Johanna Witzell

Johanna Witzell


Associate professor, Editor-in-Chief Scandinavian Journal of Forest Research


My teaching covers forest pathology, tree resistance and defense against natural enemies, and chemical ecology (SLU Umeå and Alnarp, UmU, Lund Univ.). During my recent affiliation with UEF in Finland (2014-2016), I was course leader for MSc level courses 3513143 "Microbes in trees and wood" (5 ECTS), 3513142 "Basics of wood materials science" (1 ECTS), 3513138 "Thesis Seminar II in Wood Materials Science" (1 ECTS), 3513139 "Master’s Thesis in Wood Materials Science" (30 ECTS). I have organized several PhD courses in my role as a research school coordinator (2008-2013). From February 2019 on, I am responsible for the MSc thesis course at our department.


My research interests include forest diseases, tree resistance and stress responses (with special interest in phenolic defensive compounds), functional traits of fungal endophytes of trees, Dutch elm disease and invasive Phytophthora-species. I am interested in the interface between biology and forest management, e.g., how fertilization influences tree quality, how thinning influences fungal biodiversity, or how the fungal communities can influence tree resistance or regeneration success.

Research in my group is financed by EU MSCA IF grant to post doc researcher Dr. Carmen Romeralo, and MSCA ITN grant to a PhD student (project "PROTECTA", coordinated by Prof. Laura Grenville-Briggs Didymus), by SNS, Swedish Research Council Formas and Carl Tryggers foundation. I collaborate with Dr. Michelle Cleary (SLU; Phytophthora-damages of broadleaved trees), Assoc. Prof. Benedicte Albrectsen (Umeå University, Umeå Plant Science Center; endophytes and tree chemical defenses), Assoc. Prof. Juan A. Martín (UPM, Madrid, Spain; Dutch elm disease, tree endophytes), Prof. Olov Sterner (Lund University; analysis of fungal chemicals) and Dr. Dan Bergström and Prof. Urban Bergsten (SLU; effects of thinning regimes on biodiversity).



Tree and forest diseases interest forest owners, forestry professionals and common public. An important part of my work is to inform about diseases to different target groups in society. 

Recent invited lectures (in Swedish):

Phytophthora: nya skadegörare i våra skogar. Skogskväll - Spillkråkorna och Skog & Lantbruk SEB, Stockholm, 2018-03-22.

Phytophthora – hot mot mångfalden. Naturskyddsföreningen konferens Biologisk mångfald i Skåne, Tyringe, 2017-11-19.

Klimatförändring och skogsskador. Nordgen temadag ”Frø- og planteforsyning i det grønne skiftet”, Asker, Norge, 2017-03-21. 

Framtida hot.  Plantans Dag (Skogforsk), Sundsvall, 2016-11-18 .

In media:

Klimatförändringar slår mot svenska bokskogar. Sveriges Natur 2017-06-20 

Sätt stopp för biologisk bulldozer. Skogen 2017-05-22 

Nya skadegörare hotar svenska lövskogar.  ATL 2017-04-29


Chemical quality of woody plants, based on phenolic metabolites, has been the subject of most my studies since I finished my PhD in Professor Riitta Julkunen-Tiitto’s (UEF, Finland) research group in Finland (1998). My PhD thesis focused on studying the effect of nitrogen fertilization on the growth and phenolic metabolites in dark-leaved willow (Salix myrsinifolia Salisb.). After that, I worked as a post-doctoral fellow in Professor Alan Slusarenko’s laboratory (RWTH Aachen, Germany) where I had a possibility to learn more about the defensive mechanisms in the model plant Arabidopsis.

I came to Sweden in 1999 to work as a post-doctoral fellow in Professor Torgny Näsholm’s group (SLU, Umeå Plant Science Center). In that position, I continued to explore the effects of nitrogen amendments on plant defensive chemistry, but this time the study system was bilberry (Vaccinium myrtillus L.), a keystone species of boreal forests. Between 2002 and 2006, I continued this research an assistant professor, financed by the Swedish Research Council Formas.

In 2006, I moved to Southern Swedish Forest Research Center, where I started to work with Dutch elm disease (collaboration with Prof. Juan A. Martín, UMP Madrid), focusing on the role of endophytic communities in this disease complex. Since 2010, I have also been working with Phytophthora-damages of broadleaved trees, lately in close collaboration with Dr. Michelle Clearly, who recently joined our department and is now leading this line of research. This work includes close contacts with forest owners and common public. Together with Professor Urban Bergsten (SLU Umeå), I coordinated a research school "Sustainable Management and Utilization of Forests" in 2008-2013.

