The Plant Industry Bureau Laboratory provides plant pest and disease diagnostic services to the bureau's programs and conducts early detection surveys for diseases of economic and regulatory significance. Plant samples with diseases caused by bacteria, fungi, nematodes, viruses, and other microorganisms are submitted to the lab by DATCP inspectors and survey specialists trained to recognize disease symptoms. The lab uses microscopy, culturing, enzyme-linked immunosorbent assay (ELISA), lateral flow device (LFD), polymerase chain reaction (PCR), recombinase polymerase amplification (RPA) and sequencing to identify pests and pathogens.
In 2025, the lab processed 491 plant samples for diseases and 54 plant samples for insect and mite concerns in support of DATCP's statewide surveys and regulatory inspections. In addition, 1,027 insect trap samples were screened for regulated and non-native pests. The lab conducted a total of 2,250 tests on the 491 plant samples processed for disease identification.
The PIB Lab participates in the USDA-APHIS-PPQ Science and Technology's Plant Pathogen Diagnostics Certification Program which provides proficiency certification to participating labs for the lab techniques real-time PCR, conventional PCR, ELISA, manual DNA extraction, and semi-automated DNA extraction, as well as for pathogen-specific results interpretation. In 2026, the PIB Lab has two diagnosticians certified for conventional PCR, real-time PCR, manual DNA extraction, and
Phytophthora ramorum real-time PCR assay interpretation. Participation in this program is a requirement for testing PPQ regulated samples such as
Phytophthora ramorum suspect samples.
In addition to providing diagnostic services, the lab carries out surveys targeted at specific exotic pests and pathogens identified as national or state priority plant pests of concern. Below are the summaries of recent survey projects.
Tradescantia mild mosaic virus
This is the first report of tradescantia mild mosaic virus in the United States. This virus was previously reported infecting
Tradescantia spp. in Germany, Hungary, Italy, and New Zealand. Infected Tradescantia ‘Zwanenburg Blue’ plants brought in from out of state were intercepted, removed from sale, and destroyed at two different nurseries in Washington County, Wisconsin. The identification was made at the PIB Lab and confirmed by USDA’s Plant Pathogen and Confirmatory Diagnostics Laboratory. The infected plants were co-infected with tobacco rattle virus, a very common virus detected in ornamentals. Plants showed symptoms of leaf distortion, chlorosis, necrosis, and flower breaking. The PIB Lab will monitor for tradescantia mild mosaic virus in 2026.
Juniper Mortality
The lab detected juniper mortality, a disease caused by the oomycete plant pathogen
Phytophthora austrocedri, for the first time in Wisconsin. This disease, first detected in North America at two Oregon State nurseries in 2024, was previously only reported in Argentina and the U.K.
Phytophthora austrocedri infects plants in the Cupressaceae family, including native common juniper, creeping juniper, eastern redcedar, and northern white-cedar, in addition to common nursery plants such as arborvitae, juniper, and false cypress. In Wisconsin, it was detected in a planting of ‘Star Power’ junipers at a Washington County nursery. As a safeguarding measure, the field of 720 junipers were removed and burned in early October 2025 with full cooperation of the nursery. Excessive rainfall in August of 2025 and Phytophthora’s affinity for movement in saturated soils makes movement of this pathogen into neighboring fields a concern. In response, DATCP plans to monitor the field and neighboring fields for signs of disease development in 2026.
Elderberry Virus C and Elderberry Virus D
Lab testing conducted at the University of Missouri Plant Diagnostic Clinic confirmed new Wisconsin state detections of elderberry virus C and elderberry virus D. These two viruses were found co-infecting one elderberry plant.
Pacific Coast Pear Rust
In 2025, an interception of the Pacific coast pear rust, caused by the rust fungus Gymnosporangium libocedri, was confirmed by the PIB Lab on a serviceberry (Amelanchier sp.). This heteroecious rust requires incense cedar (Calocedrus decurrens) and a host plant from the Rosaceae family to complete its lifecycle. Although sold in the nursery trade, incense cedar is seldom grown in Wisconsin, making establishment of this pathogen unlikely in the state. In addition, the nursery pruned out all infected plant material and burned it on site, removing inoculum from the site. Species-level confirmation of rusts, such as this one, provides additional value to growers and regulators because of the close relationship between rusts and their hosts.
Recent Surveys
Cereal Cyst Nematode Survey
During 2022 and 2024, soil was collected from 259 fields across 20 counties for screening and molecular testing for cereal cyst nematodes. In 2025, PIB Lab staff analyzed these samples for exotic cereal cyst nematodes.
