About

Dean Malvick is a Professor in the Department of Plant Pathology at the University of Minnesota. He holds a PhD in plant pathology with a minor in microbial ecology from the University of Minnesota, earned in 1997, a Master's degree in botany and plant pathology from Oregon State University in 1987, and a Bachelor's degree in biology from Bemidji State University in 1983. His research focuses on the biology and management of fungal and Oomycete plant pathogens and their interactions with plants. He aims to improve disease management and diagnosis through problem-solving research and to discover new knowledge on the biology and ecology of important plant pathogens to develop and implement improved disease management strategies. His work involves determining characteristics of pathogen populations, understanding associations and interactions between fungal pathogens and soybean at the organismal level, and developing and validating molecular diagnostic techniques for detecting plant pathogens. His research is conducted across laboratory, growth chamber, greenhouse, and field environments, with recent work on soybean diseases such as sudden death syndrome, brown stem rot, and root rots, as well as Goss’s wilt of corn. In addition to his research, Dr. Malvick is responsible for developing and delivering extension education programs aimed at producers, extension educators, and other agricultural professionals, focusing on the occurrence, characteristics, and management strategies of crop diseases using effective, economic, and environmentally sound methods.

Research topics

• Agronomy
• Biology
• Biotechnology
• Ecology
• Computer Science
• Geography
• Library science
• Pathology
• Medicine
• Horticulture

Selected publications

• First Report of Curvularia Leaf Spot of Corn Caused by <i>Curvularia lunata</i> in Minnesota

  Plant Disease · 2026-01-05

  articleOpen accessSenior author

  In early September 2025, small, round to oval, tan lesions 1 to 3 mm in diameter and surrounded by a brown margin were observed on leaves of field corn (Zea mays L.) in Ramsey County, Minnesota. The lesions were in the upper canopy, with 1 to 5 lesions per leaf in the observed plants. Symptomatic leaves were collected, and spores were obtained from within the lesions. Spores observed under a microscope appeared curved with three septa, smooth and melanized, 20 to 27 μm in length and 8 to 12 μm wide at the broadest part (n = 4). The symptoms on the leaves matched those of Curvularia leaf spot of corn, and the conidia resembled the morphology of Curvularia lunata isolated from corn in the United States (Garcia-Aroca et al. 2018; Anderson et al. 2019; Henrickson and Koehler 2022; Jimenez Madrid 2022; Moparthi and Kleczewski 2023). To isolate the fungus, individual spores removed from lesions were cultured on potato dextrose agar amended with 12.5 mg/L rifampicin (PDAR) and grown at 25 °C in darkness. At 10 days, the colony of the representative isolate Cl1MN was dark brown, with white and gray on top and orange to reddish margins. Conidia were as described above, 17.5 to 27.5 μm × 9 to 15 μm (n = 20), consistent with the morphology of C. lunata. For further identification, genomic DNA was extracted from the isolate Cl1MN, and the nuclear ribosomal internal transcribed spacer (ITS, PX555854), the translation elongation factor 1-alpha (TEF1, PX529568), and the glyceraldehyde-3-phosphate dehydrogenase (GAPDH, PX529567) regions were sequenced (Manamgoda et al. 2014). BLASTn queries showed that the ITS sequence shared 100% identity with the ITS region of the reference genome of C. lunata strain W3 (PRJNA416716, 563/563 bp) and the isolate DMCC2087 (MG971304, 555/555 bp) used in the first report of C. lunata in the United States (Garcia-Aroca et al. 2018). More than 99% identity was shared with the TEF1 (MG979800, 901/903 bp) and GAPDH (MG979801, 550/554 bp) sequences of C. lunata DMCC2087 and those of the C. lunata W3 genome (TEF1, 900/901 bp and GAPDH, 550/554 bp). Maximum Likelihood phylogenetic analysis of concatenated ITS, TEF1, and GAPDH sequences of Curvularia species (Manamgoda et al. 2014) and other available in GenBank further supported the assignment of isolate Cl1MN to C. lunata. A pathogenicity test was conducted with the Cl1MN isolate following methods and conditions reported by Garcia-Aroca et al. (2018). Inoculum was applied to leaves on four plants of each corn line, B73 PI 550473, GC-103-58 RSS, and sweet corn 5456T.54 at growth-stage V4. The same number of plants per line served as non-inoculated controls. Lesions characteristic of Curvularia leaf spot appeared on the inoculated leaves 3 to 4 days after inoculation, similar to those observed on the symptomatic leaves in the field. Symptoms were not observed in the control group. Ten days after inoculation, symptomatic leaf sections (~5 mm²) were excised, sterilized in 0.6% NaOCl, rinsed with sterile water, and air-dried before placement on PDAR and incubation at 25 °C for 5 days in darkness. Characteristics of the reisolate, including colony and conidia morphology, and three sequences were identical to those of Cl1MN and the previous reports of C. lunata in the United States. This confirms for the first time that Curvularia leaf spot of corn caused by C. lunata occurs in Minnesota, adding to the known geographical distribution of this disease and fungus in the United States, which was first documented in Louisiana in 2017 (Garcia-Aroca et al. 2018).

