What are the latest control methods for pepper powdery mildew?

Pepper powdery mildew mainly damages the leaves; both mature and young tender leaves can be affected. The pathogen is Leveillula taurica. During the vegetative growth stage, the hyphae are hidden inside the leaf tissue and only emerge on the leaf surface when reproductive bodies are produced, so it is often difficult to detect in the early stages. Once it is discovered, chemical control becomes difficult. Let us take a look together at how to control pepper powdery mildew!

Symptoms of pepper powdery mildew

Pepper powdery mildew mainly damages the leaves. Initially, round powdery mildew spots appear on the upper or lower surface of the leaves, gradually expanding and soon merging into one mass. In the late stage of the disease, the entire leaf is covered with white powder, which later turns grayish-white. Relatively speaking, the disease is more severe on the underside of the leaves. What is produced on the underside of pepper leaves is a white powdery substance, not a mold layer, and the lesions are densely distributed. In severe cases, the entire leaf turns yellow and drops off, seriously affecting the yield and quality of peppers.

Occurrence patterns of pepper powdery mildew

The pathogen overwinters as cleistothecia on diseased leaves on the soil surface. After overwintering, it produces conidia that spread through airflow. Generally, the disease occurs more frequently in the middle and late growth stages. In open fields, it is most likely to become epidemic from mid to late August to early September when the weather is dry. It takes about 20-plus hours from spore germination to infection, so the disease develops very rapidly and often becomes epidemic in a short period. The pathogen can be active at 10-30°C, with the optimum temperature being 20-25°C. The disease develops rapidly at 45-75% relative humidity. Conidia can still germinate and cause infection below 25%, while above 95% the disease is significantly suppressed.

How to control pepper powdery mildew?

1. For agricultural control of pepper powdery mildew, disease-resistant varieties can be selected, planting sites with higher terrain, good ventilation and good drainage should be chosen, phosphorus and potassium fertilizers should be applied more, and excessive nitrogen fertilizer should be avoided during the pepper growing period.

2. In the early stage of the disease, chemical control should be applied promptly. For chemical control, spray 25% ethirimol at 1000 times dilution, or 30% kresoxim-methyl aqueous solution at 1000-1500 times dilution, or 47% kasugamycin-copper oxychloride wettable powder at 600 times dilution. Spray once every 7-10 days, for 2-3 consecutive sprays.

3. When the disease is severe, 50% chloroisobromine cyanuric acid mixed with flusilazole can be sprayed in combination with ethirimol-azoxystrobin smoke agent for fumigating the greenhouse, with very good results. When using chemical prevention and control, attention should be paid to details such as spraying time, agent selection and reasonable water use to improve control efficacy.