Our pool deck suddenly developed rust color stains. We can remove the stains with a scrub brush and a mild cleaner, but the stains always return within a day or two. We have a Eucalyptus tree close by. Could this be the cause? We never see any foreign matter from the tree on the deck (no leaves, sap, etc). But the stains are definitely there. It's a mystery!
Stains on Pool Deck From Tree
Certified GKH Gardening Expert
The tree may have a pest problem and the pests are secreting honeydew. It would be almost the consistency of water. Honeydew, though, attracts fungus, so what you may be seeing is a fungus growing on the deck because of honeydew. Check the tree carefully for pests. They will most likely be under leaves or in the crotch area of branches.