Diseases of Cymbidium Orchids – Viet Nam Agriculture

The colorful, thick and waxy petals of a cymbidium orchid stand out in any greenhouse. These beautiful flowers come in a wide variety of shapes and sizes, and every color except blue and true red, according to Colorado State University Extension. Cymbidium orchids put on a flower show only once a year, and they require specific conditions to bloom. They also are fairly susceptible to many diseases common to the orchid family.

Black rot, or Pythium ultimum, is a soil-borne pathogen that causes root rot and damping off in orchids. The plant’s roots and bulb will quickly turn black and rot, and the bulb then dries out. Black rot’s spores are spread through water. Poor drainage and too much water will encourage the pathogen’s growth. To get rid of black rot, apply mefenoxam, then steam or chemically treat your orchid’s growing medium, according to the University of California.

Bar mottle, also known as Cattleya severe flower break virus, causes yellow, bar-shaped streaks and blotches on the strap-like leaves of cymbidium orchids. The flowers generally are not affected, but they will be smaller and fewer. Sometimes the virus distorts the sepals and petals. Green peach aphids spread the virus, which you can contain by getting rid of the insects.

Sclerotium, or Sclerotium rolfsii, also known as collar rot, causes orchids’ leaf bases and stems to quickly rot and collapse. When the disease is present, you will see white fungus and small blotches that look like mustard seeds on the orchid and its planting medium. A warm, moist planting medium is ideal for the fungus, which can survive in soil for many years. Destroy any infected plants.

Mosaic, or the Cymbidium mosaic virus, has a great variety of symptoms. On young leaves, small, elongated pale areas will turn into dead, dark spots or streaks as the plant matures. If mottling appears on young leaves, it may disappear as the leaves age. The virus does not affect the flowers. Pruning tools transmit the virus, according to the University of California. Disinfect your tools between cuts and between plants. Infected plants cannot be healed, and you should destroy them.

Flower spotting, or Botrytis cinerea, is a fungus that causes small, brown, black or almost colorless spots to appear on leaves, surrounded by water-soaked areas. The fungus’s spores are airborne and thrive in cool, moist conditions. When watering your orchid, avoid wetting the flowers. To get rid of flower spotting, lower the humidity in your growing area and immediately throw away flowers and leaves as they die.