Ma Nature keeps disease under control better outside with natural ultraviolet light, wind. I never sterilize anything that I wintersow. Heck, nothing is even clean.
Inside, with no wind, no sunshine, cold wet soil, conditions can be perfect for bacterial and fungus growth. That's why good lights, heat mats, fans, chemicals, sterile soil and seeds, give seeds a better chance indoors.
Years ago, (OK, decades ago) when I knew nothing about seed starting, my attempts always ended in damp off. Once I got serious and learned a few things, I've never had it at all. I usually cook the potting mix, use bleach on pots and trays, use t5 lights and heat mats and fans... and never have damp off. Though after gardening in this yard for 35 years, I have more plants than I can handle, so I really don't start many seeds anymore.
How to wintersow:
https://garden.org/ideas/view/...
We also have a wintersowing forum
https://garden.org/forums/view...
Karen
