Orchid Leaf Blight Control Measures and Mushroom Topdressing Methods

Symptoms occur mainly on orchid leaves. In the early stage, the lesions are dark brown and nearly circular; lesions occurring at the leaf margins are semicircular. They then rapidly expand into large oval spots with a diameter of up to more than 20 mm, with dark brown edges and centers that gradually turn light brown, sometimes with one or two rings of lighter-colored concentric rings.

Control: a. Strengthen cultivation management: the greenhouse should be well ventilated and well lit, flower pots should not be placed too densely, and new soil should be used when potting. b. Remove sources of infection: promptly remove diseased leaves and their debris to eliminate sources of infection and prevent the disease from spreading. c. Chemical control: before the disease occurs, 0.5-1% Bordeaux mixture, or 65% zineb wettable powder at 600-800 times dilution, can be sprayed once every 7-10 days, providing good protective effect; during the disease period, 50% carbendazim at 800 times dilution or 75% thiophanate-methyl at 1000 times dilution can be sprayed, both of which can control the spread of the disease.

Disease development pattern: the fungus overwinters on diseased leaves and their debris, and spreads via wind and rain and splashing during watering. It generally enters through wounds, and can also directly invade young leaves. The pathogen can only expand and cause disease under suitable temperature and relatively high humidity conditions. Compacted soil and flower pots placed too densely with poor ventilation and air movement all make the disease more likely to occur.