the black coating that follows NZ scale insects

Size
Growth: black, powdery or crust-like coating
Lifespan
1 years
Diet
Saprotrophic: grows on honeydew produced by scale insects and aphids. Does not feed on the plant itself. Grows on leaves bark and branches of trees and shrubs.
Habitat
On leaves bark and branches of trees and shrubs. Grows on honeydew produced by scale insects and aphids in native and exotic woodland areas.
Range
Throughout New Zealand in forests and gardens. Common in both North and South Islands across various elevations and forest types.
Endemism
Native
Main Threats
No significant conservation threats. Common and widespread. Not affected by habitat loss or environmental changes in forest ecosystems.
Population
Populations are considered stable and widespread. Common on trees throughout New Zealand. Not considered threatened by current environmental factors.
Conservation Status
Not Threatened
It looks like someone has dusted the plant with charcoal powder. Sooty moulds are black, powdery or crust-like fungi. They grow on the leaves and bark of trees. The black coating can cover entire leaves. It blocks sunlight. It reduces photosynthesis. The visual impact is stark. The tree appears diseased. But the fungus is not feeding on the leaf. It is feeding on honeydew. This is a sugary liquid excreted by scale insects and aphids. The insects pierce the plant's sap-carrying vessels. They drink the sugary sap. They excrete the excess as honeydew. The sooty mould grows on this residue. It uses it as a food source. The relationship is indirect. The fungus benefits from the insect's waste. On beech trees, sooty moulds are common. The honeydew is produced by a native scale insect. This same honeydew is an important food source for native birds. The kākā and tūī rely on it. In recent decades, introduced wasps have also discovered the honeydew. They compete with the birds. The ecosystem is complex. The fungus is just one part of the chain. It sits at the end of the line. It consumes what others leave behind. Sooty moulds do not harm the tree directly. They can block sunlight if growth is heavy. But the tree usually survives. The impact is cosmetic rather than fatal. In some cases, the black coating can be washed off by heavy rain. The water cleans the leaves. The fungus returns when the honeydew flows again. The cycle is persistent. The presence is constant. In New Zealand forests, sooty moulds are everywhere. Look at the leaves of any beech tree. You will see the black coating. It is a sign of a complex relationship. The tree provides the sap. The insect extracts it. The bird and wasp consume the waste. The fungus grows on the residue. Each player has a role. The fungus is the cleaner. It removes the excess. It turns waste into biomass. The forest floor benefits. The air remains clear. The balance is maintained. The name reflects the appearance. It is soot-like. It is dark. It is pervasive. The fungus does not seek attention. It simply grows where the food is. It does not care about the tree's health. It cares about the honeydew. The availability of sugar drives its spread. The insect population determines its success. The bird population influences the insect numbers. The web is tight. The connections are vital. That is the sooty mould. Black, powdery, and ubiquitous. A fungus that lives on waste. It carries on.