  PublisherOA PDFDOI

• Modeling the environment-related risk of frogeye leaf spot (Cercospora sojina) in soybean across the United States

  Scientific Reports · 2026-04-09

  articleOpen access

  Frogeye leaf spot (FLS), caused by Cercospora sojina, is a common soybean disease across the U.S. Fungicides are a key management tool, particularly when susceptible cultivars are planted; however, widespread QoI resistance has raised concern about overreliance on the remaining effective fungicide classes. Protecting these chemical classes is essential for long-term sustainability, particularly under narrow profit margins. To develop an FLS prediction model that supports more efficient fungicide use, environmental and epidemiological data from multiple site-years were analyzed in 2024 using correlation analysis, logistic regression (LR), and machine-learning approaches. The most effective model combined a 30-day moving average (ma) of daily hours of relative humidity (RH) ≥ 80% and maximum temperature (°C) in a LR model. FLS risk peaked when the 30-d ma of daily hours of RH ≥ 80% was 15–20 h and maximum temperature was 24–36 °C. When daily hours of RH ≥ 80% averaged < 5 h, risk remained low regardless of temperature. Random forest and support vector machine models achieved greater accuracy and sensitivity than LR but showed poorer specificity. This research provides a strong epidemiological foundation for improving decision-making and advancing integrated disease management. The resulting prediction model is deployed in a public decision support system (https://cropprotectionnetwork.org/crop-disease-forecasting), enabling real-time FLS risk assessments and promoting stewardship-minded fungicide use.

  PublisherDOI

• Estimated Soybean Yield and Economic Losses Caused by Diseases in the United States and Ontario, Canada, from 2020 to 2024

  Plant Health Progress · 2025-11-21

  article

  The impact of plant diseases on soybean ( Glycine max [L.] Merrill) yield was estimated across 29 states and Ontario, Canada, from 2020 to 2024 by university and government plant pathologists. Losses from 29 pathogens or groups of pathogens were estimated at the end of each growing season through a survey and summarized across years and locations. Diseases reduced soybean yield by an estimated 1.2 billion bushels (32.8 million metric tons) valued at 14.6 billion USD for the survey period. Per acre, this estimated mean economic loss was equal to 32.93 USD (81.37 USD per hectare) across all locations and years, excluding costs such as fungicide seed treatments and foliar applications. Soybean cyst nematode (SCN) ( Heterodera glycines Ichinohe) reduced yield by 482.4 million bushels (13.1 million metric tons), a value nearly four times greater than the next greatest cause of yield loss, which was sudden death syndrome (SDS) (caused by Fusarium virguliforme O'Donnell &amp; T. Aoki). Following SCN and SDS, the most significant yield losses were attributed to white mold (caused by Sclerotinia sclerotiorum [Lib.] de Bary), seedling diseases (caused by various pathogens), Phytophthora root and stem rot (caused by Phytophthora sojae Kaufm. &amp; Gerd.), and root-knot nematodes ( Meloidogyne spp.), in descending order. The most important diseases in the southern United States were generally different from those in the northern United States and Ontario. The data presented here will enable government agencies, scientists, educators, commodity groups, funding organizations, and plant breeders to enhance and prioritize policy, research, funding, and education regarding soybean disease management.

