1. Anthracnose of Orchids

Symptoms: This disease affects orchid leaves, commonly occurring at the leaf tips and margins, and can also infect orchid fruits. On leaves, the disease initially appears as small, round or oval spots, which gradually enlarge. Later, the center of the lesion turns pale brown or grayish-white, while the edges become dark brown or blackish-brown, with a clear boundary between diseased and healthy tissue. The expansion of lesions is often limited by leaf veins; lesions at the leaf tip are often triangular, spreading downwards from the tip. Lesions on the leaf margins are often semi-circular, with the affected area being brittle and sometimes cracking longitudinally. The size of the lesions varies with the width of the orchid leaves. On fruits, lesions are blackish-brown and spindle-shaped. Later, small black dot-like conidiophores appear on the lesions.

Prevention and control methods:

① Remove diseased leaves and burn them promptly.

②Strengthen cultivation management and maintain good ventilation and light in the orchid cultivation environment; water should be poured from the edge of the pot to avoid direct watering.

③ Chemical control. At the initial stage of disease, spray with a 500-fold dilution of 25% carbendazim wettable powder or a 600-fold dilution of 70% mancozeb. Spray 2-3 times consecutively, once every 7-10 days, depending on the severity of the disease.

2. Orchid leaf spot disease

Symptoms: Orchid leaf spot disease occurs on the leaves, commonly in the middle of the leaf. The lesions initially appear as brown spots, which enlarge into elongated oval to long stripes. The edges are reddish-brown, and the interior is grayish-brown. In later stages, black granular substances, which are the conidiophores of the pathogen, are scattered on the lesions.

Prevention and control methods:

① Pay attention to timely pest control and improve ventilation.

②During the disease period, regularly spray with 0.3%-0.5% Bordeaux mixture or 800 times dilution of 65% zineb.

3. Orchid spot disease

Symptoms: Orchid leaf spot disease affects the leaves. Initially, small reddish-brown spots appear on the leaves, rapidly expanding into semi-circular or circular dark brown lesions. Later, the center of the lesions gradually fades, with dark brown edges and a light brown center. Yellowish-brown wart-like protrusions, the conidiophores of the pathogen, appear on both sides of the center of the lesions. When there are many lesions on the leaves, the tissue between the lesions loses its green color, turns yellow, and dies.

Prevention and control methods:

① Remove diseased leaves and burn or bury fallen leaves to reduce sources of infection.

②During the growing season, use 1:1:100 Bordeaux mixture or 70% chlorothalonil at a dilution of 500 times for prevention and control.