Title

Pea Disease Diagnostic Series

(PP1790 Revised, May 2025)
File
Summary

This series aids in disease identification.

Lead Author
Lead Author:
Samuel Markell, Extension Plant Pathologist North Dakota State University
Other Authors

Julie Pasche, Dry Bean and Pulse Crop Pathologist, North Dakota State University

Lyndon Porter, Research Plant Pathologist – Legumes, U.S. Department of Agriculture-Agricultural Research Service, Prosser, Wash.

Availability
Availability:
Web only
Publication Sections

Rots and Wilts

Fusarium root rot

AUTHORS: Julie S. Pasche, Lyndon Porter and Kimberly Zitnick-Anderson 

SYMPTOMS 
• Red to brown-black below-ground lesions 
• Lateral root reduction and complete destruction in severe infections 
• Below-ground red discolored vascular tissue is possible 
• Above-ground stunting, yellowing and necrosis 

Figure 1
Photo Credit:
L. Porter, USDA-ARS Prosser, WA
FIGURE 1 – Discrete lesions expanding from the point of seed attachment and coalescing into larger lesions
Figure 2
Photo Credit:
L. Porter, USDA-ARS Prosser, WA
FIGURE 2 – Advanced lesions affecting large areas of roots and hypocotyls
Figure 3
Photo Credit:
L. Porter, USDA-ARS Prosser, WA
FIGURE 3 – Infected plants yellowing from the base upward

FACTORS FAVORING DEVELOPMENT 
• Temperatures from 73 to 83 F and wet soils 
• Soil compaction and plant stress 
• Contaminated seed or plant debris IMPORTANT FACTS 
• Alternative hosts include dry beans, soybean, chickpea and lentil 
• Often seen in a complex with other root rots 
• Above-ground symptoms often not seen until flowering 
• Can be confused with other roo

Aphanomyces root rot

AUTHOR: Lyndon Porter 

SYMPTOMS 
• Caramel-brown root and below-ground stem 
• Outer root and below-ground stem tissue will slough off, exposing the vascular tissue 
• Lower leaves turn yellow; the plant may be stunted, wilt and/or die prematurely 

Figure 1
Photo Credit:
L. Porter, USDA-ARS Prosser, WA
FIGURE 1 – Caramel-brown infected roots (R) and healthy roots (L)
Figure 2
Photo Credit:
L. Porter, USDA-ARS Prosser, WA
FIGURE 2 – Infected roots and yellowing lower leaves

 

Figure 3
Photo Credit:
L. Porter, USDA-ARS Prosser, WA
FIGURE 3 – Outer root tissue sloughing off and exposing inner vascular tissue

FACTORS FAVORING DEVELOPMENT 
• Cool and wet spring conditions 
• Low-lying areas 
• Short rotations with peas or lentils 

IMPORTANT FACTS 
• Thick-walled spores can survive in soil for 20 years or more 
• Lentils are a host, but chickpeas and faba beans are not 
• Crop rotations of six or more years with nonhost can help reduce disease 
• Can be confused with other root rots and abiotic stress (water damage, etc.)

Pythium seed and seedling rot

AUTHOR: Lyndon Porter 

SYMPTOMS 
• Rotted seeds often are coated with soil that is difficult to remove, even with washing 
• Rotted tissue appears light brown 
• Stunted plants, poor vigor and pinching-off of secondary roots 

Figure 1
Photo Credit:
L. Porter, USDA-ARS Prosser, WA
FIGURE 1 – Light brown internal seed rot
Figure 2
Photo Credit:
L. Porter, USDA-ARS Prosser, WA
FIGURE 2 – Rotted seed coated with soil
Figure 3
Photo Credit:
L. Porter, USDA-ARS Prosser, WA
FIGURE 3 – Emerged plants with reduced vigor

FACTORS FAVORING DEVELOPMENT 
• Conditions that delay emergence, including planting into cool soils, poor seed vigor and compacted soils 

IMPORTANT FACTS 
• Common seed rot pathogen across the U.S. 
• Manage by maximizing speed of emergence by planting as shallow as possible in warm soils with high-quality seed 
• Fungicide seed treatments effective on Pythium should be used 
• Can be confused with water damage and other root rots 

