Detailed Explanation of Pest and Disease Control Methods for Orchid Cultivation

(1) Orchid Anthracnose

Symptoms: This disease affects orchid leaves, often occurring at the leaf tips and leaf margins, and can also infect orchid fruits. When leaves are affected, small round or oval spots appear initially, then gradually expand; in the later stage, the center of the lesion becomes pale brown or grayish white, with dark brown or blackish brown edges, and the boundary between diseased and healthy tissue is distinct. The expansion of the lesion is often restricted by leaf veins; lesions at the leaf tip are often triangular, spreading downward from the tip. Lesions at the leaf margins tend to be semicircular, and the diseased tissue is brittle, sometimes splitting longitudinally. The size of the lesion varies with the width of the orchid leaf. Lesions on fruits are dark brown and spindle-shaped. In the later stage, black dot-like acervuli appear on the lesions.

Control methods:

① Prune off diseased leaves and burn them promptly.

② Strengthen cultivation management and maintain ventilation and light penetration in the orchid growing environment; water should be poured from the edge of the pot, avoiding overhead watering.

③ Chemical control. In the early stage of disease onset, spray 25% carbendazim wettable powder at 500 times dilution; 70% mancozeb at 600 times dilution. Spray 2 to 3 times consecutively depending on the severity of the disease, once every 7 to 10 days.

(2) Orchid Leaf Spot

Symptoms: Orchid leaf spot occurs on leaves, commonly in the middle of the leaf. The lesion is initially a brown spot, and after expanding it becomes elongated oval to long strip-shaped. The edges are reddish brown, and the interior is grayish brown. In the later stage, black granular bodies are scattered on the lesions, which are the pycnidia of the pathogen.

Control methods:

① Attention should be paid to timely pest removal and improving ventilation conditions.

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

(3) Orchid Round Spot Disease

Symptoms: Orchid round spot disease attacks leaves. Initially, small reddish brown spots appear on the leaves, rapidly expanding into semicircular or circular dark brown lesions. In the later stage, the center of the lesion gradually fades, with dark brown edges and a light brown center. On both the front and back sides of the center of the lesion, yellow-brown wart-like protrusions develop, which are the acervuli of the pathogen. When there are many lesions on a leaf, the tissue between the lesions loses its green color, turns yellow, and dies.

Control methods:

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

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