Pests and Diseases: Damping Off


Picture courtesy of UConn

With all of the talk about starting seeds for your veggie garden, I thought that it would be appropriate to look at a disease known as “damping off” that can affect your seedlings. Damping off is a catch all term that is used to describe what happens to seedlings when they essentially rot right at the soil line and fall over. Damping off can also occur before the seedling emerges from the soil, but the most common form of damping off is when the seedlings’ stems turn black at the soil line and fall over. It can be caused by many soil-borne fungi including Pythium, Sclerotinia, Phytophthora, Rhizoctonia and Botrytis. Needless to say, damping off is fatal to the young seedlings.


Perhaps the easiest way to prevent damping off is to use clean potting soil when starting your seeds indoors. I’m a huge fan of compost but I generally start with a pre-packaged sterile potting soil. Once the plants make it past the seedling stage, they aren’t susceptible to damping off so it’s OK to topdress them with compost then.

Another key preventive measure is to keep the seedlings dry. That doesn’t mean that you can’t water them…it just means that you should only water them when they need it. I have found through the years that gardeners tend to love their plants to death…the usual means of killing them is through overwatering. With seedlings, it is especially helpful if you water them from the bottom. Fill the tray with water and allow the plugs to absorb the water for a few minutes. After a few minutes, dump the excess water out so that your plants don’t drown. Many seed starting kits come with a little plastic dome that you can use to create a little miniature greenhouse effect. I have found that it is best to either leave the domes off or at least prop them up…otherwise the potting mix tends to stay too wet and that invites damping off.

Getting the plants growing vigorously can also prevent damping off. If you don’t have a greenhouse, place your grow lights as close to the seedlings as possible to get them up and growing. When I say close, I mean close…1″-2″ from the tallest seedlings is perfect. Otherwise, the seedlings become tall and lanky and literally grow themselves to death. They use up all of the energy that is stored in the seed trying to get tall enough to reach the light. That’s a pretty pitiful way to die if you ask me. Don’t fertilize them until they are larger…otherwise they’ll grow too fast for their roots to keep up with.

Air circulation is key to preventing damping off too. That’s another reason that I don’t like those little greenhouse domes. If you are starting your seeds in your house (as I do) then the normal amount of air circulating from your heating system should work just fine. Otherwise, set up a little oscillating fan several feet from your seedlings…just be sure to keep a close eye on your seedlings as they are more prone to dry out this way.

Use clean, sterilized containers when starting your seedlings. In the past I have used the Jiffy pellets but they are pretty expensive. This year, I’m hopeful that I can purchase a Soil Cube. It’s a great value for the price and once I have it, I won’t have to buy those little pellets ever again. Either way, I’ll still have to put the the pellets or soil cubes in something, so it is imperative that it be clean. I re-use my plastic flats year after year and they are stored outside during the summer months. All I do is knock the debris out and soak them in a bleach solution in my kitchen sink. I guess I should measure how much bleach I use, but I don’t. I just pour a good amount of bleach into the sink and add water to cover the flats. I usually let them soak for 5 or 10 minutes (or longer if I get distracted) and then rinse them with clean water. They are then ready to use.


Unfortunately, all that you can do is pitch them. I know that seems devastating but hopefully you can eliminate the pathogen before it decimates the rest of your seedlings. If you are growing your seedlings in flats, it is best to pitch the infected ones and move the remaining seedlings to another sterilized flat. If any of the soil from the infected seedlings is touching its neighbors, it would be prudent to pitch the neighbors as well. Better safe than sorry!

I hope that you have gleaned some helpful information from today’s post. The most important thing to remember is that there are setbacks that can happen in any endeavor. Don’t be discouraged if you have problems with damping off. Professional growers experience this same disease but yet they keep on growing plants. Just eliminate the infected plants and sow some more seeds to replace the ones you lost. You will be rewarded time and time again when you are harvesting the fruits of all your labor this summer. Let me know if you have had any problems with damping off. Leave me a comment below or e-mail me at Happy gardening!


December 27, 2011Permalink Leave a comment

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