Soybean leaf diseases pictures

Soybean leaf diseases pictures DEFAULT

Soybean

Pests

Category : Insects

Armyworms (Beet armyworm, Western striped armyworm) Spodoptera exigua
Spodoptera praefica

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Beet armyworm larvae feeding on soybean leaves

Symptoms

Singular, or closely grouped circular to irregularly shaped holes in foliage; heavy feeding by young larvae leads to skeletonized leaves; shallow, dry wounds on fruit; egg clusters of eggs may be present on the leaves; egg clusters are covered in a whitish scale which gives the cluster a cottony or fuzzy appearance; young larvae are pale green to yellow in color while older larvae are generally darker green with a dark and light line running along the side of their body and a pink or yellow underside

Cause

Insect

Comments

Management
Organic methods of controlling armyworms include biological control by natural enemies which parasitize the larvae and the application of Bacillus thuringiensis; there are chemicals available for commercial control but many that are available for the home garden do not provide adequate control of the larvae

Cucumber beetles (Western striped cucumber beetle, Western spotted cucumber beetle) Acalymma vittata
Diabrotica undecimpunctata

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Spotted cucumber beetle on soybean

Symptoms

Stunted seedling; damaged leaves, stems and/or petioles; reduced plant stand; plants may exhibit symptoms of bacterial wilt; scars on fruit caused by beetle feeding damage; adult beetles are brightly colored with either a green-yellow background and black spots or alternating black and yellow stripe

Cause

Insect

Comments

Management
Monitor new planting regularly for signs of beetle; floating row covers can be used to protect the plants from damage but will need to be removed at bloom to allow bees to pollinate plants; applications of kaolin clay can be effective for management of small beetle populations; application of appropriate insecticides may be necessary

Mexican bean beetle Epilachna varivestis

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Mexican bean beetle and damage to soybean foliage

Symptoms

Irregular patches of feeding damage on underside of leaves which causes the top surface of the leaf to dry out, giving the leaves a lacy appearance; insect will also damage flowers and small pods; pods may be damaged so badly that they drop from the plant; adult insect is an orange-brown beetle with black spots; larvae are fat-bodied grubs which taper at the end and are in rows of conspicuous spines

Cause

Insect

Comments

Management
Some bean varieties may be less attractive hosts for the beetle, e.g. snapbeans are preferred hosts over lima beans; early varieties may escape damage form beetles beetle populations can be reduced by remove overwintering sites such as brush and leaves on the ground; handpick larvae and adults; brush eggs from leaves and destroy; apply insecticidal soap to leaf undersides if infestation is heavy

Category : Others

Brown spot Septoria glycines

Symptoms

Upper leaves have light purple discoloration and a leathery appearance and bronzing of leaves may occur; red-purple angular or irregularly shaped lesions develop on both the upper and lower leaf surfaces and may coalesce to form large necrotic patches; multiple infections can cause chlorosis and defoliation of the plants; on petioles and stems, sunken red-purple lesions may develop and upper leaves appear blighted.

Cause

Fungus

Comments

Management
Plow crop residue into soil after harvest; plant soybean varieties that are less suceptible to the disease; rotate crops to a non-susceptible crop for at least one year; apply an appropriate foliar fungicide to protect plants from bloom to pod fill

Cercospora leaf blight Cercospora kikuchii

Symptoms

Upper leaves turning yellow; purple-red lesions are present on leaves and coalesce to give the leaves a bronzed appearance; leaves develop a leathery texture; severe infections give leaves a blighted appearance and cause them to drop from the plant

Cause

Fungus

Comments

Management
No soybean varieties are immune to the disease but some have more resistance than others and can give some degree of control; crop debris should be plowed into soil following harvest to reduce build up of inoculum

Charcoal rot Macrophomina phaseolina

Symptoms

Discoloration of stem at soil line; cankers on stem may spread upwards; leaves may wilt and drop from plant; numerous small black sclerota (fungal fruiting bodies) develop in affected tissues and can be used to diagnose the disease

Cause

Fungus

Comments

Management
Organic soil amendments such as the addition of manure or neemcake can be used to reduce levels of inoculum in the soil

Downy mildew Peronospora manshurica

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Downy mildew symptoms on soybean leaf

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Downy mildew symptoms on soybean leaf

Symptoms

Yellow or pale green spots on upper surfaces of leaves which enlarge and coalesce to form yellow patches; lesions may turn gray-brown to dark brown with a yellow margin; fuzzy tufts of gray-purple mold develop on lesions on underside of leaves; infection of pods can cause seeds to be covered in masses of white mycelia with pods showing no external symptoms

