Lentil Disease Diagnostic Series
(PP1913, Jan. 2019)
A continuation of the Disease diagnostic series cards, these are funded externally and will be distributed to growers and other stakeholders.
Julie Pasche, Dry Bean and Pulse Crop Pathologist, North Dakota State University
Audrey Kalil, Plant Pathologist, Williston Research Extension Center, North Dakota State University; Samuel Markell, Extension Plant Pathologist, North Dakota State University
Availability: Web only
- Contents
Pythium seed and seedling rot
Pythium ultimum, P. irregulare, P. aphanidermatum and other Pythium species
FIGURE 1 – Brown/black discoloration and pruning of lateral and tap roots by Pythium irregulare
Photos: T. Paulitz, USDA-ARS, Pullman, Wash.
FIGURE 2 – Range of yellowing on plant foliage
Photo: T. Paulitz, USDA-ARS, Pullman, Wash.
AUTHORS:Lyndon Porter, Timothy Paulitz and Kurt Schroeder
SYMPTOMS
• Poor emergence, rotted seed with light brown root discoloration
• Stunted plants with yellow or purple leaves developing from the bottom
FACTORS FAVORING DEVELOPMENT
• Cool, water-saturated or compacted soil and poor seed vigor
IMPORTANT FACTS
• Metalaxyl (mefenoxam)-resistant Pythium is present in some growing regions
• Effective seed treatments are available for metalaxyl-resistant and sensitive Pythium
• Avoid planting into wet or compacted soils
• Pathogen survives on plant debris and in soil
• Resistant varieties are not available
• Often occurs in complex with other root rots
• Can be confused with other root rots and water logging
Fusarium root rot
Fusarium avenaceum and other Fusarium species
FIGURE 1 – Brown to reddish-brown lesions on lower stems and roots caused by Fusarium infection
Photo: K. Zitnick-Anderson, NDSU
FIGURE 2 – Infected seedlings
Photo: K. Zitnick-Anderson, NDSU
FIGURE 3 – Yellowing progressing upward and premature death caused by F. avenaceum (diseased [middle/bottom] and healthy [top] roots)
Photo: L. Porter, USDA-ARS, Prosser, Wash.
AUTHORS: Audrey Kalil and Lyndon Porter
SYMPTOMS
• Poor emergence
• Wilting, stunting and premature death
FACTORS FAVORING DEVELOPMENT
• Soil compaction and plant stress
• Warm, moist soil (68 to 82 F)
• Short pea and lentil rotations
IMPORTANT FACTS
• Pathogen survives on plant debris and in soil
• Often occurs in complex with other root diseases
• Resistant varieties are not available
• Fungicide seed treatments may be recommended
• Can be confused with other root rots and water logging
Rhizoctonia seed, seedling and root rot
Rhizoctonia solani
FIGURE 1 – Sunken brown lesions on stem and root just below soil
Photo: K. Zitnick-Anderson, NDSU
FIGURE 2 – Moderate (top) to severe (bottom) Rhizoctonia root rot
Photo: K. Zitnick-Anderson, NDSU
AUTHORS: Jessica Rupp, Myron Bruce and Timothy Paulitz
SYMPTOMS
• Poor emergence
• Reddish-brown to dark brown lesions on roots and base of stem
• Secondary roots absent
• Plants are stunted and leaves turn yellow
FACTORS FAVORING DEVELOPMENT
• Wet, compacted or waterlogged soils
IMPORTANT FACTS
• Pathogen survives on plant debris and in soil
• Resistant varieties are not available
• Fungicide seed treatments may be recommended
• Often occurs in a complex with other root rots
• Can be confused with other root rots and water logging
Aphanomyces root rot
Aphanomyces euteiches
FIGURE 1 – Infected roots with caramel-brown root rot (R), compared with healthy roots (L)
Photo: L. Porter, USDA-ARS, Prosser, Wash.
FIGURE 2 – Infection moving up primary stem
Photo: L. Porter, USDA-ARS, Prosser, Wash.
