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Dry Edible Bean Disease Diagnostic Series (PP1820)

This publication is a pictorial guide of Dry Edible Bean diseases.

Samuel Markell, Extension Plant Pathologist, North Dakota State University

Robert Harveson, Extension Plant Pathologist, University of Nebraska; Julie Pasche, Dry Bean and Pulse Crop Pathologist, North Dakota State University


Root Diseases

Fusarium root rot

Fusarium solani

 Figure 1 Photo by J Pasche, NDSU

FIGURE 1 – Susceptible (L) and moderately resistant (R) bean varieties under heavy Fusarium root rot pressure
Photo: R. Harveson, Univ. of Nebraska

Figure 2, Photo by Harveson, U of NE

FIGURE 2 – Reddish-brown lesions on hypocotyl and roots
Photo: R. Harveson, Univ. of Nebraska
Figure 3, Photo by Twedt, NDSU
FIGURE 3 – Split stems with a range of internal symptom severity
Photo: R. Harveson, Univ. of Nebraska

AUTHORS: Jessica Halvorson, Chryseis Tvedt, Julie Pasche, Bob Harveson and Sam Markell

SYMPTOMS

• Reddish-brown below-ground lesions
• Lesions may extend up the main root and hypocotyl
• Internal brown to red discoloration may be visible
• Yellow and stunted above-ground symptoms

FACTORS FAVORING DEVELOPMENT

• Cool and wet soils after planting
• Compacted soils and plant stress

IMPORTANT FACTS

• Soybeans and other pulse crops may be hosts
• May appear in circular patterns in a field
• Often found in a complex of other root rots
• Fungicide seed treatments may be effective early in the season
• Can be confused with other root rots and abiotic stresses

Pythium diseases

Pythium spp.

Figure 1Photo by Havereson, U of NE

FIGURE 1 – Water-soaking symptoms on roots and hypocotyls (R) and healthy root (L)
Photo: R. Harveson, Univ. of Nebraska

Figure 2Photo by Harveson, U of NE

FIGURE 2 – Wilting and death of a young bean plant
Photo: R. Harveson, Univ. of Nebraska

Photo by Harveson, U of NE

FIGURE 3 – Pythium blight-phase causing necrosis of stems and petioles
Photo: J. Pasche, NDSU

AUTHORS: Bob Harveson, Julie Pasche and Sam Markell

SYMPTOMS

• Initial root rot symptoms appear as elongated, water-soaked necrotic areas on roots or hypocotyls, sometimes extending above soil line
• Wilting and death of plants (damping off)
• Symptoms on above-ground tissues (blight phase) may occur after extended conditions of rain, irrigation, high humidity or high moisture

FACTORS FAVORING DEVELOPMENT

• High levels of soil moisture
• Disease incidence often is greater where water accumulates in fields

IMPORTANT FACTS

• Cool-weather species (most active below 75 F) include P. ultimum, while warm-weather species (80 to 95 F) include P. myriotylum and P. aphanidermatum
• The pathogens survive in soil for years and can be moved with soil
• Any area of the plant in contact with the soil may become infected, resulting in water-soaked areas of the stem or upper branches (blight-phase)
• Can be confused with other root rots, wilts and white mold (blight-phase only)

Rhizoctonia root rot

Rhizoctonia solani

Figure 1Photo by Harveson, U of NE

FIGURE 1 – Stunting, wilting and premature death
Photo: G. Yan. NDSU

Figure 2Photo by Harveson, U of NE

FIGURE 2 – Sunken reddish-brown cankers
Photo: R. Harveson, Univ. of Nebraska


Figure 3Photo by Pasche, NDSU

FIGURE 3 – Brick-red discoloration in pith
Photo: J. Pasche, NDSU

AUTHORS: Jessica Halvorson, Julie Pasche, Bob Harveson and Sam Markell

SYMPTOMS

• Stunting and premature death of plants in field
• Lesions or cankers with reddish-brown borders on roots and base of stem
• Internal brick-red discoloration of pith

FACTORS FAVORING DEVELOPMENT

• Moderate to high soil moisture
• Cool, compacted soil

IMPORTANT FACTS

• Soybeans, sugar beets, potatoes, pulse crops and some weeds are hosts
• Often found in a complex with other root rots
• Fungicide seed treatments may help manage disease early in the growing season
• Can be confused with other root rots and abiotic stresses

Soybean cyst nematode (SCN)

