What Are These Black Spots On My Phalaenopsis Orchid Leaves?

Black Spots Orchid

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Black Spots On My Phalaenopsis Orchid Leaves

Phalaenopsis and other orchids respond quickly to any problems in their environment. Pimples are one of the signs of trouble. The first step in treating dark spots on orchid leaves is diagnosing the problem.

Some phalaenopsis have naturally speckled leaves, so it can be a natural coloring. However, staining the leaves can also signify a bacterial or fungal disease.

Bacterial leaf spot is quite common among orchids and can be aggressive and dangerous to phalaenopsis. They also cause fungal ailments and leaf spots, especially if the plant is left exposed to moisture on cold nights.

Unless the plant is valuable, the best approach is to dispose of it, as the disease is highly contagious and will spread from plant to plant due to splashing water.

Black Rot

A hazard to orchids when the weather is rainy or humid for prolonged periods, black rot can quickly destroy an entire plant if left unchecked. Caused by one or both Pythium ultimum and Phytophthora cactorum fungi, black rot affects a wide variety of orchids.

A Fungal Infection

The fungi that cause black rot in orchids consist of independently moving spores, called zoospores, that swim in the water. If that water is found on an orchid leaf, the zoospores can penetrate the plant's tissue and begin the next stage of its life cycle.

Once this occurs, the visible signs of infection (small watery, translucent spots) quickly expand and turn brown and then black. If left untreated, the affected plant or plants can infect others and are likely to die on their own.


As the name suggests, black rot looks like dark blackish spots or lesions on the affected part of the plant. The black spot or spots grow quickly and can spread throughout the plant.

If allowed to reach the crown of a monopodial (single stem) orchid, the rot will kill the plant. Affected leaves may turn yellow around the infected area, and the lesions themselves will be soft and ooze water when pressure is applied.


Unsterilized flower pots, soils, or sources of water, as well as water sprayed from nearby affected plants, are excellent means of spreading the fungus.

If your orchids are outside, keep them 3-4 feet above the ground to avoid contamination from splashes. Both on the outside and inside, don't let the orchid leaves stay wet for long periods of time.

Good air circulation in the growing area is essential. At the first signs of infection, separate all affected plants to avoid contaminating healthy plants. Finally, some growers recommend using a high calcium fertilizer in spring to avoid black rot on new shoots.

Cut out the Rot

To stop the spread of black rot in your orchid, start with a sterilized knife and cut off the diseased part of the plant. Remove the infected part of the leaf, or the entire leaf if necessary, to stop the spread of the fungus before it reaches the crown.

Place the plant in an area that receives good air circulation to allow the cutting to dry.

Black Spots Orchid

Use a Fungicide

Once the infected plant parts are removed, a fungicide should be applied to protect the remaining healthy tissue. Cinnamon is an excellent fungicide and ground cinnamon can be applied directly from the spice jar directly to the exposed area where the infected parts of the plant have been removed.

First Rays Orchids also recommends mixing cinnamon with a casein-based glue (such as Elmer's) or cooking oil to form a thick paste. This paste is quite waterproof and can be used to cover the wound.

Another option is to soak the affected plant with a fungicide. If the disease is diagnosed early, the use of a protective fungicide such as Truban or Terrazole is recommended.

For more advanced cases, a systemic fungicide such as Aliette or Subdue is more effective. Some growers have also recommended Captan, Dithane M-45, BanRot, Subdue, and Physan 20 for black rot control.

Enjoy This Video Tutorial About What are black spots on Orchid leaves?

Source: MissOrchidGirl

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Black Spots Orchid

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