When I see a germinated seed in one of my petri dishes, I normally give it a quick dip in drugstore type 3 % hydrogen peroxide then plant it root down in my planting media.
This spring I was getting an excess of germinations from rugosa hybrids so I decided to do a little experimenting. I took some Antistress 2000 from a ready to spray commercial spray bottle and place it in a wide mouth bottle that I could cap between use.
At first I tried the following on just 1 seedling. I submerged the germinated seedling in the Antistress solution and then planted in my normal way. Low and behold it survived and grew!
I have since tried it on 2 more seedlings and they also have survived and have grown into small plants.
If you try this, please let us know as we may have an alternate method to prevent damping off and/or whatever is causing some of the young seedlings to die.