Aloe Vera, willow bark, and honey all contain salicylic acid which acts as a fungicidal agent and helps to stimulate root growth. All are loaded with lots of enzymes and amino acids as well which also help to stimulate root growth.
I've used both aloe and honey with good results. I've never used willow bark but the results should be similar.
Willow bark works especially well when germinating & on young seedlings. Years ago we'd put an aspirin tablet or two in the dirt around each plant for the salicylic acid.