A Detailed Guide to the Prevention and Treatment of Common Orchid Diseases
1. Phytophthora disease Symptoms: It occurs all year round, but is most severe during the plum rain season, when watering is too wet or ventilation is poor, and seedlings that have just come out of the flask are especially vulnerable. Brown spots form at the infected site, and under high temperature and high humidity they rapidly expand, eventually becoming dark brown patches, with leaves dropping and stems rotting until the plant dies. Prevention and treatment methods: ...
1. Phytophthora disease
Symptoms: It occurs all year round, but is most severe during the plum rain season, when watering is too wet or ventilation is poor, and seedlings that have just come out of the flask are especially vulnerable. Brown spots form at the infected site, and under high temperature and high humidity they rapidly expand, eventually becoming dark brown patches, with leaves dropping and stems rotting until the plant dies.
Prevention and treatment methods:
(1) Avoid excessive moisture, improve ventilation and air circulation, and ensure sufficient light
(2) Avoid the exclusive use of nitrogen fertilizer, to reduce soft, spindly plant growth
(3) Spray with 1/800 Duojunqing or 1/1000 Haoshengling solution
(4) Apply Dasheng powder to the wounds cut on diseased plants, then place them in a dry spot and do not water for one week, which can halt the spread of the disease.
2. Anthracnose
Symptoms: Plants grown too densely, with poor ventilation, imbalanced moisture, or wounds from injury are prone to infection. In the early stage of the disease, small brown sunken spots appear on the leaves, which later expand into round or irregular lesions, and in severe cases the center of the lesion shows necrosis.
Prevention and treatment methods:
(1) Do not plant too densely. Increase light; drainage and ventilation need to be good
(2) Cultivate strong seedlings, and do not move plants around frequently, so as to avoid injury and infection
(3) Cut off the diseased leaves, and apply 1/500 Dasheng-45 solution or 1/800 Wanjunqing to the wounds
(4) Spray once a week with 1/1000 thiophanate-methyl or carbendazim solution
3. Soft rot
Symptoms: This disease is more likely to occur in spring and summer under high temperature and high humidity, poor ventilation, and excessive application of nitrogen fertilizer. In the early stage, bacteria invade the leaves or heart leaves and produce water-soaked lesions, which rapidly expand and contain much water; in the later stage a foul odor develops, the diseased leaves turn yellow and drop off, and the whole plant soft-rots and dies. The disease spreads extremely rapidly and must be controlled as soon as possible.
Prevention and treatment methods:
(1) Improve growing conditions, increase ventilation, and lower temperature and humidity
(2) Excise the infected parts and apply antibiotic powder; do not water for one week, which can halt the spread of the disease
(3) Use 1000-fold streptomycin solution, or 500-fold lime-sulfur mixture or Bordeaux mixture, spraying once a week
4. Leaf blight
Symptoms: Small black spots appear at the leaf tips and gradually expand into irregular lesions; the edges of the lesions become dark brown while the center is pale grayish brown, and in severe cases they spread over the entire leaf, which finally withers and drops.
Prevention and treatment methods:
(1) Cut off the diseased leaves, and spray with 500-fold Dasheng-45 or 1000-fold Haoshengling
(2) For infected plants, avoid rainwater or suspend watering temporarily to prevent the condition from worsening
(3) Spray 500-fold Dasheng-45 once daily on a regular basis as a preventive measure
5. Southern blight
Symptoms: Cymbidium orchids are more prone to this disease. In the early stage the base of the pseudobulb turns black and rots, and white mycelium gradually develops on the lesions; the diseased plant gradually withers and dies.
Prevention and treatment methods:
(1) Cut off the pseudobulbs with lesions, and burn them together with the planting pots and growing medium
(2) Spray once a week with 500-fold Dasheng-45 solution, or 1000-fold carbendazim solution.