Rhizoctonia seed, seedling and root rot

AUTHORS: Timothy Paulitz, Dipak Sharma-Poudyal, Lyndon Porter, Weidong Chen and Lindsey du Toit 

SYMPTOMS 
• Seeds may rot in soil, resulting in poor emergence 
• Seedlings have reddish-brown, sunken lesions on roots and base of stem 
• Pinching-off of tips of the main tap root and secondary roots 
• Plants become stunted and yellow 

Figure 1
Photo Credit:
L. Porter, USDA-ARS Prosser, WA
FIGURE 1 – Sunken brown lesions on below-ground stem tissue
Figure 2
Photo Credit:
L. Porter, USDA-ARS Prosser, WA
FIGURE 2 – Browning of the roots and pinching-off of root tips
Figure 3
Photo Credit:
L. Porter, USDA-ARS Prosser, WA
FIGURE 3 – Peas infected with Rhizoctoni

 

FACTORS FAVORING DEVELOPMENT 
• Wet, cool soils 
• Seed with poor germination IMPORTANT FACTS 
• Pathogen can survive in soil and plant debris 
• Rotation is largely ineffective and resistant cultivars are not available 
• Fungicide seed treatments are recommended 
• Can be confused with other root rots, water damage

Fusarium wilt

AUTHOR: Stephen Guy 

SYMPTOMS 
• Leaves curl and yellow progressively from the base of the plant upward, sometimes more severe on one side of the plant • Root vascular tissue is shades of yellow, orange or red, extending into the base of stem 
• Field distribution is scattered plants or concentrated patches 
• Plants may wilt 

Figure 1
Photo Credit:
S. Markell, NDSU
FIGURE 1 – Yellowing and curling of leaves
Figure 2
Photo Credit:
S. Guy, Washington State U
Figure 3
Photo Credit:
L. Porter, USDA-ARS Prosser, WA
FIGURE 3 – Orange-red vascular discoloration extending into the stem
Figure 4
Photo Credit:
S. Markell, NDSU
FIGURE 4 – Severe vascular discoloration

FACTORS FAVORING DEVELOPMENT 
• Previous history of disease in the field 
• Frequent cropping of susceptible varieties 
• Late planting IMPORTANT FACTS 
• Can survive in soil for 10 years or more 
• The fungus penetrates root tips and blocks vascular tissue 
• Pathogen has more than one race and resistant varieties may not be effective against all races 
• Can be confused with Aphanomyces and Fusarium root rots and abiotic stress

Spots and Lesions

Ascochyta blight

AUTHOR: Michael Wunsch 

SYMPTOMS 
• Leaf lesions are dark, irregular flecks and/or circular to oval lesions, with a concentric ring pattern 
• Purplish stem lesions develop at nodes, elongate and may girdle stem 
• Pod lesions are small, irregular to circular and brown to purplish black 
• Seed may be discolored 

Figure 1
Photo Credit:
M. Wunsch, NDSU
FIGURE 1 – Oval lesions with concentric rings
Figure 2
Photo Credit:
M. Wunsch, NDSU
FIGURE 2 – Irregular flecks on leaf, extending to petioles and stems
Figure 3
Photo Credit:
M. Wunsch, NDSU
FIGURE 3 – Small, irregular pod lesions
Figure 4
Photo Credit:
M. Wunsch, NDSU
FIGURE 4 – Stem lesions

FACTORS FAVORING DEVELOPMENT 
• Cool, wet weather 
• Short rotational intervals between pea crops 

IMPORTANT FACTS 
• Primarily residue-borne but can be seedborne 
• Crop rotation reduces but does not eliminate pathogen inoculum 
• The host range of the causal pathogens is limited to field peas 
• Can be confused with bacterial blight or Septoria blight

Bacterial blight and brown spot

AUTHOR: Robert M. Harveson 

SYMPTOMS 
• Symptoms occur on all above-ground plant parts 
• Lesions initially are water-soaked and later turn necrotic 
• Lesions are vein-delimited, angular in shape and translucent 
• Bacterial ooze may be seen under conditions of high humidity 
 

Figure 1
Photo Credit:
R. Harveson, Univ. of Nebraska
FIGURE 1 – Angular leaf lesions delimited by veins


 

