Black Spots on Orchid Leaves: 6 Causes & Solution

Black spots in Orchids
Black spots in Orchids may develop due to overwatering, improper lighting and fungal infections.

My Orchid Cymbidium was doing fine until this spring, when it started displaying black spots, which looked suspicious!

I knew the bright direct light did not cause it because it was always kept under indirect sunlight.

Hence, it did not take much time to figure out that my beloved plant was under severe duress.

Black Spots on Orchid leaves are usually byproducts of bacterial and fungal infection caused by Acidovorax (syn. Pseudomonas), fungi Pythium ultimum, or Phytophthora cactorum, leaf spot; while other times, change in environment may also cause blackening foliage.

Beautiful Orchid
Provide your Orchid plant an ideal environment to grow.

You could tell it by seeing the black or brown spots, smudges, or darkening foliage, but not all problems exhibit the same signs.

Read on to learn more about the causative agents of black spots in the Orchid plant and how to treat them.

Can Excess Black Spots on Leaves Kill Orchid?

The unusual black or dark spots on Orchid leaves and smudges may indicate the onset of a big problem because that is unlike the appearance of Orchids.

Orchid comes from rainforests with a tropical to temperate environment and boasts about 28,000 species worldwide.

Orchids have been associated with virility and fertility since 500 BC, primarily the Cymbidium Orchid, known for its waxy green leaves and sweet-smelling flowers that signify luxury and strength.

Remember, black patches on cymbidium Orchid leaves indicate black rot, which will increase and may even kill the plant if left untreated.

Bacterial and fungal infection is usual with improper lighting, overwatering, low humidity, pest problems, and compromised plant health.

Black spots in Orchid
Black spots in Orchid leaves may appear due to overwatering, improper lighting, pest, and disease infestation.

Although some amount of round black spots on Orchid leaves are not considered dangerous, excessive dark proliferation means your plant is dying from root rot.

Overly blackened leaves cannot be revived, but you can restore the plant’s appearance with appropriate remedial measures.

It will snatch the vital energy and nutrients that would otherwise help boost greener leaves and a healthy appearance.

The best way to prevent black spots is to keep your Orchid healthy!

How to Identify Black Spots on Orchid?

It may be easier to figure out black spots on Orchids as the vivid looking leaves quickly lose their vigor.

It may be expected in late spring or summer when the plant actively grows, attracting different problems.

Here are the tell-tale signs of black spots on Orchids and their causative agents.

  • The Orchids suffering from root rot will exhibit leaves that may turn yellow around the infected area and feel soft to the touch, especially spots caused by fungus and bacteria.
  • When pressed, the infected area oozes sappy liquid.
  • It will show up as dark or black spots that take over 1/3 of the leaf size. The black spots enlarge rapidly and begin spreading to other leaves.
Bottom leaf of Orchid getting yellow
Orchids under stress will exhibit primary signs, including yellowing and wilted leaves, followed by spots and smudges.
  • Dark spots are caused by bright lighting, and bacterial brown spots may appear tiny in size with brownish spots that later turn black.
  • If the black spots appear as elongated smudges, they are most likely Guignardia Leaf Spot, also known as fungal leaf spot.
  • Occasionally, leaf spots may leave yellowing leaves with tiny brown spots.

If the black rot reaches the crown of a monopodial (single-stemmed) Orchid, it will kill the plant.

These signs may require a further diagnosis to determine the exact problem.

How to Treat Black Spots on Orchid Leaves (6 Causes & Solutions)

Orchids respond quickly to the change in environment by exhibiting unusual signs, where a black spot on leaves is one of them. The primary step in treating your Orchid’s black spots is diagnosing the problem.

Let’s go over the quick overview table, which shows the causative agents and the symptoms.

Black SpotsReasonsSymptoms
OverwateringTips of leaves turning brown and later black
Bacterial InfectionWet lesions will appear that turn black
Fungal InfestationDiscolored leaves with tan or black spots
Extreme TemperatureBrittle and brown or black spots
Pest InfestationSmall holes and tiny black spots
Age DeclineOld and discolored leaves with slight blackening

Let us look at the possible causes of black spots in Orchid plants.

1. Overwatering and Water Quality

Start ruling out overwatering issues because it is often the major contributor to black spots in Orchids.

Orchid does not like sitting in a pool of water and is more likely to attract soil-borne fungi, leading to root rot.

It can cause the plant’s leaves to turn black, especially the tips, which may vastly differ from the black spots exhibited by the infected Orchid.

Black spots in Orchids
Overwatering causes dark brown to black tips in Orchid leaves.

However, remember that the plant has irreversible rot and cannot be saved by this stage.

Water quality is another consideration as the leaves start displaying discoloration if the watering source is highly mineralized such as mineral water.

Out of these two, water quality is of the least concern but not completely damage-free!

