What are the control methods for perilla rust disease?
Perilla is an annual upright herbaceous plant. The stem is 0.3-2 m tall, green or purple, obtusely quadrangular, with four grooves, densely covered with long soft hairs. The leaves are broadly ovate or round, 7-13 cm long, 4.5-10 cm wide, with a short-pointed or abruptly pointed tip, a rounded or broadly wedge-shaped base, and coarse serrations along the margin above the base, membranous or herbaceous, green or purple on both surfaces, or purple only on the lower surface, sparsely covered with soft hairs on the upper surface and appressed soft hairs on the lower surface, with 7-8 pairs of lateral veins, those in the lower part slightly closer together, rising obliquely, slightly prominent on the upper surface and distinctly prominent on the lower surface, slightly lighter in color; the petiole is 3-5 cm long, dorsiventrally flattened, densely covered with long soft hairs.
Growth characteristics of perilla
Perilla is highly adaptable and not demanding about soil. It grows well in well-drained sandy loam, loam, and clay loam, and when cultivated in fertile soil in front of and behind houses, along ditches and field edges. The previous crop is best as vegetables. It can also be planted under young fruit tree plantations.
Temperature requirements of perilla
Requirements for environmental conditions: Perilla prefers a warm and humid climate. The seeds can germinate when the soil temperature is above 5°C, and the suitable germination temperature is 18-23°C. The seedling stage can tolerate low temperatures of 1-2°C. The plant grows slowly at lower temperatures. Growth is vigorous in summer. The suitable temperature during the flowering period is 22-28°C, with a relative humidity of 75%-80%. It is relatively moisture-tolerant and fairly waterlogging-tolerant, but not drought-tolerant, especially during the formation period of the product organs; if the air is too dry, the stems and leaves become coarse and hard, with more fiber and poor quality. It has a wide adaptability to soil and can also grow in relatively shady places.
How to control perilla rust disease?
Symptoms of perilla rust disease:
On the back of the leaves are scattered small yellow nearly round naked pustules, which are the uredinia of the pathogen. When the disease is severe, the number of lesions is very large and they cover the leaf back, but the leaves are not seen to wither; sometimes the uredinia on the leaf back can be seen to be almost white, which is caused by parasitism by Ramulariacoleospori Sacc., called a hyperparasitic fungus.
Pathogen of perilla rust disease: Coleosporium perillae Syd., called perilla sheath rust fungus, belonging to the Basidiomycota fungi. The uredinia are yellow-orange on the leaf back, scattered to grouped, round or oval, 0.2-0.5 mm in size, not powdery; the urediniospores are pale yellow, spherical to nearly spherical, densely covered with small spines on the surface, with a colorless wall about 1.5μm thick, 17-26×12-18 (μm) in size. The telial stage has not been seen.
Transmission route and disease conditions of perilla rust disease: The pathogen overwinters as teliospores on diseased residues. In the warm south, urediniospores can be produced year-round and spread through successive transmission, and sometimes the telial stage is not seen. High temperature and high humidity conditions easily induce the disease.
Control methods for perilla rust disease:
1) Clean the field, strengthen management, adopt formula fertilization techniques, and plant at an appropriate density.
2) At the early stage of the disease, spray 15% triadimefon wettable powder at 1000-1500 times dilution, or 50% carboxin emulsifiable concentrate at 800 times dilution, 50% sulfur suspension concentrate at 300 times dilution, 25% propiconazole emulsifiable concentrate at 3000 times dilution, 25% propiconazole emulsifiable concentrate at 4000 times dilution plus 15% triadimefon wettable powder at 2000 times dilution, 70% mancozeb wettable powder at 1000 times dilution plus 15% triadimefon wettable powder at 2000 times dilution, 30% solid lime sulfur mixture at 150 times dilution, or 12.5% diniconazole wettable powder at 4000-5000 times dilution, once every about 15 days, for 1 or 2 applications.