PESTS AND DISEASES
Root, stem and leaf rot from a poorly drained potting medium are the most common issues facing moth orchids. Aphids, spider mites and mealybugs can sometimes be a problem. Some experts advise targeting pests with a dab of methylated spirits to kill them. Black spots appearing on the leaves tend to be caused by a fungus; normally one that thrives in damp conditions. Affected leaves may also turn yellow. Leaves that show signs of black spot should be cut off to remove those areas affected by the fungus.