Mary Ruth McDonald

Mary Ruth McDonald



519-824-4120 x52791


B.Sc. (Agr.) University of Guelph, Major: Plant Protection;
M.Sc. University of Guelph in Plant Pathology;
Ph.D. University of Guelph in Plant Pathology


Crop Science Building
Muck Crops Research Station


206 CRSC

The research program focuses on work that contributes to integrated crop management of vegetable crops, with the emphasis on crop protection of vegetable crops. The crops of interest are root, bulb, leafy vegetables and crucifer crops, including onions, carrots, lettuce, celery, cabbage, Asian crucifer crops and some minor crops such as artichokes, chives and vegetable amaranth. Recently canola and legume crops have been added. Plant pathology,  disease and insect management and biological control of plant disease are major areas of interest. Collaborative work involving plant physiology, plant nutrition, plant breeding and entomology is also part of the approach.

Specific research projects investigate biological, cultural and chemical means of crop protection to discover the best approaches to crop management and how they interact with host resistance, plant nutrition, production practices, and other insect pests and diseases. Current projects include biology and management of clubroot of crucifer crops, biological control of sclerotia-forming plant pathogens, disease forecasting and management of Stemphyllium blight of onion and asparagus, management of nematodes on vegetable crops, Fusarium on carrots and spinach, and management of onion maggot, carrot rust fly and carrot weevil.  Plant nutrition trials include determining the optimum rates of phosphorous on onions and carrots and evaluating the effects of biochar on crop growth.

The current research program includes trials on specialty crops, such as hops, basil, asparagus and amaranth, conducted at the Simcoe Research Station.  This work focuses on crop production and plant pathology.

Efficacy testing of specific crop protection materials is conducted at the request of the industry.

For further information please visit:


AGR*2470 Introduction to Plant Agriculture
PLNT*6080 Plant Disease Epidemiology and Management

Relevant Links:

Selected Publications:

McDonald, M.R. and J. Warland. Climate change and vegetable crops. (2018). In Agroclimatolgy: Linking agriculture to climate. Editors Jerry Hatfield, Mannava Sivakumar and John H. Prueger. Published by ASA, CSSA, SSSA Books. U.S.A. Submitted.

McDonald, M.R. and G.J. Boland. (2017). Sclerotinia diseases of vegetable crops. In MOfo Branco (White Rot). Editor: David de Souza Jaccoud Filho. Published by Toda Palavra, Brazil. In press.

Yu, Q., E. Ponomareva, D. VanDyk, and M. McDonald. (2017). First Report of the Carrot Cyst Nematode (Heterodera carotae Jones) from Carrot Fields in Ontario, Canada. Plant Disease. In press.

Al-Daoud, F., B.D. Gossen, J. Robson and M.R. McDonald. (2017). Propidium monoazide improves quantification of viable resting spores of Plasmodiophora brassicae with qPCR. Plant Disease. 101: 442-447.

Kong, Y., D. Llewelyn, K. Scheistel, M. Scroggins, D. Lubitz, M.R. McDonald, R. Van Acker, R. Martin and Y. Zheng. (2017). High Tunnels can promote growth yield and fruit quality of bitter melons. HortScience. 52 (1): 65-71.

Gossen, B., J. Dalton, F. Al-Daoud and M. McDonald. (2017). Metabolic Cost of Resistance in Clubroot-Resistant Brassica Crops. Canadian Journal of Plant Pathology. 39: 25-36. DOI: 10.1080/07060661.2017.1292550.

Cranmer,T., B. Gossen, F. Al-Daoud, S. Hwang, and M. McDonald. (2017). Vertical distribution of resting spores of Plasmodiophora brassicae in soil. European Journal of Plant Pathology. DOI: 10.1007/s10658-017-1193-x.

Deora, A., B. Gossen, S. Amirsadeghi and M. McDonald. (2015). Development of a multiplex qPCR assay for detection and quantification of Plasmodiophora brassicae in soil. Plant Disease. 99: 1002-1009.

