The first step in treating the dark spots on your orchid isdiagnosing the problem.
Some phalaenopsis have naturally mottled leaves, so it may be natural coloration.
However, leaf spotting can also signify a bacterial orfungal disease.
The Spruce / Ulyana Verbytska
However, keep in mind that black rot is highly contagious and can spread from plant to plant.
What Is Black Rot on Orchids?
Black rot is a fungal disease that causes root rot.
resulting from one or both of the fungiPythium ultimumandPhytophthora cactorum, black rot affects a widevariety of orchids.
Left untreated, the affected plant or plants may infect others and will probably die themselves.
The black spot or spots enlarge rapidly and can spread throughout the plant.
If your orchids are outside, keep them 3 to 4 feet above the ground to avoid splash contamination.
At first signs of infection, segregate all affected plants to avoid contaminating healthy plants.
Place the plant in an area that receives good air circulation to allow the cut to dry.
This paste is fairly waterproof and can be used to cover the wound.
Drenching the affected plant with a fungicide is also an option.
Drenches of a protectant fungicide such as Truban or Terrazole are recommended if the disease is diagnosed early.
For more advanced cases, a systemic fungicide such as Aliette or Subdue is more effective.
A mild fungicide can be made at home with cinnamon.
Steep cinnamon sticks in hot water overnight, and then remove the sticks, making cinnamon tea.
Watering an orchid with this tea can help battle fungus.
Overwatered orchids often have yellow or browning leaves that are likely to be droopy and wilting.
The roots will be visibly brown and mushy to the touch.
Orchids: Problems.Missouri Botanical Garden.
Fitch, Charles Marden.The Gardener’s Guide to Growing Orchids.
Brooklyn Botanic Garden, 2004