Heterodera glycines

Figure 1Photo by Yan, NDSU
FIGURE 1 – Yellow and stunted kidney beans with SCN
Photo: G. Yan. NDSU

Figure 2 InsertPhoto by Yan NDSU     Figure 2Photo by Yan, NDSU

FIGURE 2 – Small cream-colored females on dry bean roots
Photo: G. Yan, NDSU

Figure 3Photo Poromarto, NDSU

FIGURE 3 – Stunting of pinto bean growing in pots with different levels of SCN; no SCN (C); 5,000 eggs/100cc (L); 10,000 eggs/cc of SCN (R)
Photo: S Poromarto, NDSU

AUTHORS: Julie Pasche, Guiping Yan, Berlin Nelson, Sam Markell and Bob Harveson

SYMPTOMS

• Plants can be infected with no above-ground symptoms
• Stunted or yellow areas of the field
• Small (1/32 to 1/6 inch) cream-colored and lemon-shaped cysts on roots

FACTORS FAVORING DEVELOPMENT

• Rotation with soybeans
• Light soil texture
• High soil pH
• Warm and dry soil

IMPORTANT FACTS

• Soybeans and dry edible beans are hosts
• Dirty equipment, flooding and wind erosion are SCN dispersal mechanisms
• All market classes are hosts
• Research indicates that kidney beans are the market class most susceptible to SCN and black beans are the least susceptible

Soybean cyst nematode soil sampling

Heterodera glycines

 

Figure 1Courtesy Iowa State University

FIGURE 1 – High-risk spots for SCN
Courtesy Iowa State University

Figure 2Photo by Yan, NDSU

FIGURE 2 – SCN causing yellowing and stunting in kidney beans
Photo: G. Yan, NDSU

Figure 3Courtesy Iowa State University

FIGURE 3 – Counties positive for SCN (detected on soybeans) as of 2014
Courtesy Iowa State University

AUTHORS: Sam Markell, Guiping Yan, Berlin Nelson, Julie Pasche and Bob Harveson

WHY SOIL SAMPLE

• SCN is a microscopic worm that lives in the soil and parasitizes roots
• Soil sampling is the most reliable way to detect SCN

WHEN TO SAMPLE

• In late summer/fall (before or after harvest), when SCN population is highest and more easily detected

WHERE TO SAMPLE

• Anything that moves soil can move SCN
• Concentrate sampling in areas where SCN is likely to be introduced or develop, especially field entrances

HOW TO SAMPLE

• Aim for the roots, dig 6 to 8 inches deep, take 10 to 20 samples, mix and send to a lab

WHAT RESULTS MEAN

• Results are presented as eggs/100 cc, which is the number of nematode eggs in approximately 3.4 ounces of soil
• Low levels (for example, 50 or 100 eggs/100 cc) could be false positives and should be viewed with caution

Stem and Wilt Diseases

Bacterial wilt

Curtobacterium flaccumfaciens pv. flaccumfaciens

Figure 1Photo by Harveson,  U of NE
FIGURE 1 – Wilting and death of infected bean plants
Photo: R. Harveson, Univ. of Nebraska

Figure 2Photo by Harveson, U of NE

FIGURE 2 – Leaves with interveinal necrotic lesions surrounded by a wavy, yellow border
Photo: R. Harveson, Univ. of Nebraska

Figure 3Photo by Harveson, U of NE

FIGURE 3 – Shriveled, orange-stained seeds (bottom) and healthy seeds (top) obtained from the same infected plant
Photo: R. Harveson, Univ. of Nebraska

AUTHORS: Bob Harveson, Sam Markell and Julie Pasche

SYMPTOMS

• Leaf wilting during periods of warm, dry weather or periods of moisture stress
• Interveinal, necrotic lesions which may be surrounded by bright yellow borders
• Seeds from surviving infected plants often will shrivel and be stained yellow or orange

FACTORS FAVORING DEVELOPMENT

• Very hot air temperatures (greater than 90 F), with wet or humid conditions

IMPORTANT FACTS

• Wilt pathogen survives in bean residue or seeds from previous year
• Infected seeds are primary mechanism of long-distance movement
• Wet weather, hail, violent rain and windstorms help the pathogen spread within and between fields
• Can be confused with root rots and other bacterial pathogens; foliar symptoms of bacterial wilt tend to be more wavy or irregular than common bacterial blight lesions and do not include water-soaking

Fusarium yellows (wilt)

