Watermelon Anthracnose

Isn’t it refreshing to eat a bite of watermelon on a hot summer day? Watermelon is a very popular fruit in summer because of its cool and delicious taste. But do you know that watermelon can easily be infected with watermelon anthracnose during planting? Farmers who grow watermelons should be more aware that this plant disease has a great impact on watermelon yields. Because the whole area is infected, not just a single individual.

Watermelon seedlings are invaded by this disease because they are infected by a fungus. There will be obvious changes in appearance. First, some small spots of rot will appear on the leaves of the watermelon seedlings, and then it will slowly spread until the watermelon is also infected.

Watermelon Anthracnose

1. Symptoms

Watermelon Anthracnose Watermelon Anthracnose Watermelon Anthracnose mainly harms leaves, but can also harm stems, petioles and fruits. When the seedlings are affected, circular or semicircular brown or dark brown spots appear on the edges of the cotyledons, often with dark brown halos around them. Small black dots or light red sticky substances are often scattered on the spots. The stems near the ground are affected, the base of the stems turn dark brown, and they become constricted, thin, and fall off suddenly. When the melon vine or petiole is infected, it initially appears as water-soaked yellow-brown oblong spots, which are slightly sunken and then turn dark brown. After the spots surround the stem for a week, the whole plant dies. The leaves are infected, initially appearing as round or irregular watermelon anthracnose stains, sometimes with ring patterns. The spots are easily broken and perforated when dry. When wet, a pink sticky substance appears on the lesions. When the fruit is infected, it appears as water-soaked, sunken brown circular spots or oblong spots, which often crack. When the humidity is high, a pink sticky substance forms on the spots.

2. Causes

Watermelon anthracnose is caused by infection by the fungus Colletotrichum of the Ascomycetes. The most suitable temperature for the disease is 22-27℃. The lesions stop growing below 10℃ and above 30℃. The pathogen overwinters in stumps or soil. When the temperature and humidity are suitable in the second year, the overwintering pathogen produces conidia and begins the initial infection. The pathogens attached to the seeds can directly invade the cotyledons and cause disease in the seedlings. Under suitable conditions, the pathogen will produce spore discs or conidia and infect again. Conidia are mainly spread through flowing water, wind, rain and people's production activities. When picking melons, if there are conidia on the surface of the fruit, it can also be infected and cause disease during storage and transportation.

The occurrence of watermelon anthracnose is closely related to humidity. Under suitable temperature, the higher the relative humidity, the more serious the disease. When the relative humidity is between 87% and 95%, the incubation period of the pathogen is only three days. The lower the humidity, the longer the incubation period. When the relative humidity drops below 54%, the disease will not occur. In addition, excessive application of nitrogen fertilizer, poor drainage, poor ventilation, excessive density, weak plants and repeated planting can cause serious disease.

3. Prevention and control measures

Field management

① Choose disease-resistant varieties such as Qihong, Qilu, Kaiza 2, Kaiza 5, Jingxin and Xingmi.

②Disinfect seeds and cultivate disease-free and strong seedlings.

③ Implement crop rotation, apply fertilizers rationally, reduce the use of nitrogen fertilizers, and increase the use of potassium fertilizers and organic fertilizers.

④ Cover the ground with ground film and strengthen ventilation and air conditioning to reduce indoor air humidity to below 70%.

⑤ Reasonable density planting and scientific pruning to prevent excessive density in order to reduce the humidity of the indoor microclimate.

⑥ Use fungicides and pesticides scientifically.

After introducing some characteristics of watermelon anthracnose, if you are a watermelon farmer or know a friend who grows watermelon, you can remind yourself and them. Once watermelon is infected with watermelon anthracnose, it will have a great impact on farmers and will directly affect their harvest.