This two-page, 4-color publications profiles the fungal root rot and wilt diseases and symptoms of dry bean. These diseases include: fusarium root rot, rhizoctonia root rot, pythium root rot, fusariuim yellows, and white mold

Chaky, Jennifer L.

Giesler, Loren J.

Harveson, Robert M.

Watkins, John E.

English

DigitalCommons@University of Nebraska

University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Historical Materials from University of Nebraska-Lincoln Extension Extension 2005 EC05-1894 Dry Bean Disease Profiles II: Fungal Root Rot and Wilt Diseases Robert M. Harveson University of Nebraska - Lincoln, rharveson2@unl.edu John E. Watkins University of Nebraska - Lincoln, jwatkins1@unl.edu Loren J. Giesler University of Nebraska - Lincoln, lgiesler1@unl.edu Jennifer L. Chaky University of Nebraska - Lincoln Follow this and additional works at: https://digitalcommons.unl.edu/extensionhist  Part of the Agriculture Commons, and the Curriculum and Instruction Commons Harveson, Robert M.; Watkins, John E.; Giesler, Loren J.; and Chaky, Jennifer L., "EC05-1894 Dry Bean Disease Profiles II: Fungal Root Rot and Wilt Diseases" (2005). Historical Materials from University of Nebraska-Lincoln Extension. 1613. https://digitalcommons.unl.edu/extensionhist/1613 This Article is brought to you for free and open access by the Extension at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Historical Materials from University of Nebraska-Lincoln Extension by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. University of Nebraska Cooperative Extension EC05-1894Dry Bean Disease Profiles IIFungal Root Rot and Wilt DiseasesNebrli3la UNL Extension Plant PathologyTeamRobert M. Harveson,John E. \flatkins,LorenJ. Giesler, andJennifer L. ChakyLineohDibeases S5rmptoms*Fusarium root rotFusarium solanif. sp. phaseoliInitial symptoms appear as reddislu longitudinal streaks on hypocotylsand taproots (Figure 1a). Affected areas may merge and enlarge with age,turn necroti c (F igure 1b), and gradually extend up the stem (F igure 1 c).Plants are seldom killed and often compensate for severe infection by pro-ducing numerous adventitious roots above the rotted taproots (Figure Ld).Foliar symptoms often involve yellowing and stunting (Figure 1e). Stress-es sudr as dry conditions and soil compaction combined with disease alsolimit root growth and result in severely stunted plants (Figure 1fl.Rhizoctonia root rotRhizaetmia solaniDisease begins as small circular or linear sunken lesions with a reddish-brown border (Figure 2a). Cankers enlarge with age and may retard nor-mal plant growth by gtudling hypocotyls (Figure 2b).If rhe root systemis sufficiently destroyed" foliage completely collapses and plants neverrecover and die (Figure2c).Pythium root rotPythium spp.Pythium spp. can cause both pre- and postemergence damping off. In-fected seedlings that do emerge may wilt and die within several weeks(Figure 3a). Roots and hypocotyls may show lesions that are initiallywater-soaked and may continue to progress up stems several inchesabove the soil line (Figure 3b). This results in poorly functioning, necroticroot systems in the surviving plants. Disease incidence is often greater inlower areas of fields where water tends to accumulate (Figure 3c).Fusarium yellowsFusarium oxysporumf. sp. phaseoliFoliar symptoms first appear as yellowing and wilting of older leaves(Figure 4a), followed by younger leaves if the disease progresses. Severe-ly affected plants may wilt permanently. Factors favoring wilt are thesame as those for Fusarium root rot, including high temperature stressand soil compaction. Vascular discoloration of root tissues is the primarydiagnostic symptom (Figure 4b) and it varies in intensity depending oncultivar and environmental conditions.White moldS cler o tinia s clerotior umThe pathogen survives as hard, black sclerotia in soils or infected plantresidue (Figure Sa).The sclerotia germinate in soils to form mushroom-like apothecia (Figure 5b): These structures release spores, initiatinginfection. Infection is first seen as small water-soaked spots on stemgpods, or leaves. The spots enlarge to become a rotted" watery mass of tis-sue covered with white, moldy fungal growth. Affected plants wilt andentire branches or plants may be k'rlled (Figure 5c). Dead, infected plantsdry out and are bleached wlite (Figure 5d), which contrasts to the normallight tan color of mature bean plants. Masses of white mycelium developinto the sclerotia (Figure 5e) and serve as an overwintering mechanism toinitiate new inJections in later years.*Root rot diseases are difficult to correctly identi$r by symptoms exclusively and often need complete confirmation bylaboratory testsPhoto Credits: Figures 4a and 4b courtesy of H.F. Schwartz, Extension Specialist in Plant Pathology at Colorado State Uni-versity. All other photos courtesy of faculty in the University of Nebraska Institute of Agriculture and Natural Resources.University of Nebraska-Lincoln Extension educational programs abide with the non-discriminationpolicies of the University of Nebraska-Lincoln.Extension is a Division of the Institute of Agriculture and Natural Resources at the University ofNebraska-Lincoln cooperating with lhe Counties and the U.S. Department of Agricultvre.DUIA_NR

