Main Pests and Diseases of Kidney Beans and Their Control Methods
See symptoms of southern blight of cucurbits: the stem base turns dark brown, densely covered with white filamentous mycelial strands, and later tea-brown round sclerotia form on the mycelial layer. Disease pattern and control methods: refer to southern blight of cucurbits. Distribution and host plants of sclerotinia rot of kidney bean: distributed in all regions. Besides damaging kidney beans, ...
See southern blight of cucurbits
Symptoms: the stem base turns dark brown, densely covered with white filamentous mycelial strands, and later tea-brown round sclerotia form on the mycelial layer.
Disease pattern and control methods: refer to southern blight of cucurbits
Sclerotinia rot of kidney bean
Distribution and host plants: distributed in all regions. Besides damaging kidney beans, it also infects other vegetables.
Symptoms: near the ground, the stem base or vine part first appears water-soaked, then turns grayish white. Under humid conditions, the affected stems are densely covered with white cottony mycelium and form black sclerotia.
Disease pattern: the sclerotia overwinter in the soil. Ascospores are carried by airflow for primary infection. During the growth period of the bean plants, secondary infection occurs mainly through mutual contact of mycelium. A temperature of about 20°C and a relative humidity above 85% favor the occurrence of the disease.
Control methods: (1) Crop rotation. (2) Strengthen field management, with rational fertilization and irrigation. (3) Spray promptly; the agents include 50% thiophanate-methyl wettable powder at 500 times dilution or 52% carbendazim wettable powder at 1000 times dilution, spraying once every 7-10 days, for a total of 2-3 times.
Bacterial blight of kidney bean
Distribution and host plants: occurs in the northeastern provinces, Henan, Hubei, Hunan, Jiangsu, Zhejiang and other provinces. It damages kidney beans and also infects mung beans, adzuki beans, cowpeas and hyacinth beans.
Symptoms: on the leaves, dark green water-soaked spots first appear; after expanding they become irregular in shape and turn brown, and the diseased tissue becomes thin and semi-transparent, surrounded by a yellow halo. Old lesions tend to rupture. Affected young leaves become deformed, and in severe cases the diseased leaves shrivel and drop off. The symptoms on stems and pods are similar to those on leaves: water-soaked spots first appear, and after expanding they appear as streak lesions (on stems) and round or irregularly shaped spots (on pods); the diseased parts are sunken and reddish brown. The spot surface often exudes pale yellow bacterial ooze. On diseased pods, the surface of the seed at the infected site shows yellow spots, or only the hilum shows slight yellow spotting.
Disease pattern: the pathogen overwinters inside seeds and on the ground with diseased plant residues. After infected seeds germinate, the cotyledons become diseased first and produce pathogenic bacteria, which spread to the bean plants through wind and rain, insects, humans and livestock, etc., and invade through stomata. High temperature and high humidity favor the epidemic of this disease, but at 36°C the disease gradually stops. Under high temperature, the incubation period is generally 2-3 days.
Control methods: (1) Select disease-free seeds for sowing. (2) Rotate with non-leguminous crops for two years. (3) Spray 0.5% Bordeaux mixture, once every 7-10 days, for a total of 2-3 times.
Mosaic disease of kidney bean
Distribution and host plants: distributed in all regions. There are three viruses causing kidney bean mosaic disease: besides damaging kidney beans, bean common mosaic virus also damages some Phaseolus plants, broad beans, cowpeas and hyacinth beans, etc. Bean yellow mosaic virus, besides including the host plants of bean common mosaic virus, also affects peas, soybeans, two species of clover, white hyacinth bean, white sweet clover, black alfalfa, gladiolus, etc. The kidney bean strain of cucumber mosaic virus only damages kidney beans.
Symptoms: young leaves first show vein clearing, chlorosis or stiff wrinkling, and newly grown young leaves show mosaic, with the green parts raised or sunken in a bag-like manner; some varieties become deformed after infection. Diseased plants are stunted or normal, and pods are generally normal. The symptoms caused by bean yellow mosaic virus are more severe than those caused by other strains, the mosaic color is more yellow, and the downward curling of leaves is also more severe.
Disease pattern: the source of primary infection is mainly overwintering host plants; besides bean yellow mosaic virus, the virus-carrying seeds of the other two viruses are also major sources of primary infection. During the growth period, transmission occurs mainly through aphids. The time required for aphids to acquire the virus on diseased plants and to transmit the virus to healthy plants is about 1-5 minutes, but for bean yellow mosaic the minimum times are 15 seconds and 15-30 seconds respectively. Under high temperature (26°C), severe mosaic, dwarfing and leaf curling mostly appear; at about 18°C, mild mosaic appears; above 28°C and below 18°C, symptoms are suppressed; strong light and prolonged light duration tend to aggravate the symptoms.
Control methods: (1) Select and breed disease-resistant varieties. (2) Save seeds from disease-free plants. (3) Control aphids promptly.