  PublisherDOI

• Soybean Disease Loss Estimates from the United States and Ontario, Canada — 2024

  2025-03-14 · 5 citations

  report
  PublisherDOI

• Corn Disease Loss Estimates from the United States and Ontario, Canada — 2024

  2025-02-18 · 7 citations

  report
  PublisherDOI

• Progression of Corn Tar Spot and Reproducibility Assessment of an Inoculation Protocol in Semicontrolled Environments

  Plant Disease · 2025-07-08 · 1 citations

  article

  in maize, addressing variability across geographic regions. We tested a whorl inoculation method under semicontrolled environments in Ecuador and the United States, focusing on three objectives: (i) to develop a noninvasive inoculation protocol; (ii) to assess the effects of inoculum source, cultivar susceptibility, and leaf position on disease progression over time; and (iii) to evaluate the reproducibility of the protocol. Inoculum preparations from fresh or stored leaves were tested across multiple maize cultivars. Results indicated that the use of a fresh inoculum source led to faster disease onset (15 to 17 days after inoculation) and higher stromata counts compared with inoculum prepared from stored leaves. In Ecuador, fisheye lesions were prominent, whereas they were absent in the United States; however, the factors driving those differences remain unclear. Reproducibility was high in Ecuador and less consistent in the United States, likely because of environmental variability and inoculum quality. Future research should focus on optimizing artificial inoculation methods by exploring the interaction between environmental conditions, inoculum quality, and host susceptibility. Overall, the findings contribute to refining inoculation protocols for tar spot in maize.

  PublisherDOI

• Management of Soybean Sudden Death Syndrome with Seed Treatments in Northern U.S. Field and Greenhouse Environments

  Plant Health Progress · 2025-01-01

  article1st authorCorresponding

  Sudden death syndrome (SDS) of soybean, caused by Fusarium virguliforme, can significantly reduce soybean yield and is spreading in North America. Soybean cultivars with partial resistance are important for managing SDS, and seed treatments have been developed to supplement resistance and manage SDS where resistance is unavailable. Studies were conducted from 2020 to 2022 at two field locations in Minnesota to evaluate seed treatments containing fluopyram and pydiflumetofen and a biological seed treatment containing saponin extract from Chenopodium quinoa for managing SDS. Both locations had low soybean cyst nematode populations. The average SDS foliar disease index (FDX) severity was 50 and 19% in the untreated plots at the Rosemount and Waseca, Minnesota, field locations, respectively. Pydiflumetofen and fluopyram treatments significantly reduced FDX compared with untreated controls on susceptible and partially resistant soybean cultivars and at each field location. Pydiflumetofen significantly reduced FDX in 75% and fluopyram in 62% of the studies by cultivar. Yield was significantly greater with pydiflumetofen than with other treatments for both cultivars and significantly greater with fluopyram for one cultivar in Rosemount, where SDS severity was the greatest. None of the treatments provided a significant yield benefit in Waseca, where SDS levels were moderately low. Neither seed treatment nor cultivar significantly influenced plant population. In greenhouse experiments with the same treatments, fluopyram, pydiflumetofen, and saponin extract significantly reduced SDS development compared with controls. In summary, seed treatments can be effective for managing soybean SDS across a range of northern field and greenhouse environments with low soybean cyst nematode populations.

