A Detailed Guide to the Latest Control Methods for Watermelon Fusarium Wilt
Watermelon fusarium wilt, commonly known as "dead vine disease," can occur at all stages of watermelon growth, with the most severe incidence during the fruiting stage. The optimal temperature for the pathogen is 25-30°C; when soil temperature is below 23°C or above 34°C, incidence is milder. When soil moisture content is high and humidity is great, incidence is severe. Planting disease-resistant watermelon varieties is the preferred measure for controlling this disease. Let's take a look together at the control methods for watermelon fusarium wilt!
Damage Symptoms
When seedlings are affected, they show damping-off symptoms. After transplanting, the lower leaves wilt, followed by the entire plant's leaves all withering and dying. The stem base becomes constricted, with brown lesions appearing, and sometimes an amber-colored gelatinous substance exudes from the diseased area, on which white mold layers and pale pink sticky material (conidia) form. The vascular bundles of the stem turn brown, sometimes with longitudinal cracks appearing. The roots turn brown and rot together with the stem.
Causes of Occurrence
The watermelon fusarium wilt pathogen mainly invades through root wounds or intercellular spaces at the tips of root hairs. It first grows between and within the host's parenchyma cells, then enters the vascular bundles and develops within the vessels. The pathogen secretes pectinase and cellulase, decomposing and destroying cells, causing pectin-like substances to accumulate in the vessels, blocking them and affecting water transport, which causes plant wilting. It spreads through infected soil. With continuous cropping, the pathogen population in the soil is high, and the diseased plant rate can reach around 70%. Diseased plant residues, contaminated manure, and seeds can also transmit the disease.
Integrated Control
The most effective method for controlling watermelon fusarium wilt is grafting to replace the root system. Use Cucurbitaceae crops with high resistance to fusarium wilt, such as bottle gourd or Shintosa, as rootstock to graft watermelon varieties. As long as care is taken to completely remove the watermelon roots, and the graft union is not allowed to contact the soil when transplanting seedlings, watermelon fusarium wilt can be effectively prevented. For own-rooted watermelon seedlings that have not been grafted, adhere to the plant protection policy of "prevention first, integrated control," and carefully implement agricultural control, biological control, and other integrated control measures.
Agricultural Control
1. Variety selection: Planting disease-resistant watermelon varieties is the preferred measure, such as selecting Xinong No. 8, Fengkang No. 8, and other varieties.
2. Grafting cultivation: The watermelon fusarium wilt pathogen has difficulty infecting bottle gourd, calabash gourd, pumpkin, and other crops. Using these crops as rootstock for grafting to replace the root system is a relatively good approach to solving watermelon fusarium wilt.
3. Paddy-upland rotation: Watermelon fusarium wilt can survive in soil for 10 years, but in water it can only survive for just over 130 days. Therefore, paddy-upland rotation is the best method for preventing fusarium wilt.
4. Seed treatment: Soak seeds in a 2-4% bleaching powder solution for 30 minutes, then remove and rinse clean. This can kill fusarium wilt and anthracnose pathogens on the seed surface.
5. Soil control: For nutrient soil used in seedling cultivation, use pond soil, paddy field soil, or wall soil. Do not use soil from melon fields or vegetable gardens. Farmyard manure must be fully decomposed, and do not use farmyard manure containing diseased plant residues.