What are the control measures for watermelon viral disease?
Watermelon viral disease, also known as little leaf disease and mosaic disease, as the name implies, mainly damages the flowers and leaves. This disease occurs in all watermelon-growing areas of China, among which the northern melon-growing areas are mainly affected by the mosaic-type virus, while the southern melon-growing areas are mainly affected by the fern-leaf-type virus. Although the main parts damaged by this virus are the flowers and leaves, when the flowers and leaves are affected it can also cause the plants to be stunted, with poor flower development, and in severe cases it leads to poor fruit development, so that neither yield nor quality can be guaranteed, and it likewise affects the economic interests of growers. Here TheNaturePlanet introduces the control work related to watermelon viral disease, as well as matters related to what medicine to use after watermelons become diseased.
I. Damage symptoms of watermelon viral disease
As TheNaturePlanet mentioned earlier, the disease symptoms of watermelon viral disease differ between the north and south of China, with the fern-leaf-type virus in the south and the mosaic-type virus in the north. The symptoms of these two viruses are not completely the same, so here TheNaturePlanet will also introduce them separately.
Watermelon virus mainly shows two types of symptoms in the field: mosaic type and fern-leaf type. The first is the mosaic type: in the early stage, yellow-green mottled patterns appear on the top leaves, which later become wrinkled and deformed, with the leaves becoming smaller and the leaf surface uneven; the internodes of new stems and vines shorten, becoming slender and twisted, and fruit set is reduced or absent. The second is the fern-leaf type: new leaves become narrow and long, wrinkled and twisted, growth is slow, the plant is dwarfed, and sometimes the top shows clustered growth without elongating; flower development is poor, and in severe cases no fruit can be set. In diseased plants that develop symptoms later, the fruit develops poorly, forming deformed melons, and some have uneven fruit surfaces and small fruits, with the flesh dark brown, greatly affecting yield and quality.
II. Control methods for watermelon viral disease
1. Agricultural control
Select disease-resistant varieties. Select and keep seeds from disease-free plants. Seed treatment. Soak seeds in warm water at 55°C for 30 minutes, or soak them in a 10% trisodium phosphate solution for 20 minutes, then wash them clean with clear water before sprouting and sowing. Raise seedlings in a centralized manner, and lay silver-gray film in the field to repel aphids.
2. Chemical control
In the early stage of the disease, use 2% Junke Doke aqueous solution at 200-250 times dilution, or 20% Virus A wettable powder at 500 times dilution, or 1.5% Zhibingling emulsifiable concentrate at 1000 times dilution, or 30% Virus K wettable powder at 800 times dilution, or 20% Xiaoyedi at 1000 times dilution, etc., mixed with insecticides for aphid control, and spray for control. Apply once every 7 days, for 2-3 consecutive times. For fern-leaf-type symptoms, “Qibao 920” can be added, giving a good control effect.
3. Fertilization
Apply sufficient base fertilizer, carry out rational topdressing, increase potassium fertilizer application, water in time to prevent drought, and prune rationally to improve the disease resistance of the plants. Take care to remove weeds in and around the melon field, and pull out diseased plants in time. When carrying out field operations such as pruning and pollination, take care to minimize damage to the plants. Choose sunny days for removing side shoots and do it in the sunlight so that the wounds dry and shrink as quickly as possible. Eliminate aphids.
The above are the relevant control measures for watermelon viral disease. Here TheNaturePlanet reminds everyone that for the control of viral diseases, the principle of “prevention first, integrated control” should still be carried out. TheNaturePlanet has mentioned this principle many times, which also conforms to the needs of market development. Nowadays “pollution-free vegetables” are advocated, and naturally there is the same demand for fruit. If prevention is done well, the later use of pesticides for control will also be correspondingly reduced, and the watermelons grown will better meet consumers' requirements.