Cause

Fungus

Comments

Management
Treat seeds with an appropriate fungicide prior to planting; plow soybean residue into soil after harvest; grow soybean varieties which are resistant to the disease where possible; rotate crop away from soybean for a one year period

Frogeye leaf spot Cercospora sojina

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Frogeye leafspot lesions on soybean foliage

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Frogeye leafspot lesions on soybean foliage

Symptoms

Angular gray spots with purple to red-brown edges on leaves; brown to black fungal structures developing in the center of the spot; circular or elongated lesions where inner membrane of pod contacts the seeds;

Cause

Fungus

Comments

Management
Plant high quality seed and use resistant varieties; rotate crop away from soybean for a period of 2 years; treat seeds with appropriate fungicide prior to planting; apply appropriate foliar fungicide

Phytophthora rot Phytophthora megasperma

Symptoms

Susceptible varieties of soybean may have water-soaked stems and yellowing leaves; yellowing occurs between leaf veins and along leaf margins; upper leaves of plant become chlorotic and wilted; tolerant soybean varieties may show stunted growth and slight yellowing

Cause

Oomycete

Comments

Management
Plant soybean varieties that are resistant to the disease - ensure variety is resistant to all races of fungus present in the field; treat seeds with an appropriate fungicide prior to planting; plant soybean in soild with good drainage

Sours: https://plantvillage.psu.edu/topics/soybean/infos

Photo by Markell, NDSU

Cover photo: Sam Markell, NDSU

Root Diseases

Fusarium root rot

Fusarium solani, F. oxysporum, F. tricinctum and other Fusarium species (fungi)

Fusarium root rot, Photo by B Nelson, NDSU

FIGURE 1 – Dark brown/black discoloration of roots
Photo: B. Nelson, NDSU

Photo by Giesler, U of NE

FIGURE 2 – Root rot and dieback of tap root
Photo: Giesler, Univ. of Nebraska

Photo by J Bienapfl, U of M

FIGURE 3 – Seedling damping-off
Photo: J. Bienapfl, Univ. of Minnesota


Photo by D Mueller, IA State U

FIGURE 4 – Plant chlorosis
Photo: D. Mueller, Iowa State Univ.

AUTHORS: Dean Malvick and Sam Markell

SYMPTOMS

• Brown to black discoloration and rot of roots, especially the taproot
• Plant stunting and yellowing of leaves may occur if root rot is severe
• Seedling damping-off

FACTORS FAVORING DEVELOPMENT

• Soil compaction
• Presence of soybean cyst nematode (SCN)
• Plant stress
• Drought

IMPORTANT FACTS

• Disease can infect and kill seedlings and damage older plants
• Fusarium survives for long periods in soil
• Dry edible beans, corn and pulse crops are hosts
• Fusarium is dispersed with soil (on equipment, in water, by wind, etc.)
• Management: improve soil drainage, reduce compaction, fungicide seed treatments
• Commonly confused with other roots rots, SCN and iron deficiency chlorosis

Phytophthora root and stem rot

Phytophthora sojae (oomycete)

Photo by A Dorrance, OH State Univ

FIGURE 1 – Close-up of lower stem lesion
Photo: D. Malvick, Univ. of Minnesota

Photo by D Malvick, U of M

FIGURE 2 – Lower stem lesion and wilting
Photo: D. Malvick, Univ. of Minnesota

Photo by A Dorrance, OH State U

FIGURE 3 – Severe infection in field
Photo: A. Dorrance, Ohio State Univ.

AUTHORS: Sam Markell, Dean Malvick and Berlin Nelson

SYMPTOMS

• Seeds may rot and/or seedlings may die before or after emergence (damping-off)
• Mid- to late-season symptoms include a chocolate brown stem lesion extending up from the soil line
• Leaf chlorosis, necrosis and plant wilting can develop
• Frequently occurs in patches of fields and low areas

FACTORS FAVORING DEVELOPMENT

• Excessive moisture, saturated soil and/or flooding, especially early in the season
• Poorly drained, heavy clay or compacted soils
• Short/no crop rotation

IMPORTANT FACTS

• Can cause significant yield loss
• The pathogen is specific to soybeans
• Management tools available include genetic resistance and seed treatments
• The pathogen has many pathotypes and many can overcome Rps genetic resistance
• Commonly confused with other root rot diseases

Pythium root rot

Pythium ultimum and other Pythium species (oomycete)

Photo by D Malvick, U of M

FIGURE 1 – Seed rotting due to Pythium
Photo: D. Malvick, Univ. of Minnesota

Photo by M Chilver, Michigan State Univ

FIGURE 2 – Damping-off of seedlings
Photo: M. Chilvers, Michigan State Univ.

