Ran into some damping off problems again recently. Even though I clean my tray well between uses I decided to run it through the dishwasher this time. Did that and it was no help. I've lost 2 of my 10 seedlings for my outdoor plants. Did a little research and found that mixture of 1 tablespoon of 3% hydrogen peroxide to 1 quart of water, sprayed on the seedlings, will kill the bacteria and/or fungus that cause damping off. I've been doing that for 2 days now and 2 other seedlings that I thought I might lose have recovered nicely. Seems to be a very effective resolution to this problem.