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Researcher requesting garlic samples

June 15, 2016  By OMAFRA

Garlic bulb infested with stem and bulb nematodes OMAFRA

June 15, 2016, Guelph, Ont – Several fields of garlic in Ontario have been completely destroyed by stem and bulb nematodes in recent years. This microscopic worm-like pest has been spreading from field to field unknowingly in contaminated garlic cloves sold and used for seed.

Obvious symptoms of stem and bulb nematode damage often do not appear until late June or early July when the scape has emerged. Infected plants appear stunted, turn yellow, dry prematurely and are easily pulled from the soil leaving the rotted region of the bulb where the roots attach, called the basal plate, in the soil. Infested garlic bulbs tend to be soft, shriveled, discoloured and lighter in weight. Often bacteria, fungi, maggots and mites will invade severely infested bulbs causing them to become mushy with soft rot and decay.

There are many strains of stem and bulb nematode. Some strains can infect a few hosts while others have a broad host range. Based on research results conducted at the University of Manitoba, the Ontario garlic strain can infect and reproduce on yellow pea, bean, chickpea, and garlic but not on lentil, spring wheat or canola. Common crops grown in rotation with garlic in Ontario were not tested and will be the focus of two research projects over the next couple of years by University of Guelph and Agriculture and Agri-Food Canada in St-Jean-sur-Richelieu, Québec. Another objective of research is to evaluate the genetic diversity of the stem and bulb nematode populations in Ontario and Quebec and eventually link that information to host range.


In order to learn about the diversity of the stem and bulb nematode populations in Ontario garlic, Dr. Benjamin Mimee, AAFC, is looking for two to three bulbs of garlic infested with stem and bulb nematode from 15 to 20 different locations across Ontario. If you have stem and bulb nematode damage in your garlic, please call Michael Celetti at 519-824-4120, ext. 58910 to arrange for a sample of the infested garlic to be picked up. Alternatively you can send your stem and bulb nematode infested garlic bulbs to:

Michael Celetti,
Plant Pathologist – Horticulture Crops Program Lead, OMAFRA
Room 3110, Edmund Bovey Building, University of Guelph,
50 Stone Road, Guelph, Ontario
N1G 2W1

The infested bulbs should be placed in a paper bag or wrapped in newspaper. Your name, address and phone number as well as the variety should be printed on the bag or on a separate piece of paper included with the sample in order for us to contact you if we require further information about the sample.

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