How to prevent and treat stem rot in potted orchids? A detailed explanation of the disease patterns

Stem rot in potted orchids can also be called wilt disease or blight, and it is one of the most troublesome diseases among orchid species. The pathogen of orchid stem rot is Fusarium (a fungus). It may first appear as early as February, and May to September is the peak period for orchid stem rot. In severe cases, it causes the orchid stem to rot and shrivel until the plant dies.

I. Symptoms of damage

After an orchid becomes diseased, the base of the heart leaf of an old shoot or a new shoot begins to turn yellow, and within 1-2 days it will wither, turn yellow, and die. If the pot is turned out at this time, you can find that the root system of the diseased shoot is still intact, and there may even be crystal tips present, and the new buds produced that year are also intact. However, if you cut open the pseudobulb of the diseased shoot with a knife, you will find that the inside of the pseudobulb has already turned brown, or even rotted. If you continue cutting into the pseudobulb adjacent to the diseased shoot, you can also find that those shoots which look green and seemingly healthy already have pseudobulbs infected internally (turned brown); disease onset is only a matter of time. From this point, it can also be seen that the spread of stem rot is extremely hidden.

II. Disease patterns

A high-temperature and high-humidity environment, compacted potting medium, and poor ventilation make stem rot more likely to occur. The stem rot pathogen mainly overwinters in the potting medium as mycelium and thick-walled spores, and in the second year becomes the primary infection source. The pathogen spreads through contaminated potting medium and orchid shoots, invades through root wounds or natural openings of the orchid plant, infects the vascular bundles of the orchid plant, and multiplies in large numbers, then blocks the plant's water transport channels, causing the orchid plant to die from dehydration and lack of nutrients.

III. Control methods

1. Treat orchid plant wounds promptly. Immediately after dividing an orchid, apply a wound healing agent or a broad-spectrum fungicide to prevent infection.

2. Cut out diseased shoots promptly and destroy diseased plants.

3. Place potted orchids in a ventilated location.

4. During the peak period of stem rot, drench the pot with medication once every 15 days. The main options include 75% fenaminosulf soluble powder at 800-1000 times dilution, 25010 prochloraz emulsifiable concentrate at 800-1000 times dilution, and 70%? hymexazol wettable powder at 800 times dilution.