Figure 2
Photo Credit:
R. Harveson, Univ. of Nebraska
FIGURE 2 – Watery stem lesions forming in linear patterns as disease progresses
Figure 3
Photo Credit:
R. Harveson, Univ. of Nebraska
FIGURE 3 – Bacterial ooze emerging from pod lesions

FACTORS FAVORING DEVELOPMENT 
• Warm temperatures 
• High humidity or leaf moisture 

IMPORTANT FACTS 
• Pathogens are seedborne 
• Spread can occur with any type of mechanical contact on wet leaves or by splashing water 
• Planting clean seed and use of disease resistant cultivars are the most effective management tools 
• Can be confused with fungal leaf spots

Powdery mildew

AUTHORS: Renuka N. Attanayake, Weidong Chen and Michael Wunsch 

SYMPTOMS 
• White powdery tufts of fungal growth 
• New fungal growth can be rubbed off easily 
• Fungal growth will expand and may cause plant tissue to become chlorotic 
• Late in the season, small black spherical fungal structures may appear 
• Infection on pods can cause a gray-brown discoloration of the seeds 

Figure 1
Photo Credit:
M. Wunsch, NDSU
FIGURE 1 – Small tufts of fungal growth
Figure 2
Photo Credit:
S. Markell, NDSU
FIGURE 2 – Progression of fungal growth
Figure 3
Photo Credit:
S. Markell, NDSU
FIGURE 3 – Fungal growth rubbed off right side of leaf
Figure 4
Photo Credit:
R. Attanayake, Washington St. U.
FIGURE 4 – Sever infection late in the season; note black fungal structures

FACTORS FAVORING DEVELOPMENT 
• Temperatures of 59 to 77 F are optimal 
• Heavy dew or fog 
• Late planting 

IMPORTANT FACTS 
• Pathogen can be soil-borne, seed-borne and wind-dispersed 
• Management tools include resistant cultivars, crop rotation and foliar fungicides 
• Most prevalent late in the season

Rust

AUTHORS: Sam Markell and Julie Pasche 

SYMPTOMS 
• Affects all above-ground plant parts 
• Pustules erupt from tissue, causing holes and large lacerations 
• Pustules are filled with dusty cinnamon-brown spore that easily rub off 
• Severe infection causes yellowing, premature senescence and yield loss 

Figure 1
Photo Credit:
S. Markell, NDSU
FIGURE 1 – Pustules filled with dusty brown spores on leaf


 

Figure 2
Photo Credit:
S. Markell, NDSU
FIGURE 2 – Pustules lacerating branch
Figure 3
Photo Credit:
S. Markell, NDSU
FIGURE 3 – Severe infection causing premature senescence and plant death

FACTORS FAVORING DEVELOPMENT 
• Heavy dew or fog 

IMPORTANT FACTS 
• Disease observed annually in northern Great Plains but rarely widespread 
• Epidemics can progress quickly once disease is established 
• Foliar fungicides can help manage disease 
• Also can infect lentils and garden peas

Septoria leaf spot

AUTHORS: Mary Burrows and Sam Markell 

SYMPTOMS 
• Symptoms occur on all plant parts 
• Necrotic lesions with small black fungal structures (pycnidia) 
• Often occur late in the season 

Figure 1
Photo Credit:
S. Markell, NDSU
FIGURE 1 – Young leaf lesion with black fungal structures (pycnidia)
Figure 2
Photo Credit:
S. Markell, NDSU
FIGURE 2 – Oblong lesions with pycnidia
Figure 3
Photo Credit:
S. Markell, NDSU
FIGURE 3 – Necrotic lesion with pycnidia on branch

FACTORS FAVORING DEVELOPMENT 
• Warm temperatures (70 to 80 F) 
• High humidity or heavy dews IMPORTANT FACTS 
• The pathogen survives on crop stubble or infected seed; spores are wind-dispersed 
• Planting clean seed, rotation and foliar fungicides are the most effective management tools 
• No variety resistance is known 
• Can be confused with Ascochyta blight and bacterial blight. Note that Septoria pycnidia are distributed randomly and Ascochyta pycnidia are distributed in a circular, target pattern. Bacterial blight does not have pycnidia.

