Orchid Diseases

Unfortunately, along with the pleasure of seeing your orchids come to bloom, there are a few negative aspects to orchid growing such as disorders and disease. Most orchid sicknesses are preventable by proper growing conditions. We hope you never encounter any of these.

Basal Rot

Basal rot is commonly known as ‘Southern Blight’. It is directly related to watering methods and practices. Either over watering, or water left standing in the crown of plants combined with cool humid situations can bring on this condition.

Basal rot, as the name suggests, starts at the bottom or the crown of the plant and proceeds upward. The condition is discovered on a plant with multiple growths, and only a small portion is afflicted, you can attempt to save the plant by cutting away the diseased portion with a sharp knife and treating the wound with sulphur. Keep on the dry side after the “operation” and hope the rot does not spread.


This is a fungal disease which affects primarily the flowers of phalaenopsis, cattleya, cymbidium and dendrobium. This condition occurs most frequently in cool, moist conditions where there is little air movement. Symptoms are tiny black spots on the petals which soon grow larger and in extreme circumstances are covered with a grey fuzzy mold. If caught early, take measures to increase night time temperatures to no less than 65 degree F and provide maximum air circulation.

Remove and destroy badly infected material such as dead flowers which have fallen to the floor and are covered with mold. Spray flooring with a strong solution of fungicide. Spray plants with a mild solution of physan or other liquid fungicide. This will not reverse the damage already manifest on your bloom, but should dry up the affected areas and halt the further spread of spores.

Fusarium Wilt

Not a disease in itself, but rather a common affliction due to poor culture or growing conditions. The most often contributing factor is severe shortage of water, especially during the growing season. This is evidenced by extremely shriveled, desiccated leaves. Over watering can produce the same symptoms once the roots have rotted and can no longer provide moisture to the plant.

Remedy: Pull the plant out of the pot. If there are no live roots, give it a decent burial because it will not be worth the time and effort spent to attempt a resurrection. If in the early stages however, and if there are still some viable roots present, you can attempt to save it.

Repot immediately in fresh moist orchid seedling mix. Put the newly potted plant in a more subdued light than where it was growing and keep the mix on the moist side, but not wet. Mist once or twice a day to help humidity.

Phalaenopsis Bud Blast

This is a condition where a seemingly healthy phalaenopsis orchid spike develops buds that do not fully open and turn yellow or shrivel and drop off.

The cause can be many things, the most common is root rot. Hot or cold drafts, over fertilizing, softened water and a number of other conditions including exposure to smoke from burning leaves or barbeques can be attributed to bud blast.

Pseudomonas Cattleyae

Pseudomonas cattleyae, also known as ‘brown wet spot’ occurs mostly in phalaenopsis. However, a similar wet bacteria infection can occur on other orchids as well.

Plants develop brownish black, soft areas usually starting on the underside of the leaves and quickly penetrating to the leaf surface. The cause is a combination of cool temperatures, high humidity and inadequate air movement. Prevention is easier than the cure. Keep minimum night temperatures around phalaenopsis at least 60 to 65 degrees F along with brisk air circulation. Brown wet spot can not develop under such conditions.

Remedy: If the disease has reached the crown portion of the plant, there is no cure even if some of the leaves look healthy. On phalaenopsis, if caught early, the affected portion of the leaf should be cut off (well below the afflicted area) with a new razorblade or some other sterilized cutting tool. Wet rot on other orchids must be treated by lancing and then cutting and/or scraping out the damaged tissue.

Orchid Virus

This is the most dreaded orchid disease because it can not be visually identified in its early stages. Orchid virus disease invades and kills leaf cells which condition in turn facilitates secondary bacteria infections. The disease has no preference to type or genus and can spread from plant to plant indiscriminately by insects or cutting implements. In the advanced stage, orchid leaves will display ugly black rings, circular or diamond shaped spots.

Unfortunately, there is no remedy or cure for orchid virus and the only positive way to know if your plant is infected is through laboratory testing. There are many other causes for black discoloration on orchid leaves and that condition in itself does not necessarily mean that your orchid is infected by virus.

Maintaining consistently clean growing conditions along with common sense cultural practices including optimum temperature and climate, will go a long way towards keeping your orchids healthy and in top condition.

What is the best way to deal with bacterial and fungal disease on my orchids?

The most efficient method to treat bacterial and fungal disease is the regular use of a systemic agent such as Phyton 27. The agent will be absorbed by the roots of the plant and then carried throughout the plant. Once the Phyton 27 is absorbed by the plant it will remain in the plant~s system for months.

How can I prevent bacterial and fungal diseases?

Orchids benefit from fresh air circulation. In their natural habitat, orchids get excellent air circulation, which helps prevent bacterial and fungal diseases. Avoid cold drafts from coming in contact with the plants as well.

Try to water the plants early in the day, so that the foliage will be dry by nightfall. To prevent bacterial and fungal disease use Physan 20 once a month.


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