Photo by A Robertson, IA State Univ

FIGURE 3 – Light brown infected roots
Photo: A. Robertson, Iowa State Univ.

AUTHORS: Dean Malvick and Sam Markell

SYMPTOMS

• Soft, slimy rot of seeds in ground
• Light brown rot of outer part of roots (cortex)
• Damping-off of seedlings

FACTORS FAVORING DEVELOPMENT

• Persistent wet soil after planting
• Soil compaction, heavy soil with high clay content
• Slow growth of seedlings and plant stress

IMPORTANT FACTS

Pythium survives for years in soil
• Pathogen causes most damage to seeds and seedlings, but may damage roots of older plants
• Dry edible beans, corn and other crops can be hosts
Pythium is dispersed with soil (on equipment, in water, by wind, etc.)
• Management: improve soil drainage, reduce compaction, some seed treatments
• Symptoms on seed and seedlings very similar to Phytophthora damage
• Commonly confused with other seedling diseases

Rhizoctonia root rot

Rhizoctonia solani (fungus)

Photo by D Malvick, U of MN

FIGURE 1 – Rusty-brown lesions on soybean stems
Photo: D. Malvick, Univ. of Minnesota

Photo by D Malvick, U of MN

FIGURE 2 – Soybean seedlings with girdled stems
Photo: D. Malvick, Univ. of Minnesota

Photo by D Malvick, U of MN

FIGURE 3 – Seedlings dying in a row
Photo: D. Malvick, Univ. of Minnesota

AUTHORS: Dean Malvick and Sam Markell

SYMPTOMS

• Rusty-brown, dry, sunken lesions on lower parts of stems
• Dark brown lesions than girdle the stems near the soil
• Plants stunted, yellow, and wilting

FACTORS FAVORING DEVELOPMENT

• Warm and moist soil while plants are in early vegetative stages
• Delayed planting in spring due to rain
• High soil organic matter
• Plant stress due to physical or chemical/herbicide injury

IMPORTANT FACTS

• Dry edible beans, corn, sugar beet and pulse crops can be hosts
• Causes most damage to plants in early vegetative growth stages
Rhizoctonia is dispersed with soil (on equipment, in water, by wind, etc.)
• Management: some seed treatments, crop rotation, tillage, early planting
• Soybean varieties vary in susceptibility to Rhizoctonia
• Commonly confused with other roots rots

Seed and seedling disease complex

Pythium (oomycete), Phytophthora (oomycete), Rhizoctonia (fungus), Fusarium (fungus)

Photo by D Malvick, U of MN

FIGURE 1 – Seedling decomposing due to infection
Photo: D. Malvick, Univ. of Minnesota

Photo by D Malvick, U of MN

FIGURE 2 – Pre-emergence death of seedling
Photo: D. Malvick, Univ. of Minnesota

Photo by D Malvick, U of MN

FIGURE 3 – Post-emergence death of seedling
Photo: D. Malvick, Univ. of Minnesota

AUTHORS: Dean Malvick and Sam Markell

SYMPTOMS

• Rotting of seed in the ground
• Pre-emergence death
• Post-emergence death and stunting
• Soft, tan roots with intact steel (Pythium and Phytophthora)
• Dark brown discoloration and rot of tap roots (Fusarium)
• Rusty-brown lesions on stem and roots (Rhizoctonia)

FACTORS FAVORING DEVELOPMENT

• Wet soil
• Delayed germination and growth
• Poor-quality seed
• Plant stress

IMPORTANT FACTS

• Pathogens are favored by different conditions for infection and disease development
• Multiple pathogens often infect seeds/seedlings
• Difficult to diagnose principle pathogen
• Symptoms can look similar for different pathogens, but management may differ
• Management options: soil drainage, tillage, varieties with resistance, seed treatments
• Seed treatment ingredients vary in efficacy for different pathogens
• Commonly confused with water damage

Soybean cyst nematode (SCN)

Heterodera glycines (plant parasitic nematode)

Photo by S Markell, NDSU

FIGURE 1 – White SCN females (cysts) and a nodule on soybean roots
Photo: S. Markell, NDSU

