I start a lot of petunias indoors and in past years I have boughten "Damp-Off" concentrate and used it in a spray bottle to mist the soil/seedlings. Damp-Off is no longer available in Canada, so I am looking at some different options and also less "chemical"
Of course overwatering & cool temps is part of the cause, running a fan helps, overcrowded seedlings is also a problem. Sterilizing the soil in the microwave may help.
Here's what Google Search came up with. What do you recommend?
Chamomile Tea: Naturally high in sulphur, this popular tea is a fungicide. Make an infusion with three chamomile teabags and allow it to steep for about 20 minutes. Add the concentration to a sterilized spray bottle and mist the seedlings once they start to sprout.
Ground Cinnamon: A natural anti-fungal, sprinkling the soil surface with some ground cinnamon can stop damping off. This needs to be done only once.
Hydrogen peroxide: Add one cup of hydrogen peroxide to one gallon of boiled water. Allow it to cool and mist the seedlings.
Organic gardeners have reported success using sprays created with seaweed extracts or diluted Neem oil.
In my experience, the only good treatment for damping off is maintaining correct growing conditions with sterile media. (as you stated) Many people cite anecdotal evidence of various things working for them, but I am sceptical in the absence of any real side by side comparisons in replicated trials. People who state "I use (insert favorite treatment here) and I never have any problems with damping off" have proven nothing except they never have damping off. If you don't have side by side comparisons with untreated plants, that then become infected and die while the treated plants are thriving, you have proven nothing. It my science background and training speaking here, I am not trying to offend any of those or their favorite treatment.
Having said that, it is prevention of damping off, not treatment that we are primarily concerned with. Once an individual plant has been infected, there is no treatment on earth that will save it. There are no currative treatments available. As prevention is key, it doesn't make sense to me to be misting plants with any chemical mixed with water. No matter how effective the chemical is, you will still be adding humidity to the environment which only increases the chance of further infection.
Personally, I don't use anything for damping off. I am very careful with sterilization of pots/trays and any surface coming in contact with my planting media or seed. I also will err on the side of dry when germinating plants that are susceptible to damping off.
I have read some research that found cinnamon to be a good "home remedy" treatment in preventing damping off. I don't recall the sources, or the exact treatment protocol, but I would imagine there is a lot of forgiveness in the amount to use (I can't image cinnamon being phytotoxic). I would not use any treatment that used water as the carrier and added humidity to the equation.
Finally, remember the disease triangle. For plant disease to occur you need three things, a pathogen, a susceptible host, and environmental conditions favorable for infection. Take away any of those three and you have prevented the disease. So assuming we aren't going to elimate the host (LOL), we can eliminate the pathogen through sterilization, the favorable conditions through proper humidity/temperature management, and prevent a susceptible host with chemicals (including conventional fungicides and other treatments).
I hope some of this helps your search for a new treatment, I am sure that based on other threads, this topic will have dozens of replies and probably generate a good deal of discussion.
I used to have some problems with damping off with seeds germinating in the house or overwatering in the greenhouse. That's all history since several years ago I started using hydrogen peroxide. I add 1/4 C to a gallon jug of water. I use it for soaking seeds and watering until they get a couple sets of true leaves. I also use plain unsterilized potting soil and it works like a charm for starting seeds and growing.
Hydrogen peroxide has some antiseptic quality that kills pathogens and also carries lots of oxygen to the roots. It's practically impossible to drown something if you have drainage holes in your container. Everything loves it.
I use a commercial soil-less seed starting mix - not potting soil - like "Jiffy". I sprinkle a bit of dried crumbled Sphagnum moss (not peat moss) on the surface. I read this tip a long time ago, I don't remember where - I guess most bog plants have naturally occurring fungicidal properties. Once the seeds sprout, I try to change from top watering to bottom watering. I haven't had a problem with damping off, but perhaps I don't have that particular fungus spore around. I would assume it would be more of a problem in the future if you have had problems - and spores - in the past.
As trc65 said it really comes down to cultural conditions. I grow my seedlings as dry as I can without killing them- and keeping them as cool as the species will allow helps too. Having a fan set to come on periodically will help too. I rarely if ever sterilize anything anymore- as soon as you kill everything off it comes right back- it's everywhere. And I'm lazy! I haven't had anything damp off for the longest time. Maybe just luck I guess but really I think keeping everything as dry as possible is the key.
As a weekend gardener, I usually find daily conditions impossible to control. Damping off vs drying out has been the constant dilemma in choosing what to do when I leave for the week. Heat mats early on and capillary matting are necessities, I think, but covers are another matter...Last year I was overly worried about the cold house and used frost blankets over the whole thing. Spring was unusually warm...disaster!
This year I'm starting some seeds early on a NY windowsill, and just saw the first signs of fuzz. Yikes! I got the covers off fast enough, but have been searching around for remedies. I've decided to try the cinnamon method on snaps, tomatoes, and Nic Avalon, covers on, hoping it will solve the problem once I get going full steam in CT.
Joanna gave me the idea for using chamomile tea.
It has something which discourages mold, but it does not seem effective against algae.
I also keep a spritz bottle of dilute peroxide and if mold shows up---
it gets a spritz of the peroxide.
If your home is dry-----then perhaps keeping a tray or basin of water
near your seedings would improve the humidity.
I also keep a pan of water on the stove just so it evaporates and makes the house more humid.
When it is cold here the air gets very dry!
I haven't had problems with damping off. Looking back over these posts, I think maybe the reason is my water is very alkaline and my air is very dry. I had some old seed that never sprouted, those trays did mold after I had discarded them. I might try the cinnamon anyway - when I was cleaning the spice cabinet, I noticed I had extra.
I have some hydrogen peroxide that came as a spray. Would it be too strong and need diluted?