Bean diseases

Last updated: June 25, 2025

Major pathogens of bean diseases

Major bacterial pathogens of beans:

Corynebacterium flaccumfaciens pv. flaccumfaciens;
Pseudomonas syringae pv. syringae;
Xanthomonas phaseoli, X. campestris pv. phaseoli;
Xanthomonas phaseoli pv. fuscans;
Pseudomonas amygdali, P. syringae pv. @bio[phaseolicola.

Major fungal pathogens of bean diseases:

Alternaria spp.;
Isariopsis griseola;
Colletotrichum lindemuthianum, other Colletotrichum spp.;
Ascochyta spp.;
Mycosphaerella cruenta;
Phytophthora phaseoli;
Peronospora viciae;
Fusarium solani f. sp. phaseoli;
Fusarium oxysporum f. sp. phaseoli;
Botrytis cinerea;
Phyllosticta phaseolina;
Diaporthe phaseolorum;
Erysiphe betae;
Pythium spp., also Aphanomyces spp. and Thielaviopsis spp.;
Rhizoctonia solani;
Uromyces phaseoli, other Uromyces spp.;
Elsinoe phaseoli;
Colletotrichum truncatum;
Verticillium albo-atrum;
Sclerotinia sclerotiorum.

Viruses:

Bean common mosaic virus (Bean Common Mosaic Virus, BCMV);
Bean golden mosaic virus (Bean Golden Mosaic Virus, BGMV);
Bean pod mottle virus (Bean Pod Mottle Virus, BPMV);
Bean southern mosaic virus (Bean Southern Mosaic Virus, BSMV);
Bean yellow mosaic virus, bean strain (Bean Yellow Mosaic Virus, BYMV);
Cucumber mosaic virus, bean strain (Cucumber Mosaic Virus, CMV);
Sugar beet curly top virus (Sugar Beet Curly Top Virus, SBCTV);
Peanut stunt virus (Peanut Stunt Virus).

Root rots

Aphanomyces root rot

Aphanomyces root rot (English: Aphanomyces root rot) was not a problem for beans (Phaseolus sp.) until 1979, when a strain of Aphanomyces euteiches causing severe root rot was identified in Wisconsin (Pfender and Hagedorn, 1982). Since then it has been found in crops in several US states and Australia.

Infection can begin very early in the life of the plant or develop later, after the field soil is briefly waterlogged. The fungus affects the cortex of the root system, causing stunting and yellowing, after which the plant wilts and dies. Aphanomyces euteiches is often found together with Pythium sp., because the latter pathogen is more widespread, but it is favoured by similar conditions. The host range of Aphanomyces euteiches f. sp. phaseoli includes alfalfa, as well as snap beans and dry beans.

Some resistance has been found in breeding lines, but their agronomic characteristics are too far from commercial traits in the near future. Abundant irrigation is associated with infection, so soil moisture content and temperature are key factors in disease control in large-scale irrigated bean production. The use of green manure, especially mustard, has proved useful for suppressing Aphanomyces euteiches and other pathogens (Parke and Rand, 1989). Incorporation of brown mustard grown as a green manure, then chopped and rolled into the soil, has a fumigant effect on the pathogen. Other work has shown the value of other green manures together with an integrated approach to their control, using resistant varieties and proper soil management, to reduce the level of inoculum in the soil (Tu, 1991).

Fusarium root rot

Fusarium root rot of beans (English: Fusarium foot rot) occurs in most bean-growing areas worldwide. The disease usually causes the greatest damage when roots first encounter a stress situation caused by soil compaction, drought, waterlogging or oxygen stress. Early symptoms are stunting, chlorosis of upper leaves and reddening or browning at the base of the stem. Roots usually turn black, and the base of the stem may collapse. Sometimes symptoms may appear on short stretches of plants along a row when soil conditions cause stress.

Plant loss due to infection leads to reduced yield. Depending on the disease foci in the field, yield losses can be serious. Where plants are short, the efficiency of mechanized harvesting is reduced.

The pathogen Fusarium solani f. sp. phaseoli remains in the soil as chlamydospores for many years. Chlamydospores germinate in the presence of host root exudates and infect root tissues. Isolates of bean fusarium from the UK also proved pathogenic on roots of pea, but symptoms are not as severe as on beans (Phaseolus sp.).

Bean varieties differ in their degree of susceptibility to Fusarium root rot, but none is completely resistant. Some progress in developing resistance or tolerance has recently been achieved through research on root growth traits (Roman-Aviles et al., 2004), and this, together with soil management, will be the most practical form of control.

