Oak Tree Honeydew and Sooty Mold: Aphid Control via Soil-Applied Insecticide

A homeowner describes a large oak with shiny sticky leaves, green "lice" (aphids) underneath, and black sticky droplets coating fences, walls, and cars. They ask if the "lice" cause the black fallout and want a root-applied insecticide safe for kids, chickens, and dogs.

Expert Answer: The "lice" are aphids. They secrete honeydew (sugar-rich), on which sooty mold grows, turning surfaces black. Controlling aphids stops honeydew and mold. Use Bayer Advanced Tree & Shrub Insect Control applied to soil around the tree; roots transport it to leaves. It takes weeks to reach canopy, lasts all season, and is safe for pets/kids once dry. Apply in spring. Product link: Bayer Advanced.

Follow-up: Honeydew doesn't cause allergies/infections, but airborne sooty mold spores might. Controlling aphids eliminates the mold.