Photo by S Markell, NDSU

FIGURE 2 – Mature brown cysts
Photo: S. Markell, NDSU

Photo by S Markell, NDSU

FIGURE 3 – Yellowed areas near field entrance caused by severe SCN
Photo: S. Markell, NDSU

AUTHORS: Sam Markell and Dean Malvick

SYMPTOMS

• Small (approximately 1/32 inch) lemon-shaped female worms (cysts) on roots
• Cysts’ color ranges from cream to dark brown
• Above-ground symptoms often are absent
• Soybeans can become stunted and yellow

FACTORS FAVORING DEVELOPMENT

• Short crop rotation with soybeans and/or dry edible beans
• High soil pH, light soil texture
• Dry growing seasons

IMPORTANT FACTS

• SCN is the most yield-limiting disease in the U.S.
• SCN can make other diseases (sudden death syndrome, brown stem rot) worse
• Soybeans, dry edible beans and several weeds are hosts
• SCN is dispersed with soil (on equipment, in water, by wind, etc.)
• Soil testing is the most reliable way to determine if you have SCN
• Management tools available include crop rotation, variety resistance and possibly seed treatments
• SCN is overcoming PI genetic resistance
• Commonly confused with roots rots, iron deficiency chlorosis, other abiotic stress

Sudden death syndrome (SDS)

Fusarium virguliforme (fungus)

Photo by D Malvick, U of M

FIGURE 1 –  Internal stem browning
Photo: D. Malvick, Univ. of Minnesota

Photo by D Malvick, U of M

FIGURE 1 – Early chlorotic blotches between veins
Photo: D. Malvick, Univ. of Minnesota

Photo by D Malvick, U of M

FIGURE 2 – Severe leaf symptoms
Photo: D. Malvick, Univ. of Minnesota

Photo by D Malvick, U of MN

FIGURE 3 – Severe infection in a patch in a field
Photo: D. Malvick, Univ. of Minnesota

Photo by D Malvick, U of MN

FIGURE 4 – Root rot and blue fungal growth on root
Photo: D. Malvick, Univ. of Minnesota

AUTHORS: Dean Malvick and Sam Markell

SYMPTOMS

• Yellow and brown discoloration between leaf veins
• Tan stem under the epidermis near the soil line, while pith remains white
• Symptoms develop in plant seed fill stages (August)
• Leaflets can fall and petioles remain attached to plant
• Root rot and occasionally blue fungal growth on root

FACTORS FAVORING DEVELOPMENT

• Wet soil for two to four weeks after planting
• Field history of SDS
• Compacted soil, poor drainage
• Periodic heavy rain and moist soil through mid-Aug.
• High soybean cyst nematode populations

IMPORTANT FACTS

• Common in southern and central Minnesota, less common (but increasing) in northern Minnesota and North Dakota
• Pathogen can cause root rot of dry edible bean and some other legumes
• Pathogen dispersed with soil (on equipment, in water, by wind, etc.)
• Management options include varieties with resistance to SDS and seed treatments
• Commonly confused with brown stem rot

Stem Diseases

Anthracnose

Colletotrichum truncatum or other Colletotrichum species (fungi)

Photo by D Malvick, U of MN

FIGURE 1 – Irregular-shaped blotches on stem
Photo: D. Malvick, Univ. of Minnesota

Photo by S Markell, NDSU

FIGURE 2 – Abundant black fungal growths of irregular arrangement and size
Photo: S. Markell, NDSU

Photo by S Markell, NDSU

FIGURE 3 – Close-up appearance of fungal growths
Photo: S. Markell, NDSU

AUTHORS: Sam Markell and Dean Malvick

SYMPTOMS

• Symptoms usually not seen until plants reach maturity
• Dark brown patches may appear on stems, pods and petioles
• Small black fungal spots develop in irregular patterns on stems, pods and petiole
• Black, infected areas covered with tiny black spines (setae) that can be seen with a 10X hand lens

FACTORS FAVORING DEVELOPMENT

• Warm and wet/humid weather
• Planting infected seed
• Short/no crop rotation

IMPORTANT FACTS

• A common late-season disease that rarely causes significant yield loss
• Pathogen(s) have a wide host range and may infect other legume crops and weeds
• Pathogen can be seedborne
• Commonly confused with pod and stem blight, stem canker, charcoal rot

Brown stem rot (BSR)

Cadophora gregata (fungus)

Photo by D Malvick, U of MN

FIGURE 1 – Light brown discoloration in pith and leaf
Photo: D. Malvick, Univ. of Minnesota