AUTHORS: Lyndon Porter
SYMPTOMS
• Root rot may extend slightly above the soil line
• Leaf yellowing progresses from lower canopy upward
• Early season stunting and premature plant death
FACTORS FAVORING DEVELOPMENT
• Cool, wet spring conditions
• High soil moisture
• Short rotations with peas and lentils
IMPORTANT FACTS
• Chickpea, cereals and faba bean are not important hosts
• Often occurs in a complex with other root rot diseases
• Can survive for many (20) years in soil without a susceptible host
• Seed treatments and genetic resistance are not effective
• Can be confused with other root rots and water logging
Anthracnose
Colletotrichum species
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FIGURE 1 – Small black fungal resting structures (microsclerotia) within anthracnose lesions
Photo: Michael Wunsch, NDSU
FIGURE 2 – Severe anthracnose lesions coalescing
Photo: Michael Wunsch, NDSU
FIGURE 3 – Anthracnose-infected pods and discolored seeds
Photo: Michael Wunsch, NDSU
AUTHORS: Michael Wunsch and Julie Pasche
SYMPTOMS
• Light-brown stem lesions with a dark border
• Symptoms initiate at the base of plant and spread upward
• Patches of dead plants develop when stem lesions girdle plant
FACTORS FAVORING DEVELOPMENT
• Abundant rainfall during bloom and pod development
• Wide range of temperatures; 68 to 74 F optimal
• Dense canopy
IMPORTANT FACTS
• Seed quality declines with increasing anthracnose severity
• Varieties differ in susceptibility to anthracnose; none are resistant
• No-till increases degradation of pathogen resting structures
• Commonly confused with Ascochyta blight
Ascochyta blight
Ascochyta lentis
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FIGURE 1 – Concentric ring pattern from pycnidia inside the light brown lesion
Photo: Michael Wunsch, NDSU
FIGURE 2 – Mid-canopy Ascochyta blight lesions
Photo: Michael Wunsch, NDSU
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FIGURE 3 – Discolored seeds produced in pods with Ascochtya lesions
Photos: Michael Wunsch, NDSU
AUTHORS:Michael Wunsch and Julie Pasche
SYMPTOMS
• Light brown leaf, stem and pod lesions with dark brown borders
• Small brown fungal fruiting structures (pycnidia) within lesions
• Disease lesions and/or picnidia within lesions often exhibit a concentric ring pattern (unlike anthracnose)
• Flower and pod abortion
FACTORS FAVORING DEVELOPMENT
• Cool, wet weather; 50 to 68 F optimal
• Planting lentils immediately adjacent to a field where Ascochyta blight occurred on lentils the previous year
IMPORTANT FACTS
• Ascochyta blight is seed-borne and seed-transmitted; seed should be tested
• Managed with crop rotation (minimum two years out of lentils) and foliar fungicides
• Commonly confused with anthracnose
Botrytis gray mold
Botrytis cinerea, B. fabae
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FIGURE 1 – Gray sporulation on diseased tissues when relative humidity is high
Photo: Michael Wunsch, NDSU
FIGURE 2 – Dead patches in lentil field
Photos: Michael Wunsch, NDSU
AUTHORS:Michael Wunsch and Julie Pasche
SYMPTOMS
• Gray fungal growth on diseased stems, leaves and pods in the lower canopy
• Plant tissue is light brown to bleached
• Plants become chlorotic, wilt and die when lesions girdle the lower stem
• Plant-to-plant spread of Botrytis is common, resulting in dead patches
FACTORS FAVORING DEVELOPMENT
• Dense crop canopies that restrict airflow
• High relative humidity and frequent rainfall
• Cool temperatures; 59 to 77 F optimal
IMPORTANT FACTS
• Resistant varieties are not available
• Fungicides can be effective if applied preventatively
• Commonly confused with white mold and anthracnose
Stemphylium blight
Stemphylium botryosum
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FIGURE 1 – Tan to light brown lesions at disease onset
Photos: Michael Wunsch, NDSU
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FIGURE 2 – Diseased leaflets that have become dark brown to gray due to pathogen sporulation under high relative humidity
Photos: Michael Wunsch, NDSU
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FIGURE 3 – Defoliated plants that have shed diseased leaves
Photos: Michael Wunsch, NDSU
AUTHORS:Weidong Chen and Michael Wunsch
SYMPTOMS
• Leaflets may exhibit angular lesions at disease onset
• Disease is most severe on leaves but also infects pods, stems and petioles
FACTORS FAVORING DEVELOPMENT
• Extended periods of high relative humidity in the last third of the growing season
• Warm temperatures; 77 to 86 F optimal
IMPORTANT FACTS
• Red lentils are generally more susceptible than green lentils
• Managed with fungicides and partially resistant varieties
• Can be confused with nutrient deficiencies (such as low nitrogen) or plant senescence
Bacterial blight
Pseudomonas syringae pv. syringae
FIGURE 1 – Brown, circular and translucent foliar lesions
Photo: F. Mathew, South Dakota State University
FIGURE 2 – Bacterial ooze from pod lesions
Photo: R. Harveson, University of Nebraska
AUTHORS:Febina Mathew, Bob Harveson and Bright Agindotan
SYMPTOMS
• Lesions observed on all above-ground plant parts
• Initial lesions are water-soaked and become necrotic through time
• Bacteria may ooze from lesions under high-humidity conditions
FACTORS FAVORING DEVELOPMENT
• Warm temperatures
• High humidity or moisture on leaves
• Hail
IMPORTANT FACTS
• Bacteria can be spread by rain, wind and mechanical means
• P. syringae pv. syringae can cause disease on soybean, dry edible beans and other legumes
• Physical damage (such as hail) can facilitate infection and spread
• Fungicides are not effective
• Planting infected seed can increase disease risk
• Can be confused with Ascochyta blight or anthracnose
Powdery mildew
Erysiphe pisi and Leveillula taurica
FIGURE 1 – Early infection - white “powdery” spots
Photo: L. Porter, USDA-ARS, Prosser, Wash.
