Causes and Solutions for Stem Rot in Phalaenopsis Orchids

Stem rot in Phalaenopsis orchidsis a common and often fatal disease, mostly caused by overwatering and poor ventilation. If you do not act in time to save the plant, it usually1-2withers within weeks. Below is an effective rescue procedure for stem rot in Phalaenopsis orchids.

1. Treatment

1.Cutting away the diseased tissue

Using a sterilised cutting tool, cut upward from the base of the diseased stem until the cut surface shows white, healthy tissue. If the roots have already rotted, cut them all away and keep only the aerial roots that have not changed colour.

2.Disinfection

Soaking method: place the roots in 500-times-diluted carbendazim solution and soak for20minutes to kill pathogens deep within the tissue.

Spraying method: use 3% hydrogen peroxide to spray the wounds and remaining roots evenly; it disinfects by oxidation and promotes healing. White foam forming is normal.

3.Air-drying the roots

Place the treated plant in a cool, ventilated spot, away from direct sunlight, suspended in the air or laid flat on dry paper towels. In summer,1-2 days, and in winter2-3 days, until the wound is completely dry and scabbed over.

2. Repotting and substrate selection

Substrate requirements: use a mix of sphagnum moss+bark. The sphagnum moss should first be soaked in carbendazim solution for30 minutes and then drained, so it is loose and airy and does not hold standing water.

Potting tips: spread a layer of expanded clay pellets at the bottom of the pot to improve drainage, place the plant in the pot, and gently wrap the substrate around the roots, avoiding pressing it down too firmly. Leave the base of the stem exposed by1-2 cm to prevent it from being buried and rotting a second time.

3. Aftercare

Temperature: keep it at18-28°C, avoiding temperatures below15°C or above30°C, as this affects healing.

Humidity: keep air humidity at60%-70%, which can be adjusted with a humidifier, but keep it away from direct spraying onto the plant.

Light: place it in bright, indirect light, an east-facing windowsill is best, and ventilate2 times a day.

Watering: do not water for 3 days after potting; once the wound has healed, water by the soak-and-drain method, keeping the substrate slightly moist.

Fertilising: do not fertilise for1 month; once new roots have grown, spray with liquid orchid fertiliser.

4. Points to note

1.Check the base of the stem and the roots every week. If you find new rotten spots, repeat thecutting > disinfection > air-drying procedure.

2.If the plant keeps wilting and no new roots emerge, you can try a water-culture rescue: soak the base in 1/2-depth clean water and change the water every2 days to encourage new root growth.

3. Stem rot is highly contagious. During treatment, avoid contact with healthy plants, and used substrate must be sterilised at high temperature or discarded. If there is no improvement within1 month, it is advisable to discard the diseased plant to prevent it from infecting other plants.