Tips on Tree Nursery Practices IV: Media Biology
Mold like mushroom is almost always non-pathogenic. This mold often goes away after planting. However, one mold can harm the crop by preventing water from penetrating into the mix.
This is a slime mold (Ostracoderma sp) that has a gray threadlike structure (mycelium) that repels water. It grows quickly and causes the media to remain dry even with repeated irrigations. This is very common in outside nursery containers.
A bark or sawdust or coconut coir that has been adequately composted will suppress some root or crown rots. During composting, beneficial microorganisms colonize on the media mix.
The beneficial microorganisms compete with the disease organisms and once the beneficials are in place, the pathogens have no place to live.
This is because the composting process causes rapid heating which destroys most fungal and bacterial organisms. As the compost cools, new organisms (vast majority being beneficial to plants) rush to repopulate the media.
UPV Centennial Forest 