Plant Industry Bureau Laboratory

​​​​​​​​​​​​​​​​​​​​​​​​​​Tobacco Ring on Tomatoes banner

About the Lab

The Plant Industry Bureau Laboratory pro​​vides 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 s​ubmitted 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. 

2022, the lab processed 942 plant samples for diseases and 89 plant samples for insect and mite concerns in support of DATCP's statewide surveys an​d regulatory inspections. In addition, 617 insect trap samples were screened for regulated and non-native pests. The lab conducted a total of 1,866 tests on the 942 plant samples processed for diseases.

s 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. ​

— Back to Top

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.

ab 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

 — ​Back to Top —​​

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.

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.

— Back to Top —​

Viruses of Nursery Ornamentals

Inspectors collected 154 symptomatic ornamental plant samples for virus testing in 2022. Tobacco rattle virus was detected most often, with 27 positives (mainly in astilbe, bleeding heart, and peony). Potyviruses were detected in hosta, iris, monkshood, phlox, sedum, and spiderwort, for a total of 16 positive samples. Tobacco mosaic virus was found in 10 samples, while five samples were positive for Ilarviruses. Impatiens necrotic spot virus was confirmed in one sample each of begonia, dianthus, and snapdragon.

Other virus finds included alfalfa mosaic virus on arrowwood and peony; clematis chlorotic mottle virus on clematis; cucumber mosaic virus on astilbe, delphinium, and monkshood; hosta virus X on hosta; and lilac leaf chlorosis virus on lilac.​

View our Bugwood Collection of Plant Viruses Symptoms.

— ​Back to Top —​

<< Back to main Pest Survey page