Symptom Identification and Control Methods for Powdery Mildew on Kidney Beans

Kidney beans are suitable for cultivation in temperate and tropical high-altitude areas. They are relatively cold-tolerant and light-loving, belonging to cross-pollinated common beans and short-day crops. Kidney beans have a well-developed root system, green leaves that are alternate and heart-shaped, and flowers that are papilionaceous, arranged in racemes, with pedicels 15-18 cm long.

Growing environment of kidney beans

Common beans prefer warmth and cannot tolerate frost. The optimum temperature for seed germination is 20-25°C; germination is hindered below 8°C or above 35°C. The optimum temperature for seedling growth is 18-20°C; chilling injury occurs at 8°C. The optimum temperature for flowering and pod setting is 20-25°C; above 27°C or below 15°C, incomplete flowers easily develop, leading to flower and pod drop.

Common beans are short-day vegetables, but most varieties do not have strict requirements for day length and can be cultivated in all four seasons, hence the name "four-season beans." Varieties can be introduced between the north and south.

Common beans do not have strict requirements for soil quality, but they grow best in neutral loam with deep soil layers, good drainage, and rich organic matter. Common beans require more phosphorus and potassium, and also need nitrogen. During the seedling stage and bud stage, an adequate supply of nitrogen fertilizer is needed to ensure a high yield.

Common beans require moist conditions throughout the growing period. Due to their well-developed root system, they can tolerate a certain degree of drought, but they are especially sensitive to water deficiency or waterlogging during flowering and pod setting; excessive water can cause root rot.

Common beans are warmth-loving plants. The suitable temperature for growth is 15~25°C, and the optimum temperature for flowering and pod setting is 20~25°C. Low temperatures below 10°C or high temperatures above 30°C will affect growth and normal pollination and pod setting. They are short-day plants, but most varieties do not have strict requirements for day length; the cultivation season is mainly restricted by temperature.

Symptoms and control of powdery mildew on kidney beans

Symptoms of powdery mildew on kidney beans:

It mainly damages leaves, and stems, vines, and pods can also be affected. It causes premature aging of plants. When stems and pods are infected, small powdery spots appear, and in severe cases they cover the stems and pods, causing them to turn yellow and withered or even shrivel.

Control methods for powdery mildew on kidney beans:

① Seed disinfection: use 70% thiophanate-methyl wettable powder or 50% carbendazim plus 75% chlorothalonil wettable powder (1:1) to dress seeds (the dosage is 0.3%-0.4% of seed weight), and seal for 48-72 hours before sowing, which can delay the onset of disease by about 1 month;

② Strengthen management and cultivation; implement crop rotation where conditions permit; avoid planting in low-lying wet areas; use reasonable close planting, reasonably arrange bed orientation, improve drainage and irrigation systems, clear ditches to drain waterlogging after rain, use formula fertilization and especially increase the application of phosphorus and potassium fertilizers, avoid one-sided or excessive application of nitrogen fertilizer, and pay attention to field sanitation;

③ Spray pesticides in a timely manner to prevent and control the disease, prevent disease at the right time, and adhere to the principle of “treat early, prevent when few, treat thoroughly.” Also pay attention to mixed and rotational use, and spray evenly and sufficiently.