Fusarium oxysporum f. sp. phaseoli

Photo by Harveson, U of NE

FIGURE 1 – Yellowing and wilting of leaves
Photo: R. Harveson, Univ. of Nebraska

Figure 2Photo by Harveson, U of NE

FIGURE 2 – Permanent wilting and death of severely affected plants
Photo: R. Harveson, Univ. of Nebraska

Figure 3Phot by Schwartz, CO State U

FIGURE 3 – Vascular discoloration of plants affected by Fusarium wilt
Photo: R. Harveson, Univ. of Nebraska

AUTHORS: Bob Harveson, Sam Markell and Julie Pasche

SYMPTOMS

• Foliar symptoms first appear as yellowing and wilting of older leaves, followed by younger leaves if the disease progresses
• Severely affected plants may wilt permanently
• Vascular discoloration of roots and hypocotyl tissues is primary diagnostic symptom; degree of discoloration varies in intensity depending on cultivar and environmental conditions

FACTORS FAVORING DEVELOPMENT

• High temperature stress (greater than 86 F)
• Dry soil conditions
• Soil compaction

IMPORTANT FACTS

• Fusarium wilt often causes more dramatic symptoms than Fusarium root rot infections
• Unlike Fusarium root rot infections, Fusarium wilt seldom kills plants
• Death with wilt can occur before or after pod set
• Fusarium wilt can induce maturity two to three weeks earlier than normal
• Can be confused with other root rot and wilt diseases

Stem rot

Unknown sterile white basidiomycete (SWB)

Figure 1Photo, Harveson, U of NE

FIGURE 1 – Wilting symptoms characteristic of SWB infection
Photo: R. Harveson, Univ. of Nebraska

Figure 2Photo by Harveson, U of NE

FIGURE 2 – Small light brown lesions (L), moderate lesions (C) and large dark brown to black sunken lesions (R)
Photo: R. Harveson, Univ. of Nebraska

Figure 3Photo by Harveson, U of NE

FIGURE 3 – White mycelial strands of SWB and soil adhering to stems of infected plants
Photo: R. Harveson, Univ. of Nebraska

AUTHORS: Bob Harveson, Sam Markell and Julie Pasche

SYMPTOMS

• Wilting and death of young plants first observed after emergence
• On less severely affected plants, small lesions may be on hypocotyls
• Severe infection also can include sunken gray to black cankers on hypocotyls and stems
• White mycelial strands may grow over lesions or into stem piths; soil will adhere to stems when wilted plants are removed

FACTORS FAVORING DEVELOPMENT

• High soil temperatures, but has been reported to cause disease from 60 to 95 F

IMPORTANT FACTS

• Thought to have many hosts
• Can survive at least one year in soils, likely in colonized residue of weeds or other susceptible crops
• Can be confused with other root rots, wilts and white mold

White mold

Sclerotinia sclerotiorum

 Figure 1Photo by Markell, NDSU

FIGURE 1 – Small tan mushrooms (apothecia) about ¼ inch in diameter emerge from hard, black structures (sclerotia)
Photo: S. Markell, NDSU

Figure 2Photo by Wunsch, NDSU

FIGURE 2 – Enlarging tan lesions with white fungal growth
Photo: M. Wunsch, NDSU

Figure 3Photo by Markell, NDSU

FIGURE 3 – Mature stem lesion with dried-bone appearance, white fungal growth and black sclerotia
Photo: S. Markell, NDSU

Figure 4Photo by Harveson, U of NE

FIGURE 4 – Severe white mold damage
Photo: R. Harveson, Univ. of Nebraska

AUTHORS: Julie Pasche, Bob Harveson and Sam Markell

SYMPTOMS

• Water-soaked lesion that becomes tan as it enlarges
• Stem lesions will dry out, lighten in color and tissue may shred
• White fungal growth and hard black sclerotia may form in or on stem

FACTORS FAVORING DEVELOPMENT

• Wet soils prior to bloom; allows sclerotia to germinate and release spores
• Cool daytime temperatures (60 to 70F) during and after bloom
• Long periods of canopy wetness and/or frequent rainfall during bloom
• Lush plant growth

IMPORTANT FACTS

• All broadleaf crops and many weeds are susceptible to white mold
• Plants are only susceptible when in bloom
• Preventative fungicide applications may be economically viable
• Can be confused with wilt diseases or abiotic stress