The targets of this survey were the cereal cyst (Heterodera avenae), exotic cereal cyst (Heterodera filipjevi), the Mediterranean cyst (Heterodera latipons), and the false root-knot nematode (Nacobbus aberrans). In addition to screening and testing for these species, staff recorded other cyst nematodes species detected during the survey.
No exotic cyst nematodes were detected in any of the fields sampled. Seven fields had soybean cyst nematodes (Heterodera glycines), and 21 fields had soybean cyst-like nematodes. Soybean cyst and soybean cyst-like nematodes (such as clover cyst nematode) are known to be present in Wisconsin and can cause yield losses in host crop plantings.
Learn more about the Cereal Cyst Nematode Survey.
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Community Garden Solanaceous Virus Survey
In 2024, DATCP plant pathologists conducted a survey of five Milwaukee County community gardens for tomato brown rugose fruit virus (ToBRFV) and potato spindle tuber viroid (PSTVd). Fifty potato, pepper, and tomato leaf samples were collected across the five gardens. Samples were tested at the DATCP PIB Lab and there were no detections of ToBRFV or PSTVd.
Learn more about the
Community Garden Solanaceous Virus Survey.
Invasive Conifer Pest Survey
Each winter, DATCP conducts visual surveys to detect invasive, conifer-killing pests such as balsam woolly adelgid (Adelges piceae), elongate hemlock scale (Fiorinia externa), and hemlock woolly adelgid (Adelges tsugae, HWA). Visual surveys scanned hemlock and balsam fir trees for signs and symptoms of these pests and recorded locations of 178 areas with hemlock to inform future survey planning efforts. Samples were collected from several sites and screened in the PIB lab.
None of these pests were found in 2025 surveys, which spanned from Milwaukee County in the south up to Ashland County in the north. DATCP will continue to monitor for future introductions, including the addition of eDNA surveys for HWA in 2026, due to the close proximity of these pests in Michigan.
Manoomin (Wild Rice) survey collaboration with Wisconsin Tribal Conservation Advisory Council
Manoomin (Zizania palustris), also known as northern wild rice, is an important traditional food and cultural resource of upper Midwest Indigenous peoples. Recently, Tribal Nations across the upper Midwest have noticed a decline in the health of wild rice beds and an increase in disease symptoms. In 2025, the
Wisconsin Tribal Conservation Advisory Council (WTCAC) conducted a PPA 7721 funded survey to identify diseases found in upper Midwestern manoomin beds. The PIB lab partnered with WTCAC as a contract lab to provide disease diagnostic support for the survey.
Wild rice samples were collected by Tribal representatives and submitted to the PIB lab. Survey targets were bacterial blight (Xanthomonas oryzae pv. oryzae), bacterial leaf streak.(Xanthomonas oryzae pv.
oryzicola), and fungal brown spot (Bipolaris oryzae). Bacterial blight and bacterial leaf streak are serious pathogens of rice and are on the USDA Select Agents list. They have never been reported in the United States. Fungal brown spot is a common disease of manoomin that causes lesions and significantly reduces yields. Other diagnostic work completed included the identification of fungal leaf spots and insect damage present on the samples. The diagnostic information was provided to WTCAC and the sample submitters for their use in better understanding and managing disease in wild rice beds.
Pine and Oak Commodity Survey
Supported through a Plant Protection Act (PPA) 7721 Cooperative Agreement, DATCP conducted a trapping survey for 11 non-native pine and oak pests in 15 eastern Wisconsin counties in 2025. Sites were chosen based on proximity to major rail lines and transportation routes which pose a high-risk pathway into the state. Survey targets included five defoliator moths, black-arched tussock moth (Lymantria monachal), oak processionary moth (Thaumetopoea processionea), pine-tree lappet (Dendrolimus pini), rosy moth (Dryocampa rubicunda), and Siberian silk moth (Dendrolimus superans) and six wood-boring beetles, black fir sawyer beetle (Monochamus urussovii), black spruce beetle (Tetropium castaneum), brown spruce longhorned beetle (Tetropium fuscum), European spruce bark beetle (Ips typographus), large pine weevil (Hylobius abietis), and six-toothed bark beetle (Ips sexdentatus). None of the 11 target pests were detected in the 105 survey traps. In total, 840 individual trap collections were screened in the PIB lab, resulting in the identification of 1,972 longhorned beetles and 6,532 bark and ambrosia beetles by DATCP’s forest entomologist. These 2025 results align with the outcomes of similar surveys in 2021, 2023, and 2024 that found no target pine or oak pests in traps set throughout Wisconsin.
In addition, a state priority survey was conducted for the invasive Mediterranean pine engraver (Orthotomicus erosus), a potentially injurious bark beetle that is killing pines in the southwestern US. Traps placed in Milwaukee, Madison, and the Wisconsin Dells did not detect this pest.
