What fungicide to use for orchid leaf blight? Latest effective fungicide recommendations

Orchid leaf blight is a relatively serious disease harming orchids. It usually spreads quickly to the branches and leaves of the orchid and develops very fast. In just a few days the entire diseased seedling turns yellow and withers, somewhat similar to soft rot, except that after the leaf blight diseased plant dies there is no off-odor, while a soft rot diseased plant, when pulled up and smelled, has a foul odor. Now let us take a look at what fungicide to use for orchid leaf blight!

Symptoms of orchid leaf blight

In orchid leaf blight, the diseased seedlings on one side of either new growth or old growth begin to turn yellow (in metabolism, at most the leaves turn yellow one patch at a time, whereas this disease makes almost the entire plant turn yellow at the same time. In metabolism only the old leaves turn yellow, while leaf blight attacks regardless of old or new growth). In just a few days the entire diseased seedling turns yellow and withers. In severe cases, plants become diseased one after another until the entire pot of orchids dies.

Occurrence pattern of orchid leaf blight

Orchid leaf blight is a disease caused by fungi, and the pathogen is Colletotrichum orchidearum. The pathogen overwinters or oversummers on diseased leaves. When conditions are suitable, the pathogen spreads and propagates by wind and rain and by water droplets splashing during watering. It mainly invades through wounds, but can also directly invade through the epidermis of tender leaves. April to July is the disease period for old leaves, and late May to June is the peak disease period. July to November is the disease period for new leaves, and new leaves are affected more severely than old leaves. In the Guangdong area, disease begins in mid-December each year, damage is severe in March of the following year, and after May the disease tends to stabilize. It is prone to occur under suitable temperatures, high relative humidity, or moist leaf surfaces. It is severe where soil is compacted, potted flowers are placed too densely, and ventilation and light transmission are poor.

What fungicide to use for orchid leaf blight?

1. Strengthen management: The greenhouse should be ventilated and let in light, flower pots should not be placed too densely, and new soil should be replaced when potting. Promptly remove diseased leaves and their residues to eliminate the source of infection and prevent the disease from spreading.

2. Chemical control: Before disease onset, 0.5-1% Bordeaux mixture, or 65% zineb wettable powder at 600-800 times dilution, can be sprayed once every 7-10 days, giving good protective effect. During disease onset, 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.