Jennifer Juzwik

Title: Research Plant Pathologist
Unit: Biological and Environmental Influences on Forest Health and Productivity
Previous Unit: Understanding & Managing Diseases in Forest Ecosystems
Address: Northern Research Station
1561 Lindig Ave.
St. Paul, MN 55108
Phone: 651-649-5114
E-mail: Contact Jennifer Juzwik

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Education

• University of Minnesota, Ph.D., Plant Pathology, 1983
• Colorado State University, M.Sc., Plant Pathology, 1978
• Fairmont State College, B.Sc., Biology, 1976

Civic & Professional Affiliations

• American Phytopathological Society
• International Society of Arboriculture
• Minnesota Society of Arboriculture
• Northeastern Nursery Association
• Minnesota Shade Tree Advisory Committee

Current Research

As a Research Plant Pathologist, I conduct studies on invasive tree pathogens and associated insects. These studies are often conducted in collaboration with scientists, forest health specialists, and foresters in federal, state and county agencies as well as universities. Practical guidelines ranging from preventing introduction of invasive pathogens to managing or mitigating diseases caused by established pathogens are the outcomes of these studies. I also collaborate with other scientists outside the Station and region to develop effective, economical, and more environmentally benign alternatives to methyl bromide for soil fumigation in U.S. bare-root forest nurseries. My current research efforts concern:

• Hickory decline and dieback research
• Determine frequencies of decline/dieback and mortality of smooth bark hickories in appropriate forest cover types where deviations from expected levels of mortality have been observed (Indiana, Iowa, Minnesota, Ohio, New York, and Wisconsin).
• Quantify relationships between decline/dieback incidence and a) pathogen and/or insect pest presence, and b) prior land use, fire history, soils and drought.
• Determine the role of two newly described Ceratocystis species in decline/dieback and mortality of bitternut hickory.
• Oak wilt research
• Investigate temporal and spatial aspects of belowground transmission of C. fagacearum in relation to current disease management strategies.  These studies include evaluation of the efficacy of propiconazole and of mechanical root graft disruption in operational, oak wilt control programs.
• Evaluate woody shrub and tree regeneration occurring in oak wilt infection centers subjected to different levels of disease management versus non-managed ones

Why is This Important

Oak-hickory forests comprise 29% of the 31 million hectares of forest land in the Upper Midwest (IL, IN, IA, MI, MN, MO and WI).  The oak species group is the most important aggregation of hardwoods in the United States.  Oak decline and oak wilt are responsible for much of the observed oak deterioration and mortality in the midwestern forests.  In addition, new exotic pathogens, such as Phytophthora ramorum (cause of Sudden Oak Death) and Raffaelea quercivora (cause of Japanese oak wilt), are potential threats to the health of oaks in these forests. Our oak disease research addresses both the need for early detection of any unintentionally introduced exotic pathogens and for new or refined management tools for well-established pathogens, such as Ceratocystis fagacearum (cause of oak wilt in the USA).

Hickories are an important component of many forest associations in the eastern United States, particularly various oak-hickory cover types.  Sites impacted by hickory decline or dieback and mortality have recently been reported to lose a high proportion of smooth bark hickories, particularly bitternut, over a very short period of time (3 to 5 years).  These losses cause a significant, adverse impact to wildlife, timber value and biodiversity in affected stands. Our goal is to identify significant biotic and abiotic contributors to the decline or dieback and develop site or silvicultural guidelines for mitigating the tree losses and stand impacts associated with this problem.

Soil fumigation is commonly used in bare-root forest nurseries to manage soil-borne pests including fungal pathogens.  However, bromine resulting from breakdown of methyl bromide – the most commonly used fumigant – contributes to loss of the Earth’s stratospheric ozone layer.  More environmentally benign fumigants are needed for nursery soil treatment.  In addition, information is needed on the potential risk of the alternative fumigants to human and non-target plant health.  My research on chemical fumigants addresses these needs.  The goal is to provide quality tree seedlings for reforestation in the region while minimizing negative impacts to the environment.

Future Research

I would like to develop three areas of interest into research projects in the near future:

• Quantify/determine spatial and temporal aspects of above- and belowground spread of the root and butt rot fungus Heterobasidion annosum in northern pine plantations.
• Assess potential for forest disease epidemics by selected pathogens under different climate change scenarios in the eastern United States.
• Evaluate the relative susceptibility of native US species of Quercus to the exotic, fungal pathogen Raffaelea quercivora.

Featured Publications

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