Mauget ArborFos 5ml, Tree Injector, Fungicide, Containing Phosphorous Acid 45.8% Completely enclosed, minimal risk application method helps avoid unwanted contamination. Environmentally Friendly. Excellent compliment to a total plant health care program. ArborFos is a patented formulation that is university and field tested. Phosphite formulated fungicide that inhibits fungal growth through stimulation of the plant's own natural defense systems.