Photo by D Malvick, U of MN

FIGURE 2 – Dark brown discoloration in pith of stem
Photo: D. Malvick, Univ. of Minnesota

Photo by D Malvick, U of MN

FIGURE 3 – Brown and yellow discoloration between veins
Photo: D. Malvick, Univ. of Minnesota

Photo by D Malvick, U of MN

FIGURE 4 – Symptoms on leaves of whole plant
Photo: D. Malvick, Univ. of Minnesota

AUTHORS: Dean Malvick and Sam Markell

SYMPTOMS

• Brown pith in stem, especially in lower stem
• Brown and yellow discoloration between leaf veins may be present
• Symptoms commonly develop in mid-August

FACTORS FAVORING DEVELOPMENT

• Short/no crop rotation
• Wet and cool weather in July/August
• History of disease in a field
• Susceptible soybean varieties
• Presence of soybean cyst nematode

IMPORTANT FACTS

• Stems should be longitudinally split to identify BSR
• Commonly confused with sudden death syndrome
• Pathogen overwinters/survives in infected soybean stems
• BSR pathogen dispersed with soil (on equipment, in water, by wind, etc.)
• Soybean is only known definite host
• Two pathogen types: type A causes leaf and stem symptoms; type B primarily internal stem symptoms only
• Type B more common in our region
• Management options: crop rotation and varieties resistant to BSR

Charcoal rot

Macrophomina phaseolina (fungus)

Photo B. Nelson, NDSU

FIGURE 1 – Large patch of soybean with charcoal rot
Photo: B. Nelson, NDSU

Photo, B. Nelson, NDSU

FIGURE 2 – Patch of wilting soybeans
Photo: B. Nelson, NDSU

Photo, B. Nelson, NDSU

FIGURE 3 – Infected (L and C) and healthy soybean (R)
Photo: B. Nelson, NDSU

Photo, S. Markell, NDSU

FIGURE 4 – External gray lesion peeling away, revealing profuse "charcoal" sclerotia
Photo: S. Markell, NDSU

AUTHORS: Sam Markell and Dean Malvick

SYMPTOMS

• Symptoms usually not apparent until flowering or later
• Taproot and lower stem may appear gray/silver
• Numerous black fungal specks (microsclerotia) under epidermis give a “charcoal” appearance
• Premature death with wilted leaves attached
• Frequently occurs in patches in fields

FACTORS FAVORING DEVELOPMENT

• Hot temperatures
• Drought stress

IMPORTANT FACTS

• Yield loss may occur in hot, dry growing seasons
• Disease typically most severe in drought-prone areas of fields
• Very wide host range, which includes corn, sunflower, other legume crops and weeds
• Commonly confused with anthracnose, Phytophthora stem rot, pod and stem blight, stem canker

Pod and stem blight/Phomopsis seed decay

Diaporthe longicolla (fungi) and D. sojae

Photo by D Marvick, U of MN

FIGURE 1 – Linear rows of raised black dots
Photo: D. Malvick, Univ. of Minnesota

Photo by D Marlvick, U of MN

FIGURE 2 – Infected (L) and healthy (R) plants
Photo: D. Malvick, Univ. of Minnesota

AUTHORS: Sam Markell and Dean Malvick

SYMPTOMS

• Small, raised black dots (pycnidia) arranged in distinct rows on stem, pods and petioles
• Tops of plants may discolor and die, leading to plant death
• Symptoms often not apparent until plants near maturity
• Wavy, black zone lines inside infected stems and roots may occur (see stem canker)
• Seed may be cracked, shriveled, moldy and have poor germination

FACTORS FAVORING DEVELOPMENT

• Warm and humid weather
• Short/no crop rotation
• Planting infected seed
• Delayed harvest due to wet weather

IMPORTANT FACTS

• Yield loss and reduction in seed quality may occur
• Host range includes dry edible bean and dry edible pea
• Pathogen survives in crop residue and seed
• Pathogen is widespread, even in apparently healthy plants
• Black dots arranged in rows are diagnostic (anthracnose and charcoal rot dots are random)
• Commonly confused with anthracnose, charcoal rot and stem canker

Stem canker

Diaporthe caulivora (northern stem canker) and D. aspalathi (southern stem canker) (fungi)