Sclerotinia white mold

AUTHORS: Weidong Chen, Lyndon Porter and Kevin McPhee 

SYMPTOMS 
• Lesions occur on stems, leaves and pods 
• Lesions initially are water-soaked but appear bleached and necrotic as they age 
• White, puffy fungal growth (white mold) may appear on lesions 
• Mouse-dropping-sized black sclerotia may form on and in infected tissue 

Figure 1
Photo Credit:
K. McPhee, NDSU
FIGURE 1 – Water-soaked lesion on an infected plant
Figure 2
Photo Credit:
L. Porter, USDA-ARS Prosser, WA
FIGURE 2 – Necrotic lesions and white fungal tissue on stems and pods
Figure 3
Photo Credit:
W. Chen, USDA Pullman, WA
FIGURE 3 – A black sclerotium in a pea stem
Figure 4
Photo Credit:
K. McPhee, NDSU
FIGURE 4 – Apothecia (mushrooms) developed from sclerotia

FACTORS FAVORING DEVELOPMENT 
• Cool and moist conditions 
• Lush vegetative growth 
• Heavy canopy 

IMPORTANT FACTS 
• Sclerotia can survive for many years in soil 
• Pathogen infects most broadleaf crops 
• Plant-to-plant spread can occur by physical contact 
• Management tools include clean seed, fungicide applications, rotation to cereal crops and irrigation management

Botrytis gray mold

AUTHORS: Zhendong Zhu and Weidong Chen 

SYMPTOMS 
• Symptoms occur on all above-ground plant parts 
• Leaf lesions are water-soaked, grayish, irregular or circular lesions, with a concentric ring pattern 
• Stem lesions are initially fuzzy, gray lesions, later turn tan and girdle stem 
• Pod lesions are initially irregular or circular, water-soaked, later turn tan and sunken 
• Gray, fluffy mycelium are produced on lesions under conditions of high humidity 

Figure 1
Photo Credit:
Z. Zhu, Institute of Crop Sciences, CAAS
FIGURE 1 – Circular lesion with a concentric ring pattern on leaf
Figure 2
Photo Credit:
Z. Zhu, Institute of Crop Sciences, CAAS
FIGURE 2 – Tan lesions covered with grayish mycelium on tendrils
Figure 3
Photo Credit:
Z. Zhu, Institute of Crop Sciences, CAAS
FIGURE 3 – Tan lesions girdling stem
Figure 4
Photo Credit:
Z. Zhu, Institute of Crop Sciences, CAAS
FIGURE 4 – Tan, sunken lesions covered with grayish mycelium on pods

FACTORS FAVORING DEVELOPMENT 
• Cool and high humidity conditions 

IMPORTANT FACTS 
• Pathogen can survive in soil and plant debris or on growing plants 
• Pathogen can be dispersed by splashing water, wind, or farm machinery 
• Pathogen infests many plant species 
• Resistant cultivars are not available 
• Foliar fungicides can help manage disease

Downy Mildew

AUTHORS: Zhendong Zhu and Weidong Chen 

SYMPTOMS 
• Symptoms may be systemic or local 
• Systemically infected plants are stunted, distorted 
• Irregular-shaped lesions on leaf undersurface that contain fluffy brown, pink or grey fungal tissue, while on the top side, plant tissue is turned greenish-yellow to brown 
• Infected pods may be deformed and have yellow to brownish areas and superficial blistering 

Figure 1
Photo Credit:
Z. Zhu, Institute of Crop Sciences, CAAS
FIGURE 1 – Irregular-shaped lesions forming on undersurface of leaves turns plant tissue on top surface greenish-yellow to brown
Figure 2
Photo Credit:
Z. Zhu, Institute of Crop Sciences, CAAS
FIGURE 2 – Fluffy, mouse-grey fungal tissue on lower leaf surfaces
Figure 3
Photo Credit:
Z. Zhu, Institute of Crop Sciences, CAAS
FIGURE 3 – Yellow to brownish areas and superficial blistering on infected pod
Figure 4
Photo Credit:
Z. Zhu, Institute of Crop Sciences, CAAS
FIGURE 4 – Infection causing pod-cracking

