Method for controlling watermelon anthracnose with difenoconazole-propiconazole

Watermelon anthracnose overwinters as mycelium or pseudosclerotia on diseased plant residues in the soil. The following year, when suitable conditions occur, it produces conidiophores and conidia, which land on plants or watermelons and cause infection. After watermelons become infected, the diseased parts again produce large amounts of conidia, which spread via rain, wind and irrigation water, causing repeated infection. Disease can occur at 10-30°C, and temperatures of 20-24°C with a relative humidity of 90.95% are suitable for its occurrence. When the temperature is above 28°C and the humidity is below 54%, the disease is mild or does not occur. Seed-borne bacteria can survive for 2 years; when infected seeds are sown, the cotyledons become infected after emergence. In low-lying areas with poor drainage, or where there is excessive nitrogen fertilizer, poor ventilation, or continuous cropping, the disease is severe. Watermelons harvested from severely diseased fields or after rain also develop the disease during storage and transport.

Chemical control methods for watermelon anthracnose

(1) Use disease-free seeds, or disinfect the seeds. Soak the seeds in 55°C warm water for 15 minutes, then cool them, or soak them in 150 times diluted 40% formalin for 30 minutes, then rinse them clean with clean water, and then place them in cold water to soak for 5 hours. Watermelon varieties differ in their sensitivity to formalin, so a test should be done first to avoid phytotoxicity. Alternatively, use 150 times diluted streptomycin sulfate and soak the seeds for 15 minutes. A 20% seed coating agent can also be used to coat the melon seeds.

(2) Select disease-resistant varieties. Currently, the varieties used in production are mostly resistant to race 1 and race 3, so attention should be paid to breeding varieties resistant to race 2.

(3) Carry out crop rotation with non-cucurbit crops for more than 3 years.

(4) Strengthen management, use formula fertilization, apply fully decomposed organic fertilizer, choose sandy soil, pay attention to leveling the land, prevent water accumulation, drain promptly after rain, plant at a reasonable density, and remove field weeds in time.

(5) For watermelons grown under protected cultivation, the smoke method or dust method can be used; for specific methods, see cucumber anthracnose.

(6) Chemical control. In protected cultivation and open fields, at the early stage of disease, spray 800 times diluted 50% thiophanate-methyl wettable powder plus 800 times diluted 75% chlorothalonil wettable powder, or mix and spray 800 times diluted 50% carbendazim wettable powder plus 800 times diluted 75% chlorothalonil wettable powder. In addition, 500 times diluted 36% thiophanate-methyl suspension concentrate, 800 times diluted 80% anthracnose thiram wettable powder, 200 times diluted 2% antimycin (120) aqueous solution, and 150 times diluted 2% wuyiencin aqueous solution can also be used, once every 7-10 days, for 2-3 consecutive treatments.

(7) Spray difenoconazole-propiconazole, which kills bacteria in 2-3 hours, controls the disease in 1-2 days, and has a long residual effect. Difenoconazole-propiconazole shows excellent therapeutic effects in controlling anthracnose and is a relatively ideal low-toxicity, high-efficiency fungicide; difenoconazole-propiconazole is even more effective in controlling anthracnose.