Green Cucumber seedling on tray close up

SAVE THE SEEDLINGS — Damping off is a rotting of stem and root tissues at and below the soil surface, and the mushy stem will cause the seedling to fall over at the base and die.

In seed-starting presentations, I always caution folks to be aware of damping-off, a disease that can devastate seedlings.

I’d not personally seen this problem in more than 35 years of starting seeds indoors, but last winter damping-off hit my greenhouse with a vengeance. Here are some things to watch for and how to get your seedlings back to growing normally if this disease appears.

Damping-off can be caused by any one of several fungi in the seed starting medium (Rhizoctonia, Pythium, Fusarium, Phytophthora, Sclerotinia, Sclerotium, or Botrytis). Symptoms may include poor germination, stems rotting at the soil line, stunted seedlings and/or a moldy fungal growth.

Using a sterile peat-based seed-starting mix is probably the best way to avoid damping-off. Providing drier conditions by increasing the ambient temperature and air flow, and being careful to not overwater, also can help. Rinsing any containers re-used from last year with a bleach solution will prevent any previous infection from recurring.

When the disease strikes, a number of different fungicides can be used for control. The manufacturer’s label might not specifically mention damping-off, but may list one or more of the individual fungi above that cause it.

But be aware that some of these fungicides also may cause stunting and yellowing of young seedlings, so read the label carefully before using.

In my case, I used an organic fungicide. I sprayed the seedlings thoroughly, repeating the treatment as recommended on the label. An improvement in growth for many of the seedlings was noticeable within a few days.

But poor seed germination and seedling stem rot had taken their toll, so I had to (Oh no!) buy some replacement plants locally. The seedlings that did survive needed more time in the greenhouse before setting outside. But they were fine all summer.

Jim Janke is an Extension Master Gardener Volunteer in Haywood County. For more information, visit haywood.ces.ncsu.edu or call the Haywood County Extension Center at 828-456-3575.

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