Foliar Diseases

Anthracnose

Colletotrichum lindemuthianum

Figure 1Photo by Markell, NDSU
FIGURE 1 – Leaf lesions;
Figure 1 InsetPhoto, Markell, NDSU
Note sunken necrotic canker
Photos: S. Markell, NDSU
Figure 2Photo by Markell, NDSU
FIGURE 2 – Sunken circular pod lesions
Photo: S. Markell, NDSU
Figure 3Photo by Markell, NDSU
FIGURE 3 – White fungal growth and sunken lesions on discolored seed
Photo: S. Markell, NDSU

AUTHORS: Jessica Halvorson, Sam Markell, Julie Pasche and Bob Harveson

SYMPTOMS

• Can occur on all above-ground plant parts
• Leaf vein and petiole lesions are dark and slender
• Pod lesions begin as small brown spots, enlarge to become circular and sunken
• Infected seeds may appear discolored and have necrotic lesions
• White fungal growth or cream-salmon-colored spore masses may be visible in lesions

FACTORS FAVORING DEVELOPMENT

• Infected seed
• Cool (55 to 80 F) temperatures
• Frequent rain or thunderstorms

IMPORTANT FACTS

• Pathogen is seed-borne and wind-dispersed
• Spread can occur by splashing water
• Pathogen can spread by animals, people or machinery moving through fields when foliage is wet
• Planting certified disease-free seed is best way to prevent the disease
• Can be confused with bacterial blights

Bacterial brown spot

Pseudomonas syringae pv. syringae

Figure 1Photo by Harveson, U of NE
FIGURE 1 – Small circular necrotic lesions with yellow margins
Photo: R. Harveson, Univ. of Nebraska
Figure 2Photo by Harveson, U of NE
FIGURE 2 – Small necrotic lesions coalescing, forming large necrotic areas between veins
Photo: R. Harveson, Univ. of Nebraska

Figure 3Photo by Harveson, U of NE

FIGURE 3 – Older lesions with holes after necrotic tissues fell out
Photo: R. Harveson, Univ. of Nebraska

AUTHORS: Bob Harveson, Sam Markell and Julie Pasche

SYMPTOMS

• Small, circular, brown lesions, often surrounded by a narrow yellow zone (not always present)
• Lesions may coalesce to form linear necrotic streaks between leaf veins
• Centers of old lesions dry and fall out, leaving tattered strips or “shot holes”
• May infect leaves, pods and seeds

FACTORS FAVORING DEVELOPMENT

• Warm air temperatures (80 to 85 F) with wet or humid conditions
• Storms that damage plants (hail, high wind)
• Planting infected seeds favors early infection and disease spread

IMPORTANT FACTS

• Pathogen survives in seed, residue and on other living hosts
• Wet weather, hail, violent rain and windstorms spread the pathogen
• Can be confused with other bacterial blights: necrotic area is similar in size to halo blight but smaller than common bacterial blight; yellow margin (halo) is narrow and bright as with common blight, but halo blight’s is larger, faint

Bean common mosaic

Bean common mosaic virus (BCMV)

Figure 1Photo by Harveson, U of NE

FIGURE 1 – Mosaic, blistering and distortion (elongation) of leaves of affected plants
Photo: R. Harveson, Univ. of Nebraska

Figure 2Photo by Harveson, U of NE

FIGURE 2 – Vein banding of leaves on an infected plant
Photo: R. Harveson, Univ. of Nebraska

Figure 3Photo by Harveson, U of NE

FIGURE 3 – Blistering and downward cupping of rugose leaves of infected plant
Photo: R. Harveson, Univ. of Nebraska

AUTHORS: Bob Harveson, Julie Pasche and Sam Markell

SYMPTOMS

• Light and dark green mosaics and/or leaf malformation
• Downward rolling or cupping of leaves
• Vein banding, and stunting, necrosis or premature death

FACTORS FAVORING DEVELOPMENT

• Disease development dependent on susceptibility of cultivars and presence of aphids as vectors
• Yield losses more severe after early infections

IMPORTANT FACTS

• Type and severity of symptoms depend on host cultivar, virus strain and environment
• BCMV is spread among production areas by planting infected seed
• Several aphid species transmit BCMV
• More than 10 strains of BCMV are known
• Can be confused with other viruses, herbicide damage or plant stress

Common bean rust

Uromyces appendiculatus

Figure 1Photo by Harveson, U of NE
FIGURE 1 – Rust hot spot
Photo: R. Harveson, Univ. of Nebraska