Gossen, B.D., S. Strelkov, V. Manolii, D. Rennie, T. Cao, S.F. Hwang, G. Peng and M.R. McDonald. (2015). Spread of Plasmodiophora brassicae on canola in Canada, 2003 2014: Old pathogen, new home. Canadian Journal of Plant Pathology. 37: 403-413. DOI: 10.1080/07060661.2015.1105871.

Gludovacz, T., A. Deora, M. McDonald and B.D. Gossen. (2014). Cortical colonization by Plasmodiophora brassicae in susceptible and resistant cabbage cultivars. European Journal of Plant Pathology. 140: 859-862. [Contribution: 40%]

Parker, M., M. McDonald and G. Boland. (2014). Assessing spatial distribution of ascopsoores of Sclerotinia sclerotiorum for regional disease forcasting in carrots. Canadian Journal of Plant Pathology.

Parker, M., M. McDonald and G. Boland. (2014). Evaluation of air sampling and detection methods to quantify airborne ascospores of Sclerotinia sclerotiorum. Plant Disease. 98: 32-42.

Saude, C., P. Simon and M. McDonald. (2014). Incidence and severity of cavity spot of carrot as affected by pigmentation, temperature and rainfall. Plant Disease. 98: 929-936. DOI: 10.1094/PDIS-10-13-1021-RE.

Deora, A., B.D. Gossen, S.F. Hwang, D. Pageau and M. McDonald. (2014). Effect of boron on clubroot of canola in organic and mineral soils and on residual toxicity to rotational crops. Canadian Journal of Plant Science. 94 (1): 109-118.

Saude, C., M. McDonald and S. Westerveld. (2014). NItrogen and fungicide applications for the management of fungal blights of carrot. HortScience. 49 (5): 608-614.

Peng, G., R. Lahlai, S. Hwang, D. Pageau, R. Hynes, M.R. McDonald, B.D. Gossen, and S.E. Strelkov. (2014). Crop rotation, cultivar resistance, and biofungicides/fungicides for managing clubroot (Plasmodiophora brassicae) on canola. Canadian Journal of Plant Pathology. 36: 99-112. DOI: 10.1080/07060661.2013.860398.

Tesfaendrias, M., C. Trueman, B. Gossen, M. McDonald and A. McKeown. (2014). Influence of nitrogen and calcium fertilizers on Septoria late blight and yield of celery. Canadian Journal of Plant Science.

Gossen, B.D., O. Carisse, L.Kawchuk, H. Van Der Heyden and M. McDonald. (2014). The changing landscape of fungicide insensitivity in crop pathogens in Canada. Canadian Journal of Plant Pathology. DOI: 10.1080/07060661.2014.925506.

McDonald, M., K. Sharma, B.D. Gossen, A. Deora, J. Feng and S.F. Hwang. (2014). The role of primary and secondary infection in host response to Plasmodiophora brassicae. Phytopathology. 104 (10): 1078-1087.

Tesfaendrias, M.T., M.R. McDonald and J. Warland. (2013). Long-term Yield of Horticultural Crops in Wisconsin in Relation to Seasonal Climate in comparison with southern Ontario, Canada. HortScience. In press June 2013.

Kasinathan, H., B.D. Gossen, S. Strelkov and M.R. McDonald. (2013). Interaction of pH and temperature affect infection and symptom development of Plasmodiophora brassicae in canola. Canadian Journal of Plant Pathology. In press June 2013.

Deora, A., B.D. Gossen, and M.R. McDonald. (2013). Cytology of infection, development, and expression of resistance to Plasmodiophora brassicae in canola. Annals of Applied Biology. 163: 56–71. DOI: 10.1111/aab.12033.

Lahlali, R., G. Peng, B.D. Gossen, L. McGregor, F. Yu, R. Hynes, S.F. Hwang, M.R. McDonald, S. Boyetchko. (2013). Evidence that the Biofungicide Serenade (Bacillus subtilis) Suppresses Clubroot on Canola via Antibiosis and Induced Host Resistance. Phytopathology. 103: 245-254.

