About the Lab
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, and viruses are submitted to the lab by DATCP inspectors and field specialists who are trained to recognize disease symptoms. The lab uses microscopy, culturing, enzyme-linked immunosorbent assay (ELISA), polymerase chain reaction (PCR), and sequencing to identify pests and pathogens.
In 2023, the lab processed 626 plant samples for diseases and 50 plant samples for insect and mite concerns in support of DATCP's statewide surveys and regulatory inspections. In addition, 1,344 insect trap samples were screened for regulated and non-native pests. The lab conducted a total of 1,882 tests on the 626 plant samples processed for diseases.
As a member laboratory in the National Plant Diagnostic Network (NPDN), the Plant Industry Bureau Laboratory represents Wisconsin as part of an extensive diagnostics system of labs throughout the United States. The NPDN system of more than 70 labs protects national plant health by providing accurate, rapid pest and disease identification and reporting.
Current Topics
In addition to providing diagnostic services, the lab carries out surveys targeted at specific exotic pathogens and nematodes identified as national or state priority pests. Below are the summaries of recent survey projects.
New State Records
Lab testing first confirmed new state records for the pathogens
Gymnosporangium yamadae (the causal agent of red star rust) and
Erysiphe viburniphila (a powdery mildew species) in 2021. In 2022,
G. yamadae was documented in eight more counties by DATCP and the UW-Madison Plant Disease Diagnostics Clinic. Red star rust has now been confirmed in Dane, Kenosha, Milwaukee, Outagamie, Ozaukee, Portage, Racine, Sheboygan, and Waukesha counties, on both nursery stock and landscaped trees. The prevalence of cases in the last two years indicates that this invasive disease of apple, crabapple, and juniper may be widely distributed in the state. In addition, a second detection of the powdery mildew
Erysiphe viburniphila on viburnum was confirmed in Washington County in 2022. This species had previously been recorded in Adams County.
Learn more about the recent detections of
red star rust and
powdery mildew.
Community Garden Solanaceous Virus Survey
In 2023, DATCP plant pathologists conducted a survey of 10 Dane County community gardens for tomato brown rugose fruit virus (ToBRFV) and potato spindle tuber viroid (PSTVd). Ninety-six potato, pepper, and tomato leaf samples were collected across the 10 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.
Potato Mop Top Virus Survey
Potato mop top virus (PMTV) was detected for the first time in a Wisconsin-grown potato tuber in 2020, prompting DATCP to conduct a two-year survey for PMTV and its vector,
Spongospora subterranea f. sp.
subterranea (the fungus-like organism that causes powdery scab). Both PMTV and powdery scab are of economic importance to potato production. Potato mop top virus compromises tuber quality and contributes to total virus load. Seed potatoes are ineligible for certification if allowable virus limits are exceeded. The powdery scab pathogen was included in the survey because it vectors PMTV, its survival and persistence in the soil, and lack of effective control options. The multiyear survey included tuber sampling in 2021 and soil sampling in 2022.
Lab testing found no PMTV in the combined 309 tuber and soil samples collected from potato growing areas of Wisconsin. Powdery scab was identified in nine tubers from 103 lots sampled in 2021 and in 70 soil samples from 206 potato production fields sampled in 2022.
Learn more about the Potato Mop Top Virus Survey.
Nursery Pathway Pest Survey
DATCP pest survey staff conducted a risk-based nursery pathway survey at 17 nursery and garden center locations across 10 southcentral and southeastern Wisconsin counties in 2022. The purpose of the survey was to increase surveillance of 19 priority pests at heightened risk of entering the state through the nursery trade.
All symptomatic plant samples and insect trap collections were submitted to the Plant Industry Bureau Lab for testing and screening for target organisms. Laboratory analysis of 410 insect trap samples found no target insects. In addition, testing of 18 symptomatic plant samples collected as a result of visual surveys (including 17 target disease suspects and one target insect suspect) found a single target organism: Gymnosporangium yamadae (red star rust). This rust species was confirmed on crabapple and apple at two sites in Dane County and one site in Sheboygan County.
Learn more about the Nursery Pathway Pest Survey.
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Viruses of Nursery Ornamentals
Inspectors collected 136 ornamental plant samples for virus testing at the lab. Tobacco
rattle virus (TRV) was detected most often, with 62 positives (mainly in
astilbe, bleeding heart, hosta, and peony). Potyviruses were confirmed in iris,
rose, sedum, and wisteria, for a total of nine positive samples. In addition,
hosta virus X was found in nine hosta samples, cucumber mosaic virus (CMV) was
detected in astilbe, lobelia, and monkshood, and Ilarviruses were confirmed in
five samples.
Other
virus finds included impatiens necrotic spot virus in begonia; alfalfa mosaic
virus in phlox; and tomato ringspot virus in lily. Several plants co-infected
with two viruses were also observed: astilbe ‘Fanal’ with Ilarvirus and TRV;
astilbe ‘Bridal Veil’ with Ilarvirus and TRV; Joe-Pye weed with Ilarvirus and
TRV; and lobelia ‘Monet Moment’ with CMV and TRV.
Learn more about the symptoms plant viruses cause on ornamental plants in our Gallery of Ornamental Plant Virus Symptoms.
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Status Reports
- Soybean Cyst Nematode in Wisconsin
- Crop Export Certification Testing
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. The PIB Lab tested 120 samples for 108 different plant pathogenic bacteria, fungi, viruses, and nematodes in 2023. Six regulated diseases were detected as part of this testing: brown spot, Goss's wilt, gray leaf spot, northern corn leaf blight, soybean cyst nematode, and wheat streak virus. All regulated diseases detected are known to occur in Wisconsin.
Learn more about the PIB Lab's
Crop Export Certification Testing.
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