The Best Cure is Prevention: Stay Nematode Free

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Stem and Bloat Nematode:  The Garlic Farmer’s Worst Nightmare

The dreaded Stem and Bloat Nematode–this is something you don’t want taking up residence on your farm or in your garden.  Nematodes are microscopic round worms and feed inside the leaves, stems and bulbs of garlic and other members of the allium family.  Once introduced to the soil, they reproduce rapidly and can destroy an entire crop.  The real danger, however, is the nematode’s ability to withstand harsh conditions and survive FOR YEARS in infected plant debris or soil.  It’s spread through infected seeds and can be transferred from one end of the farm to another by contaminated garden equipment.

Signs of a Nematode Infestation

Symptoms of a nematode infection in garlic plants include stunted growth, yellowing of leaves and bulbs which turn dark brown and become soft and shrunken.  Seriously, this can wipe out your entire crop in a single growing season.  Unfortunately, it’s possible to have infected seed garlic that shows no symptoms, but harbors the parasite.  Once soil is infected, this pest is notoriously difficult to get rid of.

Don’t Be Afraid to Ask

The solution is to prevent the introduction of the nematode entirely.  Whether you purchase seed garlic from Natural Jack or another grower, always insist on seed that is nematode-free.  Serious growers of seed garlic regularly test for nematode and will offer an assurance that their product is clean.  Natural Jack’s seed garlic and soil are tested annually. You can see our test report from soil samples this summer here. We aren’t taking any chances.  You shouldn’t either.  If you want more than just our word for it, ask to see our most recent soil test report.  We’ll gladly share our results so you can be confident Natural Jack’s garlic is nematode-free.

Be Proactive

If you are concerned about your own soil or seed, contact your local cooperative extension office. They can direct you to a reputable lab for testing in your region.  The best time to test your soil is August through October when nematode populations are at their highest level. It’s better to test than guess!

Other recommendations to prevent this nasty pest include crop rotation and planting certain cover crops.  Mustard, rapeseed, and sorghum-sudangrass release compounds that are toxic to nematodes when tilled into the soil.

The bloat nematode strikes fear in the heart of the garlic farmer–as it should.  Purchase only seed that is tested nematode-free.  You’ll sleep better at night.



nematode infected garlic and healthy garlic
Garlic damaged by the stem and bulb (bloat) nematode (Ditylenchus dipsaci) on the left and a healthy bulb on the right. Photo by Christy Hoepting.