Brown Spots on Phalaenopsis Leaves

Water-Soaked Spots

• Bacterial soft and brown rot is a disease that exhibits itself as small, water-soaked spots on foliage. The spots may be surrounded by yellow and can quickly take over the plant, killing it off within a few days. This bacterial infection often enters the plant through wounds. Remove infected parts with sterilized scissors, or apply a bactericide, such as a copper compound. Apply the chemical to the plant and nearby plants that could be infected. Avoid overhead watering to prevent the spread of the disease, and improve air circulation to keep foliage dry

Blister Spots

• Bacterial brown spot, from the acidovorax or pseudomonas bacteria, appears as small water-soaked blisters that change from green to brown or black. It eventually dries up into a sunken blister that releases liquid filled with the bacteria. The infection spreads rapidly in Phalaenopsis species and can kill plants once it reaches the crown. Remove infected leaves with sterilized scissors and apply copper compounds to treat this problem. The disease thrives in heat and humidity. Improve air circulation and reduce these factors to treat and prevent this infection.

Chlorotic Spots

• This condition could be caused by a microfungus or a virus and is commonly seen in Phalaenopsis plants, though its cause is often difficult to determine. The condition may also be caused by microscopic mites. Yellowing and chlorosis develops into necrotic, sunken, darkened spots. Leaf edges appear burnt and red-brown colors appear on lower leaves. Spray with a fungicide to clear the infection if it appears a fungus is responsible. If you believe mites may be to blame, spray with miticide to treat.

Other Fungal Diseases

• Warm, humid and damp conditions are ideal for the care of phalaenopsis plants, but poor drainage may result in rotting, such as fungal root rot. This disease can cause brown, rotting spots on foliage. Cercospora fungal infections cause yellow, irregular spots that become necrotic and turn brown to black. Guignardia creates tiny dark-purple lesions all over the leaves. The septoria fungus causes yellow lesions that turn dark brown on the plant. Treat these fungal infections by removing affected leaves, spraying with a fungicide and reducing leaf wetness.