How to prevent and control anthracnose in orchids?

OrchidsThe most common and widespread disease is anthracnose. This disease affectsorchidleaves, and often occurs onorchidleaf tips and edges. When a leaf is affected, small round or oval black spots appear at first, then gradually expand; in the later stage, the center of the lesion becomes light brown, or the edge becomes dark brown or blackish brown, with a clear boundary between diseased and healthy tissue. The expansion of the lesion is often limited by the leaf veins; lesions on the leaf tip are often triangular and spread downward from the leaf tip. Lesions on the leaf edge are often semicircular, the diseased tissue is brittle, and sometimes splits longitudinally. The size of the lesions varies with the width of the orchid leaf.

Damage situation. This disease mainly affectsCymbidium goeringii、Cymbidium ensifolium, Cymbidium faberi and many other orchids. Affected plants develop large numbers of lesions on the leaves, affecting growth and ornamental value.

Occurrence pattern. The pathogen of this disease belongs to the Deuteromycetes among fungi, and overwinters as mycelium in host residues or in the soil. In the second year, conidia are produced in spring and spread by wind and rain, invading through wounds on orchid leaves and other sites, and spreading and causing infection repeatedly in the same way. The disease occurs most severely from July to September.

Prevention and control methods:

1. Cut off diseased leaves and burn them promptly.

2. Strengthencultivationmanagement, keep the orchidcultivationenvironment well ventilated and well lit, and water from the edge of the pot, avoiding splashing water on the leaves.

3. In the early stage of the disease, spray 2 to 3 times with 50% carbendazim wettable powder at 500-600 times dilution, or 70% thiophanate-methyl at 1000 times dilution, or an equal-amount 100-200 times Bordeaux mixture.