During 2014-2016, I was holding a chair of Professor in Wood Materials Science at my Alma mater, the University of Eastern Finland (80% of full time). My main task in this position was to lead the international MSc program in Wood Materials Science. Since June 2016, I am back at SLU where I continue research on forest tree health and I am also leading a new research school “Bio-economy adapted forest management”, which is a collaboration between several Swedish forest companies and The Faculty of Forest Sciences at SLU.


Currently co-supervisor for three PhD students (Mattias Engman and Adrian Villalobos at SLU, and Diana Eckert at LNU.

I was main supervisor for Marta Agostinelli, who defended her thesis on fungal assemblages in forest trees in December 2018, and for Dr. Kathrin Blumenstein (currently post doc in Georg August University in Göttingen) who defended her thesis on elm endophytes in December 2015. I have been co-supervisor for four completed PhD students in 2005-2013. I have supervised several BSc and MSc thesis projects.

Publikationer i urval

Agostinelli M, Cleary M, Martín JA, Albrectsen B, Witzell J (2018). Pedunculate Oaks (Quercus robur L.) Differing in Vitality as Reservoirs for Fungal Biodiversity. Frontiers in Microbiology, 9:1758, doi: 10.3389/fmicb.2018.01758

Cleary M, Blomquist M, Vetukuri RR, Böhlenius H & Witzell  J. (2017) Susceptibility of common tree species in Sweden to Phytophthora cambivora, P. plurivora and P. cactorum. Forest Pathology 47: e12329. DOI: 10.1111/efp.12329

Anderbrant O, Yuvaraj JK, Martin JA, Gil L, Witzell J (2017) Feeding by Scolytus bark beetles to test for differently susceptible elm varieties. Journal of Applied Entomology 141: 417 - 420 DOI: 10.1111/jen.12354.

Cleary M, Ghasemkhani M, Blomquist M, Witzell J. (2016) First report of Phytophthora gonapodyides causing disease of European beech (Fagus sylvatica) in Southern Sweden. Plant Disease 100(10):2174.

Romeralo C, Witzell J, Diez JJ (2016) Aleppo pine provenances vary in susceptibility and secondary chemical response to Gremmeniella abietina infection. Plant Pathology  65: 664–672.

Kaitera J & Witzell J (2016). Phenolic profiles of two Melampyrum species differing in susceptibility to Cronartium rust. European Journal of Plant Pathology 144: 133-140.

Romeralo C, Witzell J, Romeralo-Tapia R, Botella L & Diez J (2015). Antagonistic activity of fungal endophyte filtrates against Gremmeniella abietina infections on Aleppo pine seedlings. European Journal of Plant Pathology 143: 691-704. 

Blumenstein K, Macaya Sanz D, Martín JA, Albrectsen BR & Witzell J (2015) Phenotype Microarrays as a complementary tool to next generation sequencing for characterization of tree endophytes. Frontiers Microbiology 6:1033.

Gunulf A, Witzell J and Rönnberg J (2015). Risk of false positives during sampling for Heterobasidion annosum s.l. Plant Disease 100: 175-179. 

Martín JA, Macaya-Sanz D, Witzell J, Blumenstein K, Gil L (2015). Strong in vitro antagonism by elm xylem endophytes is not accompanied by temporally stable in planta protection against a vascular pathogen under field conditions. European Journal of Plant Pathology 142: 185-196.

Blumenstein K, Albrectsen B, Martín JA, Hultberg M, Sieber T, Helander M, Witzell J (2015) Nutritional niche overlap potentiates the use of endophytes in biocontrol of a tree disease. BioControl 60: 655-667.

Popular science publications (in Swedish)

Witzell J & Cleary M (2017) Hantering av Phytophthora i sydsvenska lövskogar.  

Blomquist M, Cleary M, Witzell J (2016). Phytophthora på frammarsch i sydsvenska lövskogar. Ekbladet. 31: 19-24.

Witzell  J  & Cleary  M (2014).  Askskottsjuka - ett slag mot ädellövskogsbruket  Ekbladet 29: 19-27.

Witzell  J  & Anderbrant  O (2013).  Almsjuka – en berest skadesvamp på långbesök. Ekbladet 28: 13-19.