Damping-off is a common disease that kills seedlings in the greenhouse. Damping-off can kill both germinating seeds and young seedlings. Several fungi can cause this disease, including Rhizoctonia solani, Pythium spp., Phytophthora spp., Sclerotinia spp., and Botrytis spp. Practically all species of plants can be affected.
Pre-emergence damping-off is a term used to describe the rot of seeds, or the death of the seedlings, before they emerge from the soil. Post-emergence damping-off affects seedlings that have already emerged from the soil. These seedlings may develop a dark stem rot near the soil surface which will cause them to fall over and die as the rotted area shrivels.
I left early Saturday morning for a flight to Chicago. At 5:30am, right before I left for the airport, I removed the dome covering the tray, watered the seedlings, replaced the dome and did not give them any more thought until I returned the following Tuesday. It turns out I forgot to re-open the air vents on the dome before I left. The poor guys were suffocating the entire weekend. The still air and wet conditions made a perfect environment for the fungi to grow.
So far I've lost 2 Fairy Tale eggplant seedlings, 2 King Crimson pepper seedlings and 5 Atris pepper seedlings. They were discarded as soon as I realized what happened. There are a few seedlings I'm not sure are affected so I'll be watching them for the next few days. I would have had a 100% germination rate if weren't for this :(
I drained excess water from the tray and re-opened the vents on the dome. At first I removed the dome entirely, but I put it back on a few hours later when I decided it was still too cold on the windowsill to go without it. I'm going to sow more seeds in a separate tray. I have plenty of Fairy Tale and King Crimson seeds, but I'm out of Atris seeds. Sorry everyone, I don't think I'll be able to give away any Atris pepper seedlings like I planned.
Never garden when you're half asleep, it can lead to stupid mistakes!