Rhizoctonia root rot

Rhizoctonia root rot (English: Rhizoctonia root rot) is widespread worldwide and is one of the most economically important diseases of bean roots and hypocotyls. Losses occur in all types of cultivation, whether ploughing and cultivation, minimum tillage or direct drilling. The disease often occurs in combination with Fusarium foot rot, but characteristic sunken reddish-edged lesions at the base of the stem are usually caused by Rhizoctonia solani. This disease usually occurs in warm weather and is not as much of a problem in Northern Europe as Fusarium solani.

Resistance to this disease is present in breeding lines, and some moderate resistance is present in commercial varieties; however, soil management is of paramount importance for minimizing risks and alleviating stresses on roots early in the growing season.

Southern blight (Sclerotinia rolfsii)

Southern blight (English: Southern blight) is serious in many tropical and subtropical regions of the world, where high temperatures and moist soil occur throughout the growing season. The causal agent is the fungus Sclerotinia rolfsii, which has a very wide host range among both monocotyledonous and dicotyledonous plants, including many vegetables. Early symptoms are similar to those of its relative Sclerotinia sclerotiorum, except that most of the infection continues just above and just below the soil surface, where the base of the stem is girdled and the plant dies. Sclerotia formed in the mycelium then serve as a source of inoculum for other hosts.

Deep cultivation with soil inversion buries sclerotia and limits contact between sclerotia and bean stems. Some resistant varieties are available, and some progress has been made in using biocontrol agents such as Trichoderma sp. and Gliocladium sp. as antagonists of the fungus.

White mould (Sclerotinia sclerotiorum)

White mould (English: white mould) occurs in most regions of the world except the tropics and affects a wide range of host crops. It is also a disease of peas, and much of what is used for peas is applicable to beans.

Pathogen: Sclerotinia sclerotiorum.

Infection occurs during periods of leaf wetness and optimal temperature; ascospores are released from apothecia, which in turn are formed from germinating sclerotia remaining in the soil after a previous infected crop (Boland and Hall, 1987; Phillips, 1994).

Infection leads to destruction of stem tissues and formation of dense white mycelium, which covers stems and leaves and infects pods. Large sclerotia form in infected tissue. The rate of spread of infection is rapid, and extensive losses of bean yield and quality occur. Cross-infection can also occur from harvested fresh bean pods to healthy bean pods in storage or packaging, further reducing marketability.

Some resistant varieties are known among breeding lines, but few are immune, and selecting varieties for resistance is difficult because plant architecture can also influence infection (Schwartz and Singh, 2013). Biocontrol agents such as Coniothyrium minitans have been used, which successfully reduce the number of sclerotia. The inoculant requires repeated application to establish populations, and often the interval between bean crops on a field is too long for the agent to survive.

Botrytis pod rot (Botrytis cinerea)

Botrytis pod rot, or grey mould (English: Botrytis pod rot (grey mould)), is widespread and present worldwide, infecting many agricultural crops and weeds during periods of high humidity.

Pathogen: Botrytis cinerea.

Infection occurs on the pod, usually after initial infection of wilted petals, which either stick to the pod after pod set or fall onto the leaf petiole, where the fungus can then infect the stem, causing girdling.

Botrytis is also a very important post-harvest disease of fresh beans. Pod damage leads to rejection of the snap bean crop for the fresh market or for processing. In dry beans, pods disintegrate and seeds may be exposed, leading to browning, and if seeds are also infected, the beans shatter.

Moist conditions are favourable for Botrytis cinerea, and the likelihood of a problem is higher if the weather is wet or if irrigation is excessive during flowering and pod set, allowing petals to remain attached to the ends of pods. A fungicide programme can be used, but in many cases the fungus has developed resistance to commonly used active ingredients.

Anthracnose (Colletotrichum lindemuthianum)

Anthracnose (English: Anthracnose) is distributed worldwide, but is more common in temperate and subtropical regions than in the tropics. It occurs in North and South America, as well as in Europe, Africa, Australia and Asia. It is one of the most important diseases, as it causes significant yield losses and damage from pod spoilage. The disease is seed-borne, and after spores appear in warm, moist conditions, spores spread very quickly with rain splashes to surrounding plants. The disease is especially harmful at the seedling emergence and pod formation stages.