FACTORS FAVORING DEVELOPMENT 
• Cool and moist conditions 
• Late planting 

IMPORTANT FACTS 
• Oospores can survive for 10-15 years in soil 
• Pathogen can be soil-borne, seed-borne and wind-dispersed 
• Management tools include resistant cultivars, crop rotation and foliar fungicides

Viruses

Alfalfa mosaic virus

AUTHORS: Lyndon Porter 

SYMPTOMS 
• Yellow mottling of foliar tissue (not always prominent) 
• Purple or brown streaks in leaf veins 
• Dead tissue on leaf or stem 

Figure 1
Photo Credit:
L. Porter, USDA-ARS Prosser, WA
FIGURE 1 – Yellow mottling of foliar tissue

FACTORS FAVORING DEVELOPMENT 
• Presence of pea and green peach aphids, which transmit the virus 
• Proximity to alfalfa fields 

IMPORTANT FACTS 
• Pea, green peach, foxglove, bean and potato aphids transmit the virus 
• No resistant cultivars are available 
• Insecticides may reduce secondary spread of virus by killing vectors (aphids) 
• Can be confused with pea streak virus

Bean leafroll or pea leafroll

AUTHORS: Lyndon Porter 

SYMPTOMS 
• Plants are yellow and stunted 
• New tissue is distorted and twisted while old growth may be normal 
• Leaflets curl downward and are brittle 

Figure 1
Photo Credit:
L. Porter, USDA-ARS Prosser, WA
FIGURE 1 – Yellow, distorted and twisted leaves
Figure 2
Photo Credit:
L. Porter, USDA-ARS Prosser, WA
FIGURE 2 – Down-curled leaves
Figure 3
Photo Credit:
L. Porter, USDA-ARS Prosser, WA
FIGURE 3 – Yellow and distorted new growth; old growth is normal

FACTORS FAVORING DEVELOPMENT 
• Presence of pea aphids transmitting the virus 

IMPORTANT FACTS 
• Virus is not seed-transmitted 
• Often occurs with pea enation mosaic virus 
• Later infections are less likely to have an impact on yield 
• Cultivars with resistance may be available 
• Can be confused with other viruses, root rots, herbicide damage or abiotic stress

Pea enation mosaic

AUTHORS: Lyndon Porter 

SYMPTOMS 
• Leaves may be brittle and have a mosaic of green and yellow rough bumps (enations), translucent spots or clear veins 
• Pods may be distorted and fill poorly 

Figure 1
Photo Credit:
L. Porter, USDA-ARS Prosser, WA
FIGURE 1 – Leaf with mosaic pattern and white/ clear spots (windows)
Figure 2
Photo Credit:
L. Porter, USDA-ARS Prosser, WA
FIGURE 2 – Misshapen pods
Figure 3
Photo Credit:
L. Porter, USDA-ARS Prosser, WA
FIGURE 3 – Enations (bumps) on leaf

FACTORS FAVORING DEVELOPMENT 
• Presence of pea aphids transmitting the virus 

IMPORTANT FACTS 
• Virus is not seed-transmitted 
• Often occurs with bean leaf roll virus 
• Early infections more severely impact yield than late infections 
• Insecticides may reduce secondary spread of virus by killing vectors (aphids) 
• Can be confused with other viruses, herbicide damage Card 1

Pea streak

AUTHORS: Lyndon Porter 

SYMPTOMS 
• Purple to brown streaks on leaves, stems and pods 
• Leaf-yellowing and dieback of growing tips 
• Pods may appear blistered, deformed and fill poorly 
• Streaks on pods differ in size and shape and often are sunken 

Figure 1
Photo Credit:
L. Porter, USDA-ARS Prosser, WA
FIGURE 1 – Malformed pea pods with blistering
Figure 2
Photo Credit:
L. Porter, USDA-ARS Prosser, WA
FIGURE 2 – Purple sunken streaks on infected plants

FACTORS FAVORING DEVELOPMENT 
• Presence of pea or green peach aphid transmitting virus 

IMPORTANT FACTS 
• Virus is not seed-transmitted 
• Virus also can infect alfalfa, red and white clover, and vetch 
• Rarely associated with significant damage in pea fields 
• Insecticides may reduce secondary spread of virus by killing vectors (aphids) 
• Can be confused with other viruses, herbicide or abiotic damage