Chinese yam Cylindrosporium leaf spot

[Pathogen] The pathogen is a fungus belonging to the subphylum Hemiptera, Cyindrosporium dioscoreae Miyabe et S. Ito. Conidia disk grows on both sides of leaves, initially buried, aggregated or scattered, with a size of 200-250? M; Spore stem linear, long cylindrical, colorless, single celled, upright or slightly curved without branching, size (20-25)? M × (2-2.5)? M; Conidia needle shaped, with round or pointed ends, upright or slightly curved, single cell with round ends, without or with a few septa, colorless, transparent, and of size (37-40)? M × (2.5-3)? M.

Infection cycle

[Infection] Pathogens overwinter on the diseased residue using conidia or hyphae, becoming the source of infection at the beginning of the second year. After the onset of the disease, conidia are produced again. When suitable temperature and humidity conditions are met, after 1-2 days of incubation, the conidia can germinate and be re infected.

Occurring factors

The occurrence pattern is high humidity, frequent rainfall, and severe illness. The disease began to occur in mid to late July and became severe in August, continuing until harvest.

Prevention and control methods

[Prevention and Control]

(1) Seed treatment: Soak in 500 times solution of 50% carbendazim wettable powder for 30 minutes.

(2) Agricultural prevention and control. Crop rotation can effectively reduce or avoid the occurrence of diseases. After planting yam for 3 years, rotation is necessary. Crop rotation is better for crops in the Poaceae family. Choose sandy soil with high and dry terrain, fertile and loose soil, and good drainage for planting. Deep plowing before winter, using solar heat or film sealing to disinfect the soil. Cultivate in high ridges, deep ditches, and short rows, and pay attention to drainage during the rainy season. Do not apply immature fertilizers, apply more organic fertilizers, and increase the application of phosphorus and potassium fertilizers.

(3) Chemical prevention and control. Before the onset of the disease in late June, it is recommended to use 77% fungicidal wettable powder or 50% fipronil wettable powder 500 times liquid, or 70% mancozeb wettable powder 1000 times liquid, or 50% paracetamol wettable powder 1000-1500 times liquid. At the beginning of the onset of the disease, 12.5% imidazole wettable powder 2500 times solution, 70% methyl tobuzin wettable powder 1200 times solution, or 50% carbendazim wettable powder 500 times solution should be sprayed. Take turns using medication, usually requiring 4-6 sprays.

Source: World Agrochemical Network