Photo by D Malvick, U of MN

FIGURE 1 – Reddish-brown stem canker lesion
D. Malvick, Univ. of Minnesota

Photo by S Markell, NDSU

FIGURE 2 – Sunken canker on lower stem of mature plant
Photo: S. Markell, NDSU

Photo by S Markell, NDSU

FIGURE 3 – Zone lines beneath epidermis of sunken canker
Photo: S. Markell, NDSU

AUTHORS: Sam Markell and Dean Malvick

SYMPTOMS

• Reddish-brown lesions on the lower stem starting at branch points/nodes
• Lesions expand and may become sunken cankers
• Tiny black fungal structures may be produced on lesions
• Narrow black “zone lines” sometimes under epidermis, but importantly, zone lines also are associated with pod and stem blight

FACTORS FAVORING DEVELOPMENT

• Extended periods of wet weather (one to four days) with moderate temperatures (70 to 85 F)
• Short/no crop rotation in fields with history of disease
• Reduced tillage

IMPORTANT FACTS

• Yield loss can occur if disease is widespread in a field and kills plants before pod fill
• Management tools include crop rotation (wheat, corn, etc.), resistant varieties and foliar fungicides
• Commonly confused with anthracnose, charcoal rot, late-season Phytophthora root rot, and pod and stem blight

White mold (Sclerotinia stem rot)

Sclerotinia sclerotiorum (fungus)

Photo by D Malvick, U of MN

FIGURE 1 – Lesions with white mold and sclerotia
Photo: D. Malvick, Univ. of Minnesota

Photo by M Gilley, NDSU

FIGURE 2 – Severe white mold infection
Photo: M. Gilley, NDSU

Photo by S Markell, NDSU

FIGURE 3 – Black sclerotia among shriveled seeds
Photo: S. Markell, NDSU

Photo by S Markell, NDSU

FIGURE 4 – Apothecia
Photo: S. Markell, NDSU

AUTHORS:Sam Markell and Dean Malvick

SYMPTOMS

• Stem lesions begin as water-soaked spots near nodes
• Lesions enlarge, fluffy white fungal growth develops on moist stems
• Infected stems become bleached white and may shred
• Hard black structures (sclerotia) form on and in infected tissue

FACTORS FAVORING DEVELOPMENT

• Wet soils prior to and during soybean flowering
• Frequent wetness (rain, fog, heavy dew) and cool temperatures during bloom
• Dense plant canopy, high fertility, high plant populations
• History of white mold in field

IMPORTANT FACTS

• Severe yield losses can occur when July and early August are cool and wet
• Many broadleaf crops and weeds are hosts
• Pathogen survives in soil for many years as sclerotia
• Sclerotia produce apothecia (about 1/4-inch mushrooms), which produce ascospores that initiate infection
• Management options: partially resistant varieties, increase plant spacing and fungicides
• Apothecia commonly confused with bird’s nest fungi

Leaf Diseases

Bacterial blight

Pseudomonas savastanoi pv. glycinea (bacteria)

Photo by S Markell, NDSU

FIGURE 1 – Brown angular lesions with bright yellow halos
Photo: S. Markell, NDSU

Photo by S Markell, NDSU

FIGURE 2 – Coalescing lesions and leaf tattering
Photo: S. Markell, NDSU

Photo by S Markell, NDSU

FIGURE 3 – Magnified lesions
Photo: S. Markell, NDSU

AUTHORS: Sam Markell and Dean Malvick

SYMPTOMS

• Typically observed first in upper canopy in July
• Small, water-soaked and angular leaf lesions
• Lesion centers turn brown and are surrounded by a bright yellow halo
• Lesions often coalesce and leaves will tatter
• Often widespread distribution in field

FACTORS FAVORING DEVELOPMENT

• Cool temperatures, frequent rains and thunderstorms
• Weather that damages plant tissue (hail, high winds, etc.)
• Short/no crop rotation
• Planting infected seed

IMPORTANT FACTS

• Widespread but rarely economically important
• Lesions may occur on stem, petiole and pod
• Pathogen survives and can be spread with seed and infested crop residue
• Fungicides are not effective
• Commonly confused with Septoria brown spot, bacterial pustule, downy mildew

Bacterial pustule

Xanthomonas axonopodis pv. glycines (bacteria)

Photo by S Markell, NDSU

FIGURE 1 – Lesions with chlorotic halos on upper side of leaf
Photo: S. Markell, NDSU

Photo by S Markell, NDSU

FIGURE 2 – Lesions and pustules on underside of leaf
Photo: S. Markell, NDSU

Photo by S Markell, NDSU

FIGURE 3 – Pustules (approximately 5 to 10X)
Photo: S. Markell, NDSU

AUTHORS: Sam Markell and Dean Malvick

SYMPTOMS

• Lesions begin as small (1/16 to 1/4 inch) light green specks with yellow halos
• Lesion centers turn brown
• Raised pustules appear in lesions