Pathogen: the fungus Colletotrichum lindemuthianum (Sace, et Magn.) Br. et Cav.

Symptoms of infection are very characteristic: first, black or brown bordered leaf lesions appear, running along the leaf veins, as well as a browning effect. The affected tissue often falls out, forming so-called "shot holes". Later, pods become infected, on which deep round brownish-red coalescing sunken lesions form, black in the centre. In the depressions of the spots, especially in wet weather, whitish-orange or pink cushions of conidial sporulation of the fungus form. Conidia are colourless, oblong-cylindrical with rounded ends. Through the pod valves, the fungus infects seeds, on which the same spots form as on pods. On the cotyledons of seedlings, the disease appears as brown-red spots, with light centres. On stems and petioles, initially dash-like brown spots appear, later turning into cankers. In wet weather, reddish cushions—sporulation of the fungus—appear in the central part of the affected tissue.

The fungus persists as mycelium in affected plant residues and infected seeds. The disease is transmitted from plant to plant by raindrops. The optimal temperature for anthracnose development is about 20 °C. The incubation period of the disease is 3–7 days.

Some varieties are resistant to most races, but the pathogenicity of the fungus is very diverse. Seed coat infection can be controlled by fungicidal seed treatment, but despite the possibility of using foliar fungicides, the most effective means of control is prevention through the use of healthy seeds produced under dry conditions.

Bean rust (Uromyces appendiculatus)

Bean rust (English: Bean rust) occurs worldwide, but is most common in tropical and subtropical regions. In Latin America it is most serious in Brazil, the Caribbean, Central America and Mexico, as well as in Africa. In arid climates it occurs rarely, only under irrigation. Rust affects yield and pod quality for both the fresh vegetable market and dry bean production and can reduce dry bean yields by up to 30% through defoliation or reduction of leaf area.

Pathogen: obligate fungus Uromyces appendiculatus.

When pods become infected, the disease can cause deep dark cankers on the surface, making them unsuitable for sale on the fresh or processing market. Symptoms first appear as small round rust-coloured spots surrounded by a yellow halo. Pustules develop and produce orange-brown spores, which are transferred to surrounding leaves and plants by rain splashes or overhead irrigation. Later the spots become larger, and the spores turn black.

The pathogen persists as teliospores on plant residues. Mycelium on spurge rhizomes. In spring, teliospores germinate and form basidia with basidiospores, which infect broad beans and common beans. In heteroecious fungi, basidiospores infect spurge, on which the aecial stage develops, and then aeciospores infect the primary host.

There are a number of fungicides that are more effective when applied early in disease development. The most effective means of controlling bean rust is varietal resistance. Stable resistance is difficult because the pathogenic variability of the fungus is very great. Although most varieties are resistant to several rust races, only some have resistance to most local races. Many rust-resistance genes are present in common bean, and some have been used to create rust-resistant germplasm and varieties (Park et al., 2004). Significant progress has been made in the USA in breeding beans with multiple resistance genes.

Bacterial diseases

In all cases of bacterial diseases of beans, the primary source of infection is seed material, so strict phytosanitary procedures must be carried out in bean seed production areas. In dry areas, seed crops should be inspected during production and tested for bacterial pathogens. In some situations, streptomycin seed treatment is used to ensure surface sterilization, but it is not available in all countries.

Halo blight (Pseudomonas syringae)

Halo blight (English: halo blight) is a disease of temperate climates and is the most common of the seed-borne bacterial diseases of beans.

Pathogen: bacterium Pseudomonas syringae pv. phaseolicola.

Symptoms on leaves consist of small angular necrotic greasy spots, which are surrounded by a chlorotic area of tissue. Later, sunken, water-soaked greasy spots appear on pods, which penetrate into the pod wall until developing seeds become infected. Because the disease spreads easily during rain or overhead irrigation, the effect on the crop usually appears as small discrete spots that spread rapidly in the direction of the prevailing wind. Yield loss is caused by defoliation and plant death, and pod damage can lead to rejection of the crop when harvesting fresh beans.

The source of infection is infected seeds or crop residues, but under normal crop rotation the bacterium does not survive in the soil for more than 1 year.

There are no effective chemical control measures, so the only means of preventing the disease is seed health.

Common blight (Xanthomonas campestris)

Common bacterial blight (English: Common blight) affects leaves and pods and is considered a major problem in most tropical and semi-tropical bean-growing areas.

Pathogen: Xanthomonas campestris pv. phaseoli.

