHS is an invasive, non-native pest that Wisconsin has an exterior quarantine for, DATCP immediately investigated the report. DATCP learned Schmeeckle Reserve, a 280-acre conservancy area on the UWSP campus, had planted 50 hemlocks on April 27 which they had recently obtained from a Wisconsin nursery. On May 1, DATCP and UWSP staff worked together to remove all seedlings from three areas at Schmeeckle, finding most infested with EHS, including live immatures (known as crawlers), as well as 10% that were also infested with live hemlock woolly adelgid (HWA).

DATCP followed up with the Wisconsin nursery that sold the seedlings and learned the nursery had purchased 2,200 hemlocks from a nursery in Warren County, Tennessee. Although the Wisconsin nursery had a compliance agreement to import hemlocks from Michigan, they switched suppliers when the Michigan nursery couldn’t fill their order. The Wisconsin nursery surrendered for examination and destruction 275 remaining unsold seedlings to DATCP. They also provided information for 34 customers who purchased hemlock seedlings and immediately reached out to those individuals with instructions to quickly remove and destroy infested seedlings and to offer a credit or refund. DATCP also contacted these customers to share information on HWA and EHS and offered to pick up or help remove any hemlocks that were planted. DATCP tracked and verified all plant material customers destroyed on their own. Material picked up by DATCP staff was examined and found to have a much more significant infestation of HWA, along with the EHS.

DATCP issued a rejection notice to the Tennessee nursery after determining these wild collected hemlocks were not shipped in accordance with State of Wisconsin EHS or HWA exterior quarantine requirements. These quarantines require plant material be officially inspected and certified to be free of regulatory pests, or effectively treated to kill these invasive, non-native insects. EHS and HWA are not known to be established in Wisconsin. Fortunately, no other hemlocks were shipped from this Tennessee nursery to Wisconsin.

As of May 12, a total of 2,185 hemlock seedlings, or 99.3%, have been recovered from the field. DATCP staff are considering this to be a successful “regulatory interception” in which infested material is brought into the state but destroyed before the pest has a chance to establish. Notably, most of the hemlock seedlings were in very poor health. As is standard protocol, DATCP plans to work with partners in coming months and years to perform follow up surveys at sites that received infested stock and have significant amounts of hemlocks or other conifers that may be at risk.

This “close call" highlights the importance of following terms of compliance agreements and quarantines to protect Wisconsin’s native hemlocks, other conifers, and the green industry. DATCP is grateful for the people and actions that led to the early detection and rapid response to this situation, including UWSP students and faculty, the Wisconsin nursery, their customers, and DATCP staff who went above and beyond to track down source information and recover hemlocks from the field. (image right: DATCP forest entomologist collecting an infested hemlock, credit: DATCP J. Oestreich)

Spongy moth (Lymantria dispar) is a non-native insect that has spread throughout the eastern two-thirds of Wisconsin. After establishing in an area, spongy moth can completely defoliate trees and make them vulnerable to death from other environmental stressors. Besides the negative impact to forests, dead trees can decrease property values and require costly removal. Additionally, spongy moth caterpillars’ bristly skins can trigger allergic reactions in humans, including eye, skin, and respiratory system irritation.

DATCP utilizes trapping surveys and treatment to slow the westward spread and impact of spongy moth in Wisconsin as part of the National Slow the Spread Program. Approximately 8,000 traps will be placed in central and western Wisconsin from mid-May to early July both to monitor known spongy moth populations and to find new populations in previously uninfested areas. Aerial treatments will be utilized in targeted areas in western Wisconsin shortly after caterpillars hatch, and again in mid-summer just prior to their mating season.

From mid-May to early June, the planes will spray Bacillus thuringiensis var. kurstaki (Btk), a naturally-occurring soil bacteria which kills spongy moth caterpillars feeding on tree foliage. Btk is not toxic to people, bees, pets, or other animals and is certified for use in organic food production. The following counties are currently scheduled to receive Btk treatments: Buffalo, Grant, and Pepin.

In late June to mid-July, planes will spray an organic, biodegradable spongy moth pheromone to disrupt the mating process. Pheromone treatments spread the scent of female moths over a wide area, preventing male moths from locating real female moths. The following counties are currently scheduled for this mating disruption: Barron, Buffalo, Dunn, Grant, Lafayette, Polk, and St. Croix.

Residents in and near treatment sites can expect to see and hear loud, low-flying planes as early as sunrise. These aerial treatments are the safest, most efficient, and effective methods to slow the moth’s spread and impact westward. However, treatment plans may be adjusted at any time due to unforeseen changes in weather, funding, or other challenges.

An interactive map of the planned treatment areas is available at https://smaerialspray.wi.gov.  To receive up-to-date information on treatment plans, sign up for email updates, call the Spongy Moth Hotline toll-free at (800) 642-MOTH, email spongymoth@wisconsin.gov, or follow us on Facebook or X.

Have you ever encountered an unusual insect or mysterious damage on your plants and just haven’t had a clue? That’s where the UW Insect Diagnostic Lab (IDL) can help!

The IDL was established in 1978 to provide free insect/arthropod diagnostics to Wisconsinites. Each year, the lab fields approximately 2,500 identification requests from Wisconsin’s growers, industry, colleagues in Extension and government, and the general public. This includes hundreds of samples from landscape trees, shrubs, and flowers, as well as nursery stock and greenhouses.

The IDL provides diagnostic services free of charge in most situations. Sample turnaround time is typically one to two business days upon sample arrival in most cases to allow you to respond to emerging pest issues in a timely manner. There are two main ways to get diagnostic assistance at the IDL: digital samples and physical samples. 

• Digital samples: (e., digital photographs) are often the quickest way to get a diagnosis from the IDL and are often a good starting point. When submitting digital photos, please indicate the size of the specimen(s), any relevant clues (e.g., host plant, description of damage, etc.), and where the insect was found (state/county/city). Geographic location can help narrow down possibilities and is also used for record-keeping purposes at the lab to help identify insect trends within Wisconsin.
• Physical samples: While photos can be a good starting point, nothing beats a physical sample under the microscope. In some cases, a definitive diagnosis can only be made with a physical sample. The most important factor is making sure that samples arrive in good condition. Instructions for submitting physical samples to the IDL, as well as a printable sample submission form, can be found here: russell.wisc.edu/samples. 

For additional information about the UW Insect Diagnostic Lab and its services, visit the IDL website at insectlab.russell.wisc.edu. Feel free to contact me (PJ Liesch) at pliesch@wisc.edu or (608) 262-6510 with any specific questions.
--Contributing author PJ Liesch, UW-Madison Dept. Entomology, Insect Diagnostic Lab