FACTORS FAVORING DEVELOPMENT

• Wet and rainy weather
• Prolonged humid conditions
• Warm to hot temperatures

IMPORTANT FACTS

• Sporadic in Minnesota and North Dakota
• Unlikely to cause yield loss
• Can be mistaken for soybean rust, a disease that has not occurred in Minnesota or North Dakota
• Commonly confused with bacterial blight or Septoria brown spot

Bean pod mottle virus

Photo by A Dorrance, OH State Univ

FIGURE 1 – Light green to yellow leaf mottling
Photo: A. Dorrance, Ohio State Univ.

Photo by A Dorrance, OH State Univ

FIGURE 2 – Wrinkling, puckering and light green mottling
Photo: A. Dorrance, Ohio State Univ.

Photo by Univ of IL

FIGURE 3 – Leaf puckering and wrinkling
Photo: Univ. of Illinois

AUTHORS: Dean Malvick and Sam Markell

SYMPTOMS

• Green to yellow mottling of young leaves
• Leaves may become puckered and wrinkled
• Symptoms may not be visible during high temperatures or after pod set
• Seed may become mottled with dark stains

FACTORS FAVORING DEVELOPMENT

• High populations of bean leaf beetle (or other beetles) early in the season
• Cool weather

IMPORTANT FACTS

• Not thought to be common in Minnesota and North Dakota
• Virus can be transmitted by bean leaf beetle or other leaf feeding beetles
• Infection primarily occurs early in the season
• Host range includes dry edible bean, clovers and other legumes
• Management options: delay planting, seed applied insecticides
• Commonly confused with other viruses and possibly herbicide injury

Cercospora leaf blight

Cercospora kikuchii (fungus)

Photo by AK Chanda U of MN


FIGURE 1 – Purple discoloration of leaf
Photo: A.K. Chanda, Univ. of Minnesota

Photo by AK Chanda, U of MN

FIGURE 2 – Bronze discoloration and death of leaf tissue
Photo: A.K. Chanda, Univ. of Minnesota

Photo by Univ of IL

FIGURE 3 – Purple seed stain
Photo: Univ. of Illinois

AUTHORS: Dean Malvick and Sam Markell

SYMPTOMS

• Purple to bronze discoloration of upper leaf surfaces
• Red-brown spots on both leaf surfaces
• Large necrotic areas can develop on leaves, followed by leaf drop
• Seed coats can develop purple discoloration

FACTORS FAVORING DEVELOPMENT

• High humidity and warm temperatures
• Lack of crop rotation

IMPORTANT FACTS

• Disease is more common and severe in southern U.S.
• Pathogen overwinters on infested soybean debris and seed
• Plants susceptible from flowering to maturity
• Management options: pathogen-free seed, susceptible varieties, crop rotation and fungicides
• Commonly confused with sunscald

Downy mildew

Peronospora manshurica (Oomycete)

Photo by S Markell, NDSU

FIGURE 1 – Discrete lesions top side of leaf
Photo: S. Markell, NDSU

A. Underside of leaf, Photo by S Markell, NDSU

B. magnification of fungal growth on underside of leaf

FIGURE 2 – Fungal growth opposite lesions on underside of leaf (A) and the magnification of fungal growth (B)
Photo: S. Markell, NDSU

Photo by D Helland Wilbur Ellis

FIGURE 3 – Severe infection
Photo: D. Helland, Wilbur Ellis

AUTHORS:Sam Markell and Dean Malvick

SYMPTOMS

• Lesions begin as discrete pale green to light yellow spots on top side of leaves
• Fluffy tan tufts of fungal growth occur opposite lesions on underside of leaves
• Lesions become brighter yellow and turn brown with age

FACTORS FAVORING DEVELOPMENT

• Frequent and prolonged periods of high humidity or free moisture (dew)
• Moderate temperatures
• Short crop rotation
• Planting infected seed or field history of downy mildew

IMPORTANT FACTS

• Yield loss thought to be rare; however, severe outbreaks have occurred in North Dakota and Minnesota
• Pathogen is specific to soybeans and will not cause downy mildew of other crops
• Can be confused with Septoria brown spot, powdery mildew and bacterial diseases

Frogeye leaf spot

Cercospora sojina (fungus)

