Melanose: identify, prevent, control

Updated October 2026

Infects young fruit and leaves in rainy weather from spring flush to early summer, mainly in Florida, the Gulf Coast, South Texas and Hawaii.

Melanose is a fungal disease of citrus that marks the rind and leaves with small, hard, dark specks. It rarely harms the tree or the eating quality of the fruit, but heavily marked fruit looks rough and unattractive. The fungus grows on dead twigs inside the canopy, so trees with plenty of dead wood after a freeze or years without pruning get it worst.

Diaporthe citri

How to identify it

• Tiny, raised, reddish-brown to black specks appear on the rind of young fruit, and they feel rough, like sandpaper, when you run a finger over them.
• Where rain or dew has run down the fruit, the specks form streaks or drip-shaped patterns, which growers call tear-stain melanose.
• Heavy infections fuse into larger, cracked, crusty patches called mudcake melanose, which can make young fruit misshapen.
• Leaves show small, raised, dark brown specks, sometimes with a faint yellow halo, and the leaf surface feels rough.
• Young green twigs can show the same raised specks, and you will usually find small dead twigs nearby in the canopy.
• The specks stay on the surface of the rind and the flesh inside is normal.

What it is often confused with

When and where it is worst

Melanose is a problem wherever citrus grows in a warm, rainy climate. It is common in Florida, along the Gulf Coast in Louisiana and South Texas, and in Hawaii, and it is much less of a concern in the dry citrus areas of California and Arizona. Grapefruit is the most susceptible, but oranges, mandarins, tangelos, lemons, limes, kumquats and pomelos can all be marked.

Spores are made in small dead twigs, especially ones that died within the last few months, and are splashed onto young tissue by rain. Infection needs about 10 to 12 hours of wetness at 75 to 80°F, or longer in cooler weather. New leaves are susceptible until they harden off, and fruit stays susceptible from petal fall until it is roughly 2 to 3 inches across, which in Florida means April to early July. Freezes that kill twigs often lead to bad melanose the following spring.

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 from inside the canopy every year, ideally in late winter before the spring flush.
• After a freeze, remove the dead wood once new growth shows where live wood begins, before the rainy season starts.
• Take prunings away from the tree or dispose of them promptly rather than leaving brush piles nearby.
• Keep trees healthy with regular feeding and watering so they carry less dead wood.
• Thin crowded branches so the canopy dries faster after rain and dew.

Organic control, step by step

• Start with pruning out dead wood, which removes the source of spores and is often all a home tree needs.
• If fruit appearance matters to you, apply a fixed copper product labeled for citrus and allowed in organic growing about two weeks after petal fall.
• Repeat the copper spray about every three weeks through the rainy period until fruit is about 2 to 3 inches across, more often for grapefruit.
• Spray in the cooler part of the day and avoid spraying copper in hot, dry weather, which can mark the fruit with star melanose.

Conventional control

• Fixed copper products, such as copper hydroxide or copper octanoate, are the main home garden fungicides for melanose on citrus.
• Other fungicides used by commercial groves are not generally sold in home garden packs, so pruning plus copper is the practical home program.
• Read the label, check that citrus is listed, and keep to the pre-harvest interval.

Frequently asked questions

Related problems

Sources: UF/IFAS Florida Citrus Production Guide, Melanose (CG019); UF/IFAS Extension, Citrus identification guide: fungal diseases; UF/IFAS Citrus Research and Education Center, Foliar fungal disease management (2022). Identification and control follow these sources. Always read and follow the product label.