There are cottony white masses on my tree's branches. What are they?

Fluffy, cottony white masses on twigs and branches are usually the protective wax of sap-feeding insects — most often woolly aphids, cottony cushion scale, or mealybugs. The white "cotton" is a waxy secretion that shields the soft-bodied insects underneath.

How to tell them apart:

• Woolly aphids: Cottony tufts that may seem to "fly" (winged forms); often on alder, apple, beech, elm. Produce honeydew.
• Cottony scale (e.g., cottony maple scale): White cottony egg sacs attached to twigs, with the scale insect at one end. Common on maples and other hardwoods.
• Mealybugs: Slow-moving, segmented insects with a cottony coating, more common on shrubs and houseplants.

Are they harmful?

Light infestations are mostly cosmetic. Heavy populations cause: - Sticky honeydew that drips onto cars and decks - Black sooty mold growing on the honeydew - Yellowing leaves and reduced vigor on already-stressed trees

Control:

1. Strong water spray knocks many off accessible branches.
2. Horticultural oil (dormant or summer rate) smothers eggs and crawlers — timing for the crawler stage is key.
3. Encourage natural predators — lady beetles and lacewings devour these pests.
4. Heavy scale infestations may warrant a systemic insecticide; consult a certified arborist.