I am having a hard time finding anything that kills this. Some people say a normal fungicide will not kill them, and I can't find products made to kill it specifically like people are saying I should do, at least products that don't cost $100. I have just learned how to prevent it, now what can I use that is safe for seedlings that will kill this stuff without harming the seedlings as well?
There is no effective, sure fire cure when damping off has affected seedlings, in fact, the seedlings usually die, so if you have a container affected in this way, get rid of the seedlings and the soil, because the soil will contain the fungal spores. Because there is no cure, most efforts regarding damping off are aimed at preventing it in the first place, especially for seeds. Damping off can occur on larger plants, but they usually manage to cope and don't get killed. See information here https://www.planetnatural.com/pest-problem-solver/plant-disease/damping-off/
You don't say whether this damping off is occurring in open ground in the soil or whether its in the potting medium you've used to raise seeds in a container. Assuming its the latter, always use new sterilised starter soil and a well scrubbed, very clean container, and don't overwater the seedlings.
My advice would be similar to Bamboo's, do not over water those seedlings. Even in 1" X 2" pots with sterilized soil you do not soak that soil, just moisten. Is there space between the seed trays and the surface beneath?
There is another critical item for a grow room; fans, ventilation! Using sterile soil will not eliminate fungal spores of damping off, nor will an enclosed room...well, maybe level 2 bio hazard (1,2,3,4) room with positive pressure.
Do not add fertilizer during this baby period. Period. Feeds fungus, baby plants use the cotyledon for chemistry until they are able to do photosynthesis on their own and then not before, those plants need basic, balanced fertilizer.
From 1"X2" seed starting trays, the next size up is 3 and 4" pots with potting soil. As your plants continue to grow in this next size up, 3 to 4" pots, you could start acclimating those starts to the out of doors garden. Takes at least 2 to 3 weeks to go through this process. Any change in environment and light source the plants need acclimatization to the new environment and light source. Just as important the reverse; taking plants indoors from green house or straight sun needs acclimatization.
Moving the air furiously will be the best prevention of damping off. Pruning excess vegetation to allow air flow. Second necessary step. Growing in a greenhouse emphasizes this air flow stuff big time. Your hair should be looking like a maniac if that fan is strong enough to minimize moisture and fungus.
Fungicide is generally considered a 'raincoat'. If not applied as a preventative, a fungicide will be useless. The exception is powdery mildew. This is the only fungus that we treat after the fact...after messing up by not having enough ventilation as well as free water on the plants.
Damping off and botrytis are in the same department. The preventative measures are major ventilation, sterilized soil and thinning of plant material. Baby seedlings don't have too much vegetation blocking the air. The spores are in the air for botrytis and damping off. Treatment
There is no cure for plants that already have damping off. However, you can easily prevent the problem by providing good air circulation. A small fan or simply cracking the lid of the germination tray will suffice. The biological fungicide Mycostop may also be used as a seed treatment to prevent seed or soil-borne diseases. Other steps for preventing damping off include the following:
When starting seeds indoors, use good organic potting soil or sterilize your own potting soil in an oven. Make sure your seed starter mix is light and fast-draining. Plant seedlings so that the soil surface is near the top of the container to insure proper air circulation. Sow seeds thinly to prevent over crowding which can lead to humid, moist conditions. Seedling trays that provide water from below are preferable to overhead watering. Never water past noon so that the soil surface and the plants are dry by evening. Avoid overwatering tender seedlings. Organocide® Plant Doctor is an earth-friendly systemic fungicide that works its way through the entire plant to combat a large number of disease problems. Apply as a soil drench or foliar spray (3-4 tsp/ gallon of water) to prevent and attack many fungal problems, including pythium, fusarium and root rot. Treatment