Prevention and treatment of papaya mosaic disease with yellow and green symptoms in tender leaves

Papaya ring spot mosaic disease, commonly known as mosaic disease, occurs in the main growing areas of papaya.

papaya mosaic

Symptoms: In the early stage of the disease, water spots appear between the branches of stems, veins and tender leaves, followed by yellow and green or dark green and light green mosaic symptoms on the tender leaves of papaya, and water-stained round spots appear on the epidermis of infected papaya fruits, several round spots are connected into irregular large spots. At low temperature stage, most leaves of diseased plants shed and young leaves were deformed.

2. Pathogen and transmission: The pathogen of papaya mosaic disease is papaya mosaic virus, papaya ring spot virus and papaya abnormal leaf virus. Myzus persicae and Aphis gossypii are natural vectors of papaya virus with high transmission rate. Friction is easy to transmit poison, and the leaves of diseased plants in the field can be infected after contact and friction with the leaves of healthy plants.

3. Conditions of incidence: 1. Climatic conditions. Warm dry years, severe occurrence. Therefore, in Guangzhou area, there are two peak periods of disease and one green period of diseased plants in a year. 4-5 From October to early November, when the monthly average temperature is 20-25℃, the diseased plants are the most, and the symptoms are the most obvious; from July to August, the average temperature is 27-29℃, which is the green period of the diseased plants, and the symptoms disappear or slow down. High temperature can inhibit the virus, the diseased plant heated to 40℃ every day, 4 hours for 4 days, the diseased plant obviously turned green, the disease spots disappeared, but stopped a few days later, the symptoms reappeared.

2. Location of orchard. Because papaya mosaic disease is mainly infected by aphids, papaya plants adjacent to old orchards or diseased plants have a fast incidence and a high incidence. Papaya garden planted year after year has early onset and high incidence rate.

3. The growth period and growth status of papaya plants. Papaya can be infected with ring spot mosaic disease in the whole growth stage.

IV. Prevention and control methods. At present, there is no radical cure method, only comprehensive preventive measures based on cultivation measures can be taken. 1. Selection of disease-resistant varieties. 2. Strengthen cultivation and management, improve cultivation and management measures of papaya, and enhance plant resistance and tolerance. 3. Remove diseased plants in time. 4. Eliminate the source of disease and isolate it properly. 5. Insecticides kill aphids. Spray regularly to kill aphids, check and spray in time at the peak of aphid migration, especially in dry season. Aphids like to perch around papaya garden weeds, pay attention to remove.