The Honeydew Mystery

Sap-sucking insects like aphids produce a sticky substance called honeydew—a common seasonal occurrence that reflects their population levels. This sugary secretion typically appears during the growing season and increases as aphid and related insect populations, such as certain scales and whiteflies, rise. While we can’t directly control these insect populations, factors like weather, plant health, and pest control practices influence how often honeydew appears. When it accumulates, honeydew often triggers the growth of sooty mold—a black fungus that feeds on the sugar and harms plant health. Each year, the frequency of honeydew in any area closely tracks with the local populations of aphids and similar pests.

Honeydew dripping onto the road indicates a high population of sap-sucking insects nearby. The volume of liquid shows that many insects are actively feeding on plant sap. Aphids produce most of the honeydew, though other insects—such as whiteflies and certain scale species—also contribute. While many insects consume honeydew as a food source, aphids and whiteflies are the most well-known producers.

This kind of accumulation—especially when paired with sooty mold—poses a threat to tree health. By blocking sunlight and interfering with photosynthesis, it can reduce both the tree’s immediate vitality and its long-term chances of survival.