Orchids and Fungus

Asked April 17, 2016, 3:38 PM EDT

What is the best product to treat orchids with fungus? My father recalls a once a month soak treatment his grandmother used (made from a store bought powder) that worked really well but can't remember the name of it.
Thanks,
Jen

Broward County Florida

1 Response

Jem

Fungal diseases in orchids range from merely cosmetic to potentially fatal. Fortunately, there are treatments available to control most early fungal infections. The first and best defense against fungal attacks is cultural: don't let your plants stay wet, never head into a night with wet plants, and provide plenty of strong airflow to keep your plants healthy. Allow the medium to dry between waterings for most orchids. Practice good orchid culture and you can prevent the worst of the fungal disorders most of the time. Also, many minor fungal issues, such as minor black-spotting on leaves, can be tolerated without using chemicals. Simply removing the affective leaf can be adequate.

If the entire plant is affected it is probably best to discard the plant and medium and sterilize the container with a 10% bleach solution as the fungus will spread quickly to other plants.

If you have more than one plant with fungus it is probably best to not apply the home made remedies to all the plants until you make sure the plant will not be affected by the remedy.

You mentioned a white powder that your great grandmother used. It is probably baking soda and here is a formula for a solution that can be made with the baking soda. Initially the entire plant shojuld be treated roots and all. So the medium must be discarded and the pot sterilized or discarded.

Baking Soda formula

Anthracnose, Phytophthora, Botrytis, mildew, black spot, and leaf spot can all be treated with baking soda mixed at a rate of 4 tsp/gal. Add 2 tsp./gal of refined horticultural oil or insecticidal soap. Reapply every two weeks. If this doesn't work, try copper fungicide. It seems like it would be a good idea to wash the plant with clear water between applications to prevent a build up of the powder on the leaves and roots.

If this doesn’t work there are commercial fungicides available at your nursery store or large hardware stores. The systemic ones are the best if the plant is already infected. Make sure they can be used in the house I these are indoor plants.. There are also commercial prevention fungicides. Read all the instructions before purchasing and using. Again the medium and pot should be sterile since the fungus can be living in the roots, pot and medium.

Prevention

I have never personally used this mix for fungicide prevention but a formula recommended on the internet using cinnamon is given below. I have used a variation of this it to help control scale and it seems to work well, not perfectly, but does offer some control.

Spray – combine 2 tablespoons of cinnamon powder into a pint of isopropyl alcohol, shake well and let stand overnight. Filter solution through a coffee filter and use the brown liquid as an all-purpose fungicide spray. For a combination fungicide/insecticide – put 1 cup of the cinnamon/alcohol extract into a pint bottle, add 2 tablespoons of dishwashing detergent and top off with water. Use as a spray.

My version of this it to put a cinnamon stick into the alcohol/water mix that I use for a weekly morning spray on the plants. I then only replace the water/alcohol mix leaving the stick in the spray bottle until it is used up.

I hope this helps. Enjoy your orchids.

Tony