EC05-1894 Dry Bean Disease Profiles II: Fungal Root Rot and Wilt Diseases

UNL | Libraries

University of Nebraska - Lincoln 
DigitalCommons@University of Nebraska - Lincoln 
Historical Materials from University of 
Nebraska-Lincoln Extension Extension 
2005 
EC05-1894 Dry Bean Disease Profiles II: Fungal Root Rot and Wilt 
Diseases 
Robert M. Harveson 
University of Nebraska - Lincoln, rharveson2@unl.edu 
John E. Watkins 
University of Nebraska - Lincoln, jwatkins1@unl.edu 
Loren J. Giesler 
University of Nebraska - Lincoln, lgiesler1@unl.edu 
Jennifer L. Chaky 
University of Nebraska - Lincoln 
Follow this and additional works at: https://digitalcommons.unl.edu/extensionhist 
 Part of the Agriculture Commons, and the Curriculum and Instruction Commons 
Harveson, Robert M.; Watkins, John E.; Giesler, Loren J.; and Chaky, Jennifer L., "EC05-1894 Dry Bean 
Disease Profiles II: Fungal Root Rot and Wilt Diseases" (2005). Historical Materials from University of 
Nebraska-Lincoln Extension. 1613. 
https://digitalcommons.unl.edu/extensionhist/1613 
This Article is brought to you for free and open access by the Extension at DigitalCommons@University of Nebraska - 
Lincoln. It has been accepted for inclusion in Historical Materials from University of Nebraska-Lincoln Extension by an 
authorized administrator of DigitalCommons@University of Nebraska - Lincoln. 
University of Nebraska Cooperative Extension EC05-1894
Dry Bean Disease Profiles II
Fungal Root Rot and Wilt Diseases
Nebrli3la UNL Extension Plant PathologyTeamRobert M. Harveson,John E. \flatkins,
LorenJ. Giesler, andJennifer L. ChakyLineoh
Dibeases S5rmptoms*
Fusarium root rot
Fusarium solani
f. sp. phaseoli
Initial symptoms appear as reddislu longitudinal streaks on hypocotyls
and taproots (Figure 1a). Affected areas may merge and enlarge with age,
turn necroti c (F igure 1b), and gradually extend up the stem (F igure 1 c).
Plants are seldom killed and often compensate for severe infection by pro-
ducing numerous adventitious roots above the rotted taproots (Figure Ld).
Foliar symptoms often involve yellowing and stunting (Figure 1e). Stress-
es sudr as dry conditions and soil compaction combined with disease also
limit root growth and result in severely stunted plants (Figure 1fl.
Rhizoctonia root rot
Rhizaetmia solani
Disease begins as small circular or linear sunken lesions with a reddish-
brown border (Figure 2a). Cankers enlarge with age and may retard nor-
mal plant growth by gtudling hypocotyls (Figure 2b).If rhe root system
is sufficiently destroyed" foliage completely collapses and plants never
recover and die (Figure2c).
Pythium root rot
Pythium spp.
Pythium spp. can cause both pre- and postemergence damping off. In-
fected seedlings that do emerge may wilt and die within several weeks
(Figure 3a). Roots and hypocotyls may show lesions that are initially
water-soaked and may continue to progress up stems several inches
above the soil line (Figure 3b). This results in poorly functioning, necrotic
root systems in the surviving plants. Disease incidence is often greater in
lower areas of fields where water tends to accumulate (Figure 3c).
Fusarium yellows
Fusarium oxysporum
f. sp. phaseoli
Foliar symptoms first appear as yellowing and wilting of older leaves
(Figure 4a), followed by younger leaves if the disease progresses. Severe-
ly affected plants may wilt permanently. Factors favoring wilt are the
same as those for Fusarium root rot, including high temperature stress
and soil compaction. Vascular discoloration of root tissues is the primary
diagnostic symptom (Figure 4b) and it varies in intensity depending on
cultivar and environmental conditions.
White mold
S cler o tinia s clerotior um
The pathogen survives as hard, black sclerotia in soils or infected plant
residue (Figure Sa).The sclerotia germinate in soils to form mushroom-
like apothecia (Figure 5b): These structures release spores, initiating
infection. Infection is first seen as small water-soaked spots on stemg
pods, or leaves. The spots enlarge to become a rotted" watery mass of tis-
sue covered with white, moldy fungal growth. Affected plants wilt and
entire branches or plants may be k'rlled (Figure 5c). Dead, infected plants
dry out and are bleached wlite (Figure 5d), which contrasts to the normal
light tan color of mature bean plants. Masses of white mycelium develop
into the sclerotia (Figure 5e) and serve as an overwintering mechanism to
initiate new inJections in later years.
*Root rot diseases are difficult to correctly identi$r by symptoms exclusively and often need complete confirmation by
laboratory tests
Photo Credits: Figures 4a and 4b courtesy of H.F. Schwartz, Extension Specialist in Plant Pathology at Colorado State Uni-
versity. All other photos courtesy of faculty in the University of Nebraska Institute of Agriculture and Natural Resources.
University of Nebraska-Lincoln Extension educational programs abide with the non-discrimination
policies of the University of Nebraska-Lincoln.
Extension is a Division of the Institute of Agriculture and Natural Resources at the University of
Nebraska-Lincoln cooperating with lhe Counties and the U.S. Department of Agricultvre.
DU
IA_NR


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EC05-1894 Dry Bean Disease Profiles II: Fungal Root Rot and Wilt Diseases

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