Solutions

  • Cut back on watering and slide the plant out to check for visible root damage such as dark, mushy, and smelly.
  • If the damage seems minimal, prune it away before applying fungicide and repotting in a fresh soil mix.
  • Dispose of the Orchid with severe root rot.
  • Follow a stricter watering schedule and use a soil moisture meter to assess the soil moisture every week or before watering.
  • Always use tepid and tap water or rainwater collected in a pot 12 hours before to moisten the Orchid potting soil.

2. Bacterial Infections

One of the most typical causes of black spots on Orchid leaves is the onset of bacterial disease. Bacterial leaf spots and soft rot are more common in Orchid plants.

a. Bacterial Leaf Spot

Bacterial leaf spot is familiar among Orchids left in damp or moist conditions.

It is caused by Xanthomonas campestris pv. vitians which is found in infected seeds; the bacteria thrive in wet and cool conditions.

You would notice small (less than 0.25 inch) water-soaked leaf spots on older leaves.

These lesions quickly turn black. As the disease proliferates, numerous lesions may begin to appear, causing the collapse of the leaves.

Black spots on Orchid leaves
Bacterial leaf spots will exhibit tiny black spots around the leaf.

b. Bacterial soft Rot

Bacterial soft rot is another cause of black spots on Orchid leaves.

It is caused by several gram-negative bacteria such as Erwinia, Pectobacterium, and Pseudomonas.

The pathogens secrete enzymes that decompose cell wall structures, destroying the plant tissue.

Moreover, temperature extremities and highly humid conditions may also result in soft rot diseases.

The pathogen associated with soft rot disease survives and quickly spreads from diseased to healthy plants under such conditions.

Although more prevalent in food crops, infected houseplants may spread bacterial soft rot to the Orchid plant.

Solutions

  • Start quarantining the infected plant and do not reintroduce them to other plants until fully treated.
  • Trim the leaves with black spots using the sterilized pruning shear and dispose of them immediately.
  • Move the plant to an open location with better air circulation and temperature between 65-80°F.
  • Apply 3% Hydrogen Peroxide on a cotton swab and dab the infected area.
  • Applying copper fungicide will help treat bacterial lead spots and soft rot.
  • You can also apply Cinnamon fungicide to the infected area.

Find out all the reasons for a drooping Orchid plant

3. Fungal Infection

Orchid plants grown at homes are prone to fungal infestation caused by infected plants and improper trimming.

a. Black Rot

Black rot, also known as crown and heart rot, is a common cause of black spots on Orchid leaves, which may have devastating results.

It is caused by fungi Pythium ultimum and Phytophthora cactorum, which develop and thrive in Orchid plants left in rainy or damp locations.

These fungi boast zoospores that can swim through the water and penetrate the plant tissue when water happens to be sitting on the Orchid leaf.

Black rot in Orchid
Fungal diseases cause black rot in the Orchid.

White mycelium and sporangia may appear on the plant, spreading to other portions of the plant, leading to untimely death.

You would mostly notice black smudge, which proliferates throughout the leaf.

b. Fungal Crown Rot

Fungal crown rot is another cause of root rot in Orchids and black spots on the leaves.

The causative agent is Fusarium pseudograminearum, which appears in an overwatered Orchid sitting in a cold and poorly ventilated area.

The infected areas may look discolored with tan or dark colors like black spots.

The worst thing about fungal crown rot is that the plant may die within weeks if untreated on time.

Solutions
  • Remove the diseased portion and healthy tissue surrounding the area using a sterile knife.
  • As an organic method, apply some grounded cinnamon to the infected parts.
  • Otherwise, apply chemical pesticides like Agri-Mycin if the infestation looks worse.
  • You can pour hydrogen peroxide into the infected area. Repeat the treatment every 2 to 3 days.

c. Fungal Leaf Spots

Fungal leaf spot, primarily caused by Phyllosticta capitalensis and Guignardia, is another cause of black spot on Orchid leaves.

It spreads quickly and causes unsightly blemishes on Orchid leaves. The fungal leaf spot disease is most prevalent in hotter climates.

The early symptom of Phyllosticta and Guignardia leaf spots shows tiny, dark purple, elongated lesions on either leaf surface that eventually turn black.

Spots frequently combine to form large irregular lesions that can cover a large portion of the leaf.

Guignardia and Phyllosticta leaf spot
Guignardia and Phyllosticta leaf spots are prevalent in many types of Orchids.
Solutions
  • Prune away infected leaves and safely dispose of them off.
  • Spray the plant with fungicides like thiophanate methyl and a protectant fungicide like Mancozeb, Dithane M45, Captan, and Ferbam.
  • Apply them repeatedly every 2 to 3 weeks following the label instructions.

4. Extreme Temperature and Sunburn

Extreme temperature and bright lighting will excessively transpire the leaves, leading to water loss.

It is indicated by low-humidity stress that causes dry spots and dark patches on Orchid leaves.

Your Orchid is more likely to suffer heat saturation when the condition exceeds 85°F, coupled with a lack of misting.

Black spot in Orchid leaves
Temperature extremities and bright lighting can cause black spots in Orchid leaves.

Check for brittle and brown or black spots on Orchid leaves.

Sunburn is another cause of the blackening of Orchid leaves, where they can even become brown and crispy around the edges when severely scorched.