Symptoms of leaf damage appear as water-soaked spots that expand, and the surrounding tissue becomes necrotic and bordered by lemon-coloured tissue. Eventually the leaves take on a scalded appearance. Pod lesions are sunken and brown.

The disease can be very destructive during periods of warm, wet weather, when losses of yield and bean quality occur.

Bacterial wilt (Curtobacterium flaccumfaciens)

Bacterial wilt leads to wilting of bean plants during periods of moisture deficiency. It has been reported in the USA, Tunisia, Australia, Greece, Canada and Colombia, as well as in other production regions.

Pathogen: Curtobacterium flaccumfaciens.

Viruses

Schwartz et al. (2005) described a number of viral diseases associated with Phaseolus beans, but the most common serious viruses are bean common mosaic virus (BCMV), bean curly top virus (BCTV), bean yellow mosaic virus (BYMV) and cucumber mosaic virus (CMV).

Bean common mosaic virus (BCMV)

Bean common mosaic virus (English: Bean common mosaic virus, BCMV) occurs worldwide, and in areas where susceptible varieties are grown, the disease can cause serious yield losses, poor pod set and pod development. The virus can survive in weed hosts and to a small extent in infected seeds. The virus is then transmitted by vectors—aphids, including Acyrthosiphon pisum, Macrosiphon euphorbiaea, Myzus persicae and Aphis fabae. Pale and dark irregular areas appear on the trifoliate leaf surface, most often leaves curl downwards and may grow longer than the others. Some beans may develop brown colouration on leaf veins and stems. Most commercial varieties are resistant to BCMV, but dry bean varieties may be more susceptible. Effective aphid control and planting before aphid activity begins will also reduce the risk of infection.

Bean curly top virus (BCTV)

Bean curly top virus (English: Bean curly top virus, BCTV) occurs in the western USA and British Columbia. Seedlings develop as dwarf plants, with severe rugose and downward curling of leaves. Plants are severely dwarfed and bunchy. Leaves become brittle, and flowers may wilt. The virus has several hosts that are perennial or winter annual plants, such as Russian thistle (Salsola tragus), mustard, and sugar beet. The virus is transmitted by the beet leafhopper (Circulifer tenullus), and warm dry weather conditions early in the season promote migration of the virus from overwintering leafhopper hosts to newly emerged beans. There are a number of resistant varieties.

Bean yellow mosaic virus (BYMV)

Bean yellow mosaic virus (English: Bean yellow mosaic virus, BYMV) develops in beans at any time before flowering. Leaves may be wrinkled and pointed with some vein clearing. Leaves may droop, yellow speckling may appear on older leaves, and plants may be stunted. BYMV is widespread worldwide and has several leguminous and non-leguminous hosts. The virus is transmitted by aphids, and infection can occur on individual plants or in groups of plants. Depending on the degree of damage, yield may be reduced, and pods may be damaged or undersized. BYMV is also known as Phaseolus virus 2 and can be transmitted by seeds of some legumes, including Vicia faba. Several aphid vectors can transmit the virus between beans from overwintering hosts. The main vector is Acyrthosiphon pisum, the virus is persistent and has a wide host range, including pea, clover, alfalfa, gladiolus, freesia, lupin, soybean and wild legumes. Some resistant dry bean varieties exist, but early aphid control on flowering crops is the most effective means of preventing large-scale infection.

Cucumber mosaic virus (CMV)

Cucumber mosaic virus (English: Cucumber mosaic virus, CMV) occurs in many countries, including Europe and the Far East. In the USA, cases of whole bean fields being affected are known, but economic losses depend on the time of infection. With late infection, pod quality decreases.

Symptoms include narrowing and pointing of leaves with mosaic developing later. Other symptoms include leaf curling, green and chlorotic mottling, and dark green vein banding. Some CMV strains can be transmitted by bean seeds, but the disease is easily transmitted by several vectors—aphids. The virus has a wide range of weed hosts, including several perennial species.

Healthy seeds are a useful preventive measure, but aphid control is more important. Some commercial varieties are resistant to CMV, and work is currently underway to breed new varieties resistant to this virus.

References

Autko A.A. et al. (2012). Modern technologies in vegetable growing. Edited by Dr. of Agricultural Sciences A. A. Autko. National Academy of Sciences of Belarus, Institute of Vegetable Growing. Minsk: Belarusian Science.
Biddle, A. J. (2017). Peas and beans. Crop production science in horticulture. UK.