Wheat Blast Survey
Surveys in wheat fields across the southern and east-central areas of the state in June 2024 found a high incidence of disease symptoms due to wet spring conditions. DATCP specialists sampled 61 fields June 6-21 in the following counties: Brown, Calumet, Columbia, Dane, Dodge, Door, Fond du Lac, Kewaunee, Manitowoc, Sheboygan, and Winnebago. These 11 counties contain the majority of the wheat acreage in the state. In each field, a sample consisting of 20 wheat heads and leaves was collected for testing at the DATCP Plant Industry Bureau Lab. Fungal diseases were common in the surveyed fields, particularly Fusarium head blight which was found in nearly half of the sites checked (27 fields). Other diseases detected on the wheat samples included Alternaria head mold (seven fields) and rust (10 fields).
All samples tested negative for the wheat blast pathogen
Magnaporthe oryzae Triticum pathotype, a national priority pest predicted to spread through wheat-growing regions of the world under climate change conditions. Wheat blast was first reported in Brazil and has led to locally severe epidemics with up to 100% crop loss in fields in South America (Argentina, Bolivia, Brazil, Paraguay), Africa, and Asia. DATCP targeted wheat blast as part of a USDA APHIS cooperative agreement. To date, this aggressive fungal disease has never been found in Wisconsin.
Inspection Results and Status Reports
Gallery of Nursery Ornamentals
DATCP inspectors collected 135 ornamental samples for virus testing at the lab in 2025. Tobacco rattle virus (TRV) was detected most often, with 38 positives (mainly in astilbe, bleeding heart, hosta, and peony). Dahlia mosaic virus (DMV), confirmed on 23 dahlias, was the second most detected virus. Tobacco streak virus (TSV) was confirmed on 12 astilbes and 5 dahlias. Hosta virus X (HVX) was diagnosed in 11 hosta samples. In addition, potyviruses were confirmed in hosta (1), iris (3), miniature hollyhock (1), phlox (1), and sedum (2), for a total of eight detections.
Other virus finds included alfalfa mosaic virus (1), arabis mosaic virus (1), clematis chlorotic mottle virus (1) cucumber mosaic virus (2), cycas necrotic stunt virus (3), elderberry virus C (1), elderberry virus D (1), impatiens necrotic spot virus (1), lilac leaf chlorosis virus (1), tomato spotted wilt virus (1), and tradescantia mild mosaic virus (2). Laboratory test results are summarized in the
PIB Annual Report.
Learn more about the symptoms plant viruses cause on ornamental plants in our
Gallery of Ornamental Plant Virus Symptoms.
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Insect Pests of Nursery Stock
DATCP inspectors collected 48 plant samples with entomological pest concerns in 2025 from nursery plants, Christmas trees, and cut plant material. Pest identifications included scale insects (15), mites (13), moth borers and defoliators (8), aphids (5), adelgids (5), thrips (4), weevils (3), galls and leafminers (3), plant bugs (2), and earthworms (1). Multiple regulated and non-native species with out of state origins were identified in the lab, including elongate hemlock scale (Fiorinia externa), hemlock wooly adelgid (Adelges tsugae), Japanese maple scale (Lopholeucaspis japonica), cryptomeria scale (Aspidiotus cryptomeriae), and jumping worm (Amynthas or Amynthus spp.). In many cases the identification of these regulated and non-native arthropods led to their eradication through plant destruction and removal from sale, helping to prevent establishment in the Wisconsin landscape.
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Soybean Cyst Nematode Status Report
Since soybean cyst nematode's (SCN) first detection in the state in 1981, DATCP has maintained a record of new county level detections. In 2023, Barron County had its first detection of SCN, making it the 54th County in Wisconsin with a detection.
Learn more about SCN and its statewide distribution in the
Soybean Cyst Nematode Status Report.
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Crop Export Certification Testing
Exports of agricultural, fruit, ornamental and vegetable crops grown for seed or plants-for-planting are inspected during the growing season for regulated plant pests. DATCP provides annual field inspection and lab testing services to meet phytosanitary certification requirements.
In 2025 the Plant Industry Bureau Lab tested 127 samples from 16 host crops for 136 different bacterial, fungal, viral diseases and nematodes. Several regulated corn diseases were detected, including anthracnose (Colletotrichum graminicola), brown spot (Physoderma maydis), common corn smut, Goss's wilt, grey leaf spot, Northern corn leaf blight, stalk rot (Fusarium subglutinans and
Gibberella fujikuroi), and sugarcane mosaic virus. One regulated carrot disease, leaf spot (Cercospora carotae), was also found. All these diseases are known to occur in Wisconsin.
Learn more about the PIB Lab's
Crop Export Certification Testing.
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