Grape black pox is caused by Sphaceloma ampelimun de Bary, a genus of Deuteromycete subphylum Sphaceloma ampelimun. Grape black pox can infect grape leaves, fruits, new shoots, petioles, fruit stems, cobs, tendrils and inflorescences, especially the young and tender parts. When the disease is severe, branches and leaves will die and flowers and fruits will fall, causing serious losses.
1. Occurrence pattern
The pathogen mainly overwinters as mycelium on the diseased tissues of diseased leaves, vines or tips, and produces new conidia the following year, spreading the infection through rainwater. This disease is most likely to occur when grape plants grow under high temperature and high humidity conditions, and the optimal temperature for the disease is 25°C. Generally, when the grape leaves are spreading to the young fruits as big as soybeans, the humidity is high and the temperature is high, which is the peak period of the disease. The occurrence of black pox disease is also related to the breed. Varieties from the European breed group, such as milk and longan, are susceptible to disease. Varieties from the Western European breed group, such as red roses and rose scented roses, have moderate disease resistance. American and European-American hybrid varieties, such as Kyoho and Black Orin, have strong disease resistance.
2.Characteristics and identification methods
After being infected with the disease on young shoots, tendrils and petioles, brown round and oval lesions appear at first, and then turn gray-black and slightly sunken. In severe cases, the lesions are connected and the diseased tips dry up. When the leaves are damaged, many water-soaked brown round spots appear, which gradually expand. The edges of the lesions are dark brown, the center is gray-white, and they are slightly sunken. Later, they dry up and become perforated. After young fruits are infected, many nearly circular light brown spots appear on the fruit surface. The periphery of the lesions is purple-brown, and the center is gray-white and slightly sunken, like a bird's eye. Infected fruits grow slowly, are green, hard in texture and sour in taste, and lose their edible value.
3. Use pesticides
(1)Carbendazim
Dosage form: Carbendazim 50% WP
Control period: After the leaves unfold and before the fruits color, spray alternately with other fungicides every 10 days or so for control.
Instructions: Use 15 grams of 50% carbendazim wettable powder, mix with 15 kilograms of water, dilute it to a 1000-fold solution, stir and spray evenly.
Precautions: Carbendazim can be mixed with general fungicides, but when mixed with insecticides and acaricides, it should be mixed and used. It should not be mixed with alkaline agents. Long-term single use of carbendazim can easily cause bacteria to develop resistance, so it should be used in rotation or mixed with other fungicides; when used for soil treatment, it will sometimes be decomposed by soil microorganisms, reducing the efficacy of the drug. If the soil treatment effect is not satisfactory, other methods can be used; the safety interval is 15 days.
Dosage form: 70% WP
Control period: Spray alternately with other fungicides every 10 days or so after leaf expansion and before fruit coloration.
Instructions: Use 15 grams of 70% chlorothalonil wettable powder, add 15 kilograms of water, dilute it to a 1000-fold solution, stir and spray evenly.
Precautions: Chlorothalonil cannot be mixed with alkaline pesticides such as lime sulfur mixture and Bordeaux mixture; this product should be protected from moisture and sun, and stored in a cool, dry and ventilated place.
(3)Arsine · Zinc · Thiram
Dosage form: Thiram 50% WP
Control period: Spray alternately with other fungicides every 10 days or so after leaf expansion and before fruit coloration.
Instructions: Use 15 grams of 50% sterilizing wettable powder, add 15 kilograms of water, dilute it to a 1000-fold solution, stir and spray evenly.
Precautions: It cannot be mixed with medicines containing copper, mercury, and aluminum; this medicine contains thiomearsine, which is prone to phytotoxicity, so care should be taken to control the dosage.
(4)Desenzinc
Dosage form: 65% WP
Control period: Spray alternately with other fungicides every 10 days or so after leaf expansion and before fruit coloration.
Instructions: Use 30 grams of 65% zinc wettable powder, add 15 kilograms of water, dilute it to a 500-fold solution, stir and spray evenly.
Precautions: It should be used in the early stage of the disease to achieve preventive effect; it cannot be mixed with copper preparations or alkaline drugs; safety precautions should be paid attention to when using medicine.