FIGURE 2 – Leaf and stem surfaces covered with powdery mildew
Photo: L. Porter, USDA-ARS, Prosser, Wash.
FIGURE 3 – Feltlike white fungal growth
W. Chen, USDA-ARS, Pullman, Wash.
AUTHORS:Lyndon Porter and Weidong Chen
SYMPTOMS
• Most visible starting at flowering and later in the season
• Infected leaves can become chlorotic/necrotic and curled
• Infection begins as small spots that enlarge quickly and cover plant surfaces
FACTORS FAVORING DEVELOPMENT
• Late planting
• Conditions limiting sunlight
• Temperatures of 59 to 77 F are optimal
IMPORTANT FACTS
• Pathogen can be soil-borne, seed-borne and wind-dispersed
• Fungicides may be effective if applied early in disease development
• Crop rotation is important
• Lentil varieties have differing levels of resistance
• Can be confused with white mold and the fungal growth of saprophytes or other pathogens
White mold (Sclerotinia stem rot)
Sclerotinia sclerotiorum
FIGURE 1 – Dead patches of plants
Photo: W. Chen, USDA-ARS, Pullman, Wash.
FIGURE 2 – White, fluffy fungal growth on leaves and stems
Photo: L. Dighans, Pro Co-op Ag Center, Scobey, Mont.
FIGURE 3 – Bleached lesions with white fungal growth
Photo: W. Chen, USDA-ARS, Pullman, Wash.
FIGURE 4 – Dark, hard fungal structures (sclerotia) on the soil surface
Photo: W. Chen, USDA-ARS, Pullman, Wash.
AUTHORS:Mary Burrows, Weidong Chen and Michael Wunsch
SYMPTOMS
• First observed as water-soaked lesions
• Lesions enlarge and become bleached
• White fluffy fungal growth may appear under high humidity
• Hard, black sclerotia may appear late in the season
• Wilting
FACTORS FAVORING DEVELOPMENT
• Cool, wet conditions after canopy closure
• Short rotations with susceptible crops
• Lush canopy
IMPORTANT FACTS
• Sclerotia survive in the soil for several years
• Pathogen infects most broadleaf plants
• Fungicides can be effective if applied preventatively
• Can be confused with powdery mildew, nutrient deficiencies (low nitrogen) or plant senescence
Pea enation mosaic
Pea enation mosaic virus (PEMV)
FIGURE 1 – Twisted and malformed leaves
Photo: W. Chen, USDA-ARS, Pullman, Wash.
FIGURE 2 – Leaf mottling
Photo: W. Chen, USDA-ARS, Pullman, Wash.
FIGURE 3 – Leaf mottling
Photo: W. Chen, USDA-ARS, Pullman, Wash.
AUTHORS:Lyndon Porter, Bright Agindotan and Kevin McPhee
SYMPTOMS
• Small, circular to elongated translucent spots or streaks on leaves
• Vein clearing
• Stunted growth and malformed pods
FACTORS FAVORING DEVELOPMENT
• Presence of aphid vectors, including pea, cowpea, green peach, potato or foxglove
• Movement of aphids from virus-infected overwintering hosts in the spring or alfalfa fields during cuttings
IMPORTANT FACTS
• Can infect chickpea, pea, faba bean, vetch, crimson clover and lambsquarters
• PEMV is not seed-transmitted
• No known resistant varieties
• Insecticides applied to manage aphid vector may help reduce secondary spread
• Can be confused with other viruses or damage from herbicides or thrips
Bean leaf roll
Bean leaf roll virus (BLRV)
FIGURE 1 – Early leaf yellowing symptoms
Photo: B. Agindotan, Montana State University, Bozeman
FIGURE 2 – Advanced stage of yellowing (Infected [L, R] and healthy [C])
Photo: B. Agindotan, Montana State University, Bozeman
AUTHORS: Bright Agindotan and Lyndon Porter
SYMPTOMS
• Yellowing and stunting
• Small leaves
FACTORS FAVORING DEVELOPMENT
• Presence of other BLRV-infected legume crops and weeds
• Presence of aphid vectors, including pea, cowpea, potato and vetch
• Movement of aphids from alfalfa fields during cuttings
IMPORTANT FACTS
• Leaf rolling absent
• BLRV is not seed-transmitted
• BLRV infects pea, chickpea, lentil, alfalfa and other legumes
• Insecticides applied to manage aphid vectors may help reduce secondary spread
• Resistant varieties may be available
• Can be confused with nutrient deficiencies (low nitrogen) or plant senescence
January 2019