  PublisherDOI

• Association of the Pathogen <i>Spiroplasma kunkelii</i> with Corn Stunt Symptoms in Oklahoma, Kansas, Missouri, Arkansas, Nebraska, South Dakota, New York, Wisconsin, Minnesota, Indiana, and Alabama During the 2024 Growing Season

  Plant Health Progress · 2025-01-01 · 3 citations

  article

  Corn stunt is one of the most significant corn diseases in the Neotropics, leading to severe plant stunting and substantial yield losses. Although four pathogens have been found either singly or in combination in infected plants in the Americas, corn stunt spiroplasma ( Spiroplasma kunkelii) has been the most predominant pathogen associated with the disease in the United States, due to its widespread distribution in the Rio Grande Valley region and persistent occurrence in California and Florida. During the 2024 growing season, reports of chlorosis, leaf reddening, and stunting in corn fields in Southern, Great Plains, Central Corn Belt, and Northeastern states raised concern regarding the possibility of a more widespread distribution of corn stunt spiroplasma in the United States. Symptomatic corn leaf samples were collected in commercial and experimental field sites across the United States. Detection and identification of S. kunkelii were performed using a polymerase chain reaction assay targeting a section of the spiralin gene, followed by amplicon sequencing. This study provides the first report of the pathogen S. kunkelii associated with corn stunt symptoms distributed across 6 counties in Oklahoma, 14 counties in Kansas, 2 counties in Missouri and Arkansas, 4 counties in New York, and 1 county in each of Nebraska, South Dakota, Wisconsin, Minnesota, Indiana, and Alabama. All states with submitted samples had at least one confirmed case of S. kunkelii.

  PublisherDOI

• Corn Yield Loss Estimates Due to Diseases in the United States and Ontario, Canada, from 2020 to 2023

  Plant Health Progress · 2025-11-05

  article

  Corn ( Zea mays L.) was planted on 375.1 million acres (151.8 million hectares) cumulative from 2020 to 2023 in the United States and Ontario, Canada. During these 4 years, 59.6 billion bushels (1.5 billion metric tons) of grain were produced, valued at 325.9 billion U.S. dollars (USD). Plant pathogens that cause diseases limit annual grain production and reduce associated economic returns while also increasing management costs to prevent potential losses. Plant pathologists representing 29 U.S. states and Ontario, Canada, were asked to estimate annual percent yield losses caused by 37 pathogens or pathogen groups through an online survey. Grain contaminated by mycotoxins was also estimated. According to survey results, estimated overall annual percent losses ranged from negligible in Texas in 2023 to 15.8% in Michigan in 2021 and averaged 3.0% across all surveyed regions for the 4-year period. Diseases reduced corn yield by an estimated 2.5 billion bushels (63.7 million metric tons) across participating locations, with tar spot (caused by Phyllachora maydis), Fusarium stalk rot (caused by Fusarium spp.), and plant-parasitic nematodes causing the most significant losses. The total estimated economic loss caused by diseases was 13.8 billion USD, and the average economic loss was 37.76 USD per acre (93.30 USD per hectare) across all years and locations. Survey data and the resulting analysis can help inform corn disease management and guide pathology education, policy, and research priorities among scientists, government representatives, Extension educators, and other stakeholders.

  PublisherDOI

• A rapid loop-mediated isothermal amplification assay for the detection of root rot in soybean caused by <i>Phytophthora sojae</i>

  Analytical Methods · 2025-01-01 · 1 citations

  article

  Soybean ( Glycine max ) production is severely impacted by Phytophthora sojae , the causal agent of Phytophthora root and stem rot, resulting in significant yield losses worldwide.

  PublisherDOI

Frequent coauthors

• Martin I. Chilvers

  Michigan State University

  56 shared

• Daren S. Mueller

  Iowa State University

  33 shared

• Damon L. Smith

  University of Wisconsin–Madison

  31 shared

• Kiersten Wise

  University of Kentucky

  30 shared

• Carl A. Bradley

  University of Kentucky

  30 shared

• Crystal M. Floyd

  University of Minnesota

  28 shared

• Alison E. Robertson

  Iowa State University

  28 shared

• Ahmad M. Fakhoury

  Southern Illinois University Carbondale

  26 shared