However, do not mistake these for a diseased Orchid plant.

Solutions

  • Move your Orchid away from direct sunlight or brightly lit areas, such as close to the south-facing window.
  • Trim the leaves with excessive blackening (More than 50%), brownish patches, and holes.
  • Place the plant in a pebble tray filled with water to soak in the moisture naturally.
  • Mist the leaves with tepid water a couple of times a week to boost the humidity level around the plant.
  • Otherwise, move it indoors beside other houseplants or a room humidifier.

5. Pest Infestation

Although rare, the black spots on Orchid leaves may be the byproduct of pest infestation.

You heard it right! Pest invasion of the houseplants is not uncommon, especially when bringing the infected plant home.

Some common culprits include aphids, spider mites, scales, mealybugs, Thrips, gnats, and root mites, whereas aphids, scales, and mealybugs are more prevalent among Orchid plants.

Different pests in plants
Pest sucks out plant nutrients and leaves behind brown spots that later turn black.
PestsEffects of InfestationDiagnosis
AphidsCricket-like creatures with back legs that suck up saps from the plant leaves and stems.Especially abundant on stems and buds with higher nitrogen concentration
Mealy BugsThey eat the leaves sap, causing stunted and deformed development.Seen on new growth, leaf veins, and leaf joints
Scale InsectsDrains important plants sap, weakening them and causing their leaves to be yellow and fall off.Found on plant stems, twigs, trunks, foliage, or fruit
Spider MitesCausing leaves to turn yellow, brown, or gray and drop off.Reside on the undersides of plant leaves, where they weave silky webs around tree leaves and stems
ThripsSuck out plant's juice and leaves may appear pale, splotchy, and silvery before dying.Found on the leaves or stems of plants, as well as in the petals of flowers.

Most pest infestations would begin with contaminated potting soil, where the pest eggs would hatch larvae upon receiving a favorable environment.

As these larvae invade the plant’s shoots and leaves, they begin sucking the sap, leaving tiny black spots around the infected leaves.

Solutions

  • Deadhead all the infected parts, including leaves and stems, to avoid further damage.
  • Use Neem oil to apply all over the plant to remove the pests and their eggs organically.
  • Otherwise, dip cotton in 75% diluted isopropyl alcohol and rub the infected parts.
  • Use tweezers or your fingers to pick up the visible pests and drop them in the soapy water solution.
  • Apply chemical pest repellants like Malathion or Pyrethrin spray if the problem persists.

Related article; How to Identify Insect Eggs on Leaves and Treat Pest Infestation?

6. Age Decline

The Orchid plant will regularly decommission older leaves that look discolored and worn out.

Although rare, you may find some black spots on older leaves due to the dwindling Chlorophyll process.

Yellowing foliage in Orchid
An aging Orchid will exhibit many problems, including yellowing and wilted leaves, sometimes with black spots.

However, it does not mean your plant is infected or drying from a disease.

Start with diagnosing whether the infected leaves appear at the bottom half, and the sighting of black spots.

Old, discolored leaves are prevalent in the bottom half as they are first to come and first to go, and you may only witness a few blackening leaves.

Solutions

  • Prune your Orchid foliage regularly to give it a clean.
  • Remove dark, brown, dry, and wrinkled-looking leaves.
  • Check the bottom half for old and decayed leaves, which have to go.
  • Wash your plant with clean water or Neem oil several times in the growing season to keep it looking tidy.

How to Prevent Black Spots on Orchid Leaves?

Here are some in-handy tips to help avoid black spots in an Orchid plant.

  • Start with scheduling watering and moisture level to avoid the risk of overwatered plants and root rot.
  • Most Orchid species require watering every 5 to 10 days during spring and summer when the soil base is 90% dry.
  • Use a soil moisture meter before watering, which should read no more than 4 or 5.
  • Use a room humidifier to maintain an ideal humidity level around the plant. Orchids do best in humidity range between 40% to 70%
  • Orchid prefers a light range from 380nm to 430nm, best provided by dappled sunlight in an east-facing location or a few feet away from the south-facing window.
  • Ensure the temperature stays between 65-80°F (18.3-30°C) ranges throughout the growing period. Otherwise, move your plant under LED grow light in fall and winter.
  • Clean Orchid leaves a couple of times in spring and summer with a soapy water solution or Neem oil to prevent pest and bacterial disease.
  • Change soil appropriately and prioritize drainage using a soil mix rich in peat moss, perlite, fine bark, chips, and vermiculite.
  • Quarantine a newly bought plant for at least two weeks before introducing it to other houseplants.

Conclusion

Infected and sick Orchids are more likely to exhibit black spots on the foliage, which is a significant tell-tale sign.

Start diagnosing the problem with your Orchid using this guide upon discovering this tell-tale sign.

When loved and cared for, your Orchid will display healthy green foliage and lush blossoms yearly.

Follow this plant guide to diagnose the issues with your Orchid plant before it may become unsalvageable.

Related Article: Learn More About Orchid Plant Problems

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