Gossen, B.D., M.R. McDonald, S.F. Hwang, S. Strelkov and G. Peng. (2013). A comparison of clubroot development and management on canola and Brassica vegetables. Canadian Journal of Plant Pathology. 35: 175-191.

Sharma, K. , B.D. Gossen, D. Greenshields, G. Selvaraj, S. Strelkov and M.R. McDonald. (2013). Reaction of lines of the Rapid Cycling Brassica Collection and Arabidopsis thaliana to selected pathotypes of Plasmodiophora brassicae. Plant Disease. 97: 720-727.

McDonald, M.R., B.D. Gossen, C. Kora, M. Parker and G.J. Boland. (2013). Using crop canopy modification to manage plant diseases. Invited paper: European Journal of Plant Pathology. 135: 581-593.

Deora, A., B.D. Gossen and M.R. McDonald. (2012). Comparison of primary and secondary infection by Plasmodiophora brassicae in resistant and susceptible canola. Canadian Journal of Plant Pathology. 34: 239–247. DOI: 10.1080/07060661.2012.681071.

Hu, C., R. Tsao, R. Liu, J.A. Sullivan, and M.R. McDonald. (2012). Influence of cultivar and year on phytochemical and antioxidant activity of potato (Solanum tuberosum L.). Canadian Journal of Plant Science. 92: 485-493.

Saude, C., B.D. Gossen, A.W. McKeown and M.R. McDonald. (2012). Effect of Host Resistance and Fungicide Application on Clubroot in Green and Napa Cabbage. HortTechnology. 22: 311-319.

Carisse, O., M. Tremblay, M.R. McDonald, N. McRoberts, L. Brodeur. 2011. Management of Botrytis leaf blight of onion: a story of continual improvement and historical success for disease forecasting. Plant Disease. Feature Article. 95: 504-514.

Foster, A.F., C. Kora, M.R. McDonald and G.J.Boland. (2011). Development and validation of a disease forecast model for Sclerotinia rot of carrot. Canadian Journal of Plant Pathology. 33: 187-201.

McDonald, M.R. (2006). Advances in conventional methods of disease management. Canadian Journal of Plant Pathology. 28: S239-S246.

Westerveld, S.M., M.R. McDonald and A.W. McKeown. (2006). Carrot Yield, Quality, and Storability in Relation to Preplant and Residual Nitrogen on Mineral and Organic Soils. HortTechnology. 16 (2): 286-293

Kora, C., M.R. McDonald and G.J. Boland. (2005). Lateral trimming of carrot foliage for the management of sclerotinia rot of carrot. Plant Disease. 89: 549-557.

Kora, C., M.R. McDonald and G.J. Boland. (2005). Characterization of the epidemiology of Sclerotinia rot of carrot caused by Sclerotinia sclerotiorum. Canadian Journal of Plant Pathology. 27: 1-14.

McKeown, A.W., J. Warland and M.R. McDonald. (2005). Impacts of climate change on horticultural crop yields in southern Ontario. Canadian Journal Plant Science. 85: 431-438.

McDonald, M.R. and G.J. Boland. (2004). Forecasting diseases caused by Sclerotinia spp. in eastern Canada. Canadian Journal of Plant Pathology. 26: 480-488.

Westerveld, S.M., A.W. McKeown, C.D. Scott-Dupree and M.R. McDonald. (2004). Chlorophyll and nitrate meters as nitrogen monitoring tools for onions, carrots and cabbage in southern Ontario. HortTechnology. 14: 9-18.

McDonald, M.R., M.D.L.A. Jaime and M.H.Y. Hovius. (2003). Management of Diseases of Onions and Garlic. Diseases of Fruits and Vegetables: Management and Diagnosis Vol. II. 149-200.

McDonald, M.R. (2002). Vegetable Crop Pest Management (Plant Pathogens). Encyclopedia of Pest Management. 875-877.