Occurrence patterns and control methods of mint rust

Mintis a medicinal plant renowned at home and abroad, with the whole herb used as medicine. It is produced in Jiangsu. In recent years, with the adjustment of the rural planting structure and market demand, the planting area of mint in various parts of Jiangsu has expanded somewhat, but during its growth and development, it often suffers severe damage from rust, which not only causes serious yield reductions but also affects quality. The occurrence and control methods of mint rust are introduced below:

I. Symptom characteristics: Rust is a common and important disease of mint. It mainly damages leaves and stems. At the initial stage of the disease, yellow and orange-yellow slightly raised blister spots appear on the leaves or tender stems. Sometimes several blister spots merge into large spots. The epidermis of the blister spots ruptures, releasing yellow, orange-yellow or rust-colored powder (the pathogen's urediniospores). In the later stage of the disease, black powdery material (the pathogen's teliospores) grows on the diseased parts. The damaged leaves grow poorly at first, and because yellow spores adhere to the leaf surface, photosynthesis is seriously affected. In the later stage of the disease, most leaves dry up, causing early defoliation. After the tender stems are affected, the stems above the diseased part first wilt, and then the tender stems die. Mint rust also damages many medicinal plants such as Panax notoginseng, Corydalis yanhusuo, Atractylodes macrocephala, Angelica sinensis and Fritillaria.

II. Occurrence patterns: The pathogen overwinters as teliospores on diseased residues in the soil, and teliospores can also adhere to seeds to survive the winter. The following year, the teliospores germinate and cause damage. From late May to late June, if continuous rainy or dry weather occurs, the disease is extremely likely to develop, and it spreads quickly and causes severe damage. The urediniospores are spread by wind. The transmission distance is at least a few kilometers and at most dozens of kilometers. Therefore, once rust occurs, it often covers a wide range and a large area.

III. Control methods

1. Implement crop rotation. That is, carry out crop rotation for more than 3 years with crops that are not hosts of the rust pathogen.

2. Fertilize reasonably. During the growth period of mint, avoid applying too much nitrogen fertilizer, and appropriately increase the application of phosphorus and potassium fertilizers to promote steady plant growth and enhance disease resistance. At the same time, pay attention to field drainage to prevent waterlogging.

3. Chemical control. According to large-scale growers, spraying 1:1:100 Bordeaux mixture before the disease occurs has a good protective and preventive effect; when the disease occurs, spraying 25% triadimefon 1200-fold solution or 65% zineb 500-fold solution also has a very good effect. If the disease is severe, spray once every 10 days, with two consecutive treatments.