Symptoms and prevention of bitter melon anthracnose

Bitter melon anthracnose is a very serious disease that will affect the growth and yield of bitter melon. So how can we better prevent and control it?

1. Harmful symptoms:

The leaves, stems, and melon strips can all be affected during the seedling and adult stages. When the disease occurs in the seedling stage, brown semicircular or circular lesions appear on the edges of the cotyledons, which are slightly sunken. When the disease occurs in the adult stage, the leaf lesions are nearly circular, of varying sizes, initially water-soaked, and quickly dry up to become reddish-brown, with yellow halos on the edges. Often several small lesions are connected together to form irregular large lesions. There are small black dots on the lesions. When it is humid, there is a pink sticky substance on the lesions. Under dry conditions, the lesions often crack and perforate. The lesions on the stems are grayish white to dark brown, slightly sunken, and can be affected on the surface. The lesions are nearly circular, initially light yellow-brown, and then turn reddish-brown to brown, and are slightly sunken. When the humidity is high, the lesions have light pink mucus overflowing. When the disease is severe, the diseased part expands, which can cause the melon strips to rot.

2. Disease pattern:

The pathogen attaches to the surface of seeds with mycelium, or overwinters in the soil with diseased residues. When sowing infected seeds, the pathogen can infect the cotyledons when the seeds germinate, causing the seedlings to become ill. The pathogen in the soil is transmitted to the plants through rain splashing and irrigation water, causing the disease. In addition to seed transmission, the conidia produced on the diseased plants can be spread by wind and rain, insects and agricultural operations for re-infection. High temperature and high humidity are the main conditions for the occurrence and spread of bitter melon anthracnose. Under suitable temperature conditions, the higher the air humidity, the easier it is to get sick, and the shorter the incubation period. When the relative humidity is 87-95%, the incubation period is 3 days, and the temperature is less than 54%, there is no disease. The disease can occur at a temperature range of 10-30℃, with the most severe disease at around 24℃ and mild disease above 28℃. Excessive use of nitrogen fertilizer, excessive irrigation, and continuous cropping will cause severe disease, and mature melon strips will have poor disease resistance.

3. Comprehensive prevention and control measures:

1. Choose disease-free seeds. Disinfect the seeds and harvest them from disease-free plants. Soak the seeds in 55°C warm water for 15 to 20 minutes, or soak them in 40% formaldehyde 150 times solution for 1 hour, 100 times solution for half an hour, or 50% mancozeb 500 times solution for 1 hour. Take them out and rinse them with clean water before sowing.

2. Raise seedlings in disease-free soil and cover with plastic film. Apply sufficient basal fertilizer and increase the application of phosphorus and potassium fertilizers. Control irrigation appropriately and drain water in time after rain.

3. Strengthen field management. Remove early diseased melons and leaves in time to reduce the effective source of bacteria in the field. Binding vines, harvesting and other agricultural operations should be carried out after the dew has dried to avoid human transmission. After harvesting, thoroughly remove diseased remains in the field and bury or burn them.

4. Chemical control. Chemical control should be carried out in time at the early stage of the disease. The chemical can be 75% thiophanate-methyl wettable powder 500-600 times diluted; or 50% carbendazim wettable powder 500 times diluted; or 70% thiophanate-methyl wettable powder 800 times diluted; or 80% anthrax thimerosal wettable powder 800 times diluted, etc. The above chemicals can be used alternately, sprayed once every 7 days, and continuously for 3-4 times, which can achieve good control effects.