Melanose: identify, prevent, control

Updated October 2026

Worst in warm, wet springs and summers on the coast of Queensland and New South Wales, when new leaves and young fruit are developing.

Melanose is a fungal disease of citrus that marks the skin of fruit and leaves with small, raised, dark brown specks. The fungus lives on dead twigs in the canopy and is splashed onto young growth by rain, so old, untidy trees with plenty of deadwood suffer most. It is mostly a cosmetic problem, because the flesh inside is fine, but heavy infection can stunt leaves and make fruit look very rough.

Diaporthe citri

How to identify it

• Run your hand over affected leaves or fruit and they feel rough, like fine sandpaper, because the specks are raised above the surface.
• The specks start as tiny brown dots about a week after infection and become reddish brown to almost black as they fill with gum.
• On fruit the spots often form streaks or tear-stain patterns where rain water ran down the skin, and heavy infection joins them into a cracked crust often called mudcake.
• Young leaves can be dotted all over and may be slightly distorted, while older leaves keep the rough specks for the rest of their life.
• Look inside the canopy for thin dead twigs; plenty of deadwood plus spotted fruit is a strong sign that melanose is the cause.

What it is often confused with

When and where it is worst

Melanose is a disease of humid, rainy districts, so it is most common in coastal orchards and backyards from Far North Queensland through South East Queensland to the NSW coast. It is far less of a problem in the dry inland and in Mediterranean-climate gardens around Adelaide and Perth. All citrus can be infected, including lemons, limes, mandarins, oranges, grapefruit, cumquats, tangelos, blood oranges, pomelos and finger limes, with grapefruit among the most susceptible.

Spores form on recently dead twigs during wet weather and are carried a short way by rain splash. Infection needs a long period of wet leaves, around 10 to 12 hours at 24 to 27°C and longer in cooler weather. New leaves and young fruit are at risk from petal fall in spring until the fruit is a few centimetres across, usually late spring into early summer, after which the skin becomes resistant.

Plants it affects

These plants in our library list it as a problem to watch for.

How to prevent it

• Prune out dead twigs and branches every year, ideally in late winter before the spring flush, because deadwood is where all the spores come from.
• Open up dense trees so leaves and fruit dry quickly after rain.
• Remove prunings and fallen dead wood from under the tree rather than leaving a pile nearby.
• Keep trees healthy with steady watering and feeding so they carry fewer dead twigs, and act quickly on frost, drought or borer damage that kills wood.
• Avoid overhead sprinklers that wet the canopy for hours.

Organic control, step by step

• Start with sanitation: remove deadwood and old spotted twigs before flowering, which on its own often keeps melanose to an acceptable level in backyard trees.
• If your fruit has been badly marked in past seasons, apply a copper spray at petal fall to protect the young fruit.
• Repeat the copper about four to six weeks later while the fruit is still small, and again if the weather stays wet.
• Use copper in mild weather and do not mix it with oil, because copper applied in hot conditions can mark fruit.

Conventional control

• Copper fungicides (copper hydroxide or copper oxychloride) are the standard home garden option for melanose on citrus, applied at petal fall and again a few weeks later.
• Mancozeb is registered for some citrus diseases in home garden products; only use it if the label lists melanose on citrus.
• Read the label, check citrus and melanose are listed and keep to the withholding period before you pick fruit.

Frequently asked questions

Related problems

Sources: NSW DPI, Melanose (Primefact 751); UF/IFAS EDIS, Florida Citrus Production Guide: Melanose. Identification and control follow these sources. Always read the product label before use.