What can the excretion of honeydew from sap feeders lead to?

The excretion of honeydew from sap feeders, such as aphids or scales, can lead to mildew formation. This is because honeydew is a sugary substance that provides a perfect nutrient source for fungi, particularly the sooty mold that can develop on surfaces where honeydew accumulates. When this sticky substance falls onto leaves, it can attract mold spores, promoting fungal growth. The presence of this mold can interfere with photosynthesis by blocking light from reaching the plant's leaves, ultimately resulting in negative impacts on plant health.

While beneficial insect attraction can occur because honeydew can attract certain insects like ants or even some predatory insects that feed on aphids, the primary ecological consequence of honeydew excretion is the potential for mildew formation, making it the most relevant concern in this context. Improved plant growth is not a typical outcome of honeydew excretion, as the associated mold can damage the plant. Leaf discoloration can stem from various issues, but it is more a symptom of the problems caused by mildew rather than a direct result of honeydew itself.