Figure 2Photo by Markell, NDSU

FIGURE 2 – Cinnamon-brown (uredinia) and black (telia) rust pustules
Photo: S. Markell, NDSU

Figure 3Photo by Markell, NDSU

FIGURE 3 – Dusty cinnamon-brown spores rubbed off pustule with yellow halo
Photo: S. Markell, NDSU

AUTHORS: Sam Markell, Bob Harveson and Julie Pasche

SYMPTOMS

• Small (1/16 inch) cinnamon-brown pustules that may have a yellow halo
• Pustules turn black at end of growing season
• Usually first observed in areas of a field with concentrated infection, called “hot spots”

FACTORS FAVORING DEVELOPMENT

• Close proximity to a field that had rust the previous year
• Frequent heavy dews
• Moderate to warm temperatures (65 to 85 F)
• Factors favoring wet microclimates: lush plant growth, close to shelter belts, etc.

IMPORTANT FACTS

• Pathogen is specific to edible beans
• Infection may occur at any time and spread very quickly
• Fungicides applied after detection may be economically viable
• Pathogen has different races, which may overcome resistance
• Can be confused with soil splash, brown spot and halo blight

Common bacterial blight

Xanthomonas campestris pv. phaseoli

 Figure 1Photo by Markell, NDSU

FIGURE 1 – Large necrotic lesions with narrow yellow borders
Photo: S. Markell, NDSU

Figure 2Photo by Markell, NDSU

FIGURE 2 – Severely damaged leaves appearing burned or scorched
Photo: S. Markell, NDSU

 Figure 3Photo by Pasche, NDSU
Photo: J. Pasche, NDSU
FIGURE 3 – Infected pod
Figure 3 insertPhoto by Harveson, U of NE
Leaf and seeds
Photo: R. Harveson, Univ. of Nebraska    

AUTHORS: Bob Harveson, Julie Pasche and Sam Markell

SYMPTOMS

• Leaves, pods and seeds can be infected
• Initial symptoms: small water-soaked spots on the underside of leaves
• Spots enlarge and coalesce to form large necrotic areas with a narrow, bright yellow border
• Severely damaged leaves appear burned and remain attached at maturity

FACTORS FAVORING DEVELOPMENT

• Warm air temperatures (80 to 90 F) with wet or humid conditions
• Storms that damage plants (hail, high wind)
• Planting infected seeds favors early infection and disease spread

IMPORTANT FACTS

• Bacteria survive in fields on infected seed or bean tissues
• Pathogen can spread by animals, people or machinery moving through fields when foliage is wet
• Can be confused with anthracnose (pod infection) and bacterial diseases; yellow margin (halo) is similar in color and brightness to bacterial brown spot but necrotic area is larger

Halo blight

Pseudomonas syringae pv. phaseolicola

Figure 1Photo by Harveson, U of NE

FIGURE 1 – Small water-soaked spots on underside of leaf
Photo: R. Harveson, Univ. of Nebraska

Figure 2Photo by Pasche, NDSU

FIGURE 2 – Broad yellow-green halo surrounding small necrotic spot
Photo: J. Pasche, NDSU

Figure 3Photo by Harveson, U of NE

FIGURE 3 – Severe infection and the beginning of a systemic chlorosis in plants
Photo: R. Harveson, Univ. of Nebraska

AUTHORS: Bob Harveson, Julie Pasche and Sam Markell

SYMPTOMS

• Begins with small water-soaked spots that become necrotic
• Broad yellow-green halo may develop around necrotic spots
• In severe cases, a general systemic chlorosis may develop in infected plants
• Also may infect pods and seeds

FACTORS FAVORING DEVELOPMENT

• Cool air temperatures (68 to 72 F) with wet or humid conditions
• Planting infected seeds favors early infection and disease spread
• Storms with high winds, rain or hail will damage plants and spread pathogen from plant to plant

IMPORTANT FACTS

• Yellow-green chlorotic halo more pronounced at cool temperatures, less noticeable above 75 F
• Pathogen can spread by animals, people or machinery moving through fields when foliage is wet
• Can be confused with other bacterial blights; necrotic area is similar in size to bacterial brown spot but halo is much larger and a fainter yellow-green

 NDSU Extension Service     NDSU Experiment Station     U of NE

ND Bean Grower Assn            NE Drybean Commission            NOrth Central IPM Center

 

December 2016

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