Harmful symptoms and preventive measures of brown rust in orchids

Orchids are one of China's traditional famous flowers, with a cultivation history of more than 1,000 years and high ornamental value, and are deeply loved by flower enthusiasts. However, during actual cultivation, brown rust damage can occur, greatly affecting the growth and development of orchids, and in severe cases even causing orchid plants to die. Therefore, today the editor will discuss the harmful symptoms and preventive measures of brown rust in orchids.

I. Causes and symptoms

The pathogen of brown rust in orchids is Uredo rust fungus (a fungus). Because orchid varieties differ, their symptoms also vary. One type infects the upper surface of orchid leaves, causing many yellow-brown powdery spores to appear on the leaf surface and leaving striped markings on the leaf surface, while the underside of the leaf generally shows no other symptoms; in severe cases, it causes the leaves to dry out and die. The other type damages the underside of orchid leaves, causing reddish-brown small spots to appear on the leaf underside, which in the later stages of damage merge into large striped patches densely covered with rust spores.

II. Disease occurrence patterns

During orchid cultivation, low temperatures, many wounds on orchid leaves with moisture retained for long periods, and overly wet orchid growing medium are important causes of brown rust in orchids. Brown rust generally occurs in early spring each year. Brown rust symptoms can be seen in mid-February, and rust spores can be seen in April.

Although brown rust only causes orchid plants to grow weakly and does not cause orchids to die, if corresponding control measures are not taken after the disease occurs, brown rust will quickly spread to other orchid plants, causing the orchids to lose their ornamental value.

III. Preventive measures

1. Thoroughly prune diseased and remnant tissues

Inspect the diseased leaves on orchid plants pot by pot and leaf by leaf. If diseased leaves are found, they must all be pruned off, and pruning should also extend 2 cm into the healthy part. After pruning, burn or bury these diseased and remnant leaves in a centralized manner, which can reduce the source of pathogens.

2. Preventive application of chemicals

Spray once every half month with a 500-fold dilution of 70% mancozeb wettable powder, for 2 consecutive sprayings. When spraying, it should be uniform, especially on the underside of leaves, the pot surface, and the surrounding environment.

3. Treatment of diseased plants

Dilute 77% copper hydroxide wettable powder or 75% chlorothalonil wettable powder, etc., into a 500-fold solution and spray once every 7 days to prevent brown rust.