Photo by S. Markell, NDSU

FIGURE 1 – Lesions of various size and stages of development
Photo: S. Markell, NDSU

Photo by D Malvick, U of MN

FIGURE 2 – Spots and patterns of lesion development on leaf
Photo: D. Malvick, Univ. of Minnesota

Photo by S. Markell, NDSU

underside of Frogeye leaf spot with fuzzy gray mold

FIGURE 3 – Upper and underside of lesion with fuzzy gray mold.
Photo: S. Markell, NDSU

AUTHORS: Dean Malvick and Sam Markell

SYMPTOMS

• Brown leaf spots surrounded by a darker reddish-brown or purple ring
• Centers of spots become tan as they age and develop black specks
• Spots may coalesce, fall out and kill large parts of leaves

FACTORS FAVORING DEVELOPMENT

• Warm and humid weather
• Highly susceptible soybean varieties

IMPORTANT FACTS

• Disease more common in southern areas of the Midwest
• Pathogen overwinters in infected soybean residue and seed
• Management options: crop rotation, tillage and fungicides
• Pathogen resistance to strobilurin (QoI, FRAC 11) fungicides is common in Minnesota and North Dakota
• Commonly confused with bacterial blight, Phyllosticta leaf spot and Septoria brown spot

Phyllosticta leaf spot

Phyllosticta sojicola (fungi)

Phyllosticta leaf spot with gray irregular-shaped lesions with dark, narrow margins

FIGURE 1 - Gray irregular-shaped lesions with dark, narrow margins
Photo: K. Bissonnette

V-shaped Phyllosticta lesion with small black specs

FIGURE 2 - V-shaped lesion with small black specs (pycnidia)
Photo: K. Bissonnette

Large Phyllosticta lesion with numerous pycnidia

FIGURE 3 - Large lesion with numerous pycnidia
Photo: K. Bissonnette

AUTHORS: Sam Markell and Dean Malvick

SYMPTOMS

  • May occur anytime in growing season
  • Leaf lesions begin as pale green spots
  • Lesions become gray to tan with narrow dark purple to brown margin
  • Lesions may be oval, circular, irregular or V-shaped
  • Small black specs (pycnidia) may appear in lesion centers
  • Lesions also may occur on petioles, stems and pods

FACTORS FAVORING DEVELOPMENT

  • Cool temperatures
  • Wet conditions
  • Short crop rotations
  • Infected Seed

IMPORTANT FACTS

  • Minor soybean disease that rarely impacts yield
  • Appears to be uncommon in Minnesota and North Dakota
  • Pathogen survives in infested crop residue and seed
  • Commonly confused with frogeye leaf spot, bacterial blight, Septoria brown spot

Powdery mildew

Erysiphe diffusa and E. glycines (fungi)

Photo by D Malvick, U of MN

FIGURE 1 – White tufts of fungal growth
Photo: D. Malvick, Univ. of Minnesota

Photo by D Malvick, U of MN

FIGURE 2 – Severe infection covering leaf
Photo: D. Malvick, Univ. of Minnesota

Photo by D Malvick, Univ of MN

FIGURE 3 – Infection spreading in hot spot
Photo: D. Malvick, Univ. of Minnesota

AUTHORS: Sam Markell and Dean Malvick

SYMPTOMS

• Powdery white tufts of fungal growth on upper side of leaf
• Fungal growth may look like white flour sprinkled on the leaves
• Fungal growth can expand and may cover entire leaf surface
• Small black specs in growth may be observed late in season
• White fungal growth can be rubbed off leaf easily

FACTORS FAVORING DEVELOPMENT

• Temperatures from 64 to 75 F
• Low humidity with periods of limited leaf wetness
• Late-planted soybeans

IMPORTANT FACTS

• Yield loss is rare in Minnesota and North Dakota
• Usually occurs late in growing season
• The pathogen also may infect dry edible beans and field peas
• Commonly confused with downy mildew

Septoria brown spot

Septoria glycines (fungus)

Photo by D Malvick, U of MN

FIGURE 1 – Brown spots and chlorosis
Photo: D. Malvick, Univ. of Minnesota

Photo by D Malvick, U of MN

FIGURE 2 – Trifoliate with brown spots and chlorosis
Photo: D. Malvick, Univ. of Minnesota

Photo by D Malvick, U of MN

FIGURE 3 – Common pattern of symptoms developing in lower canopy
Photo: D. Malvick, Univ. of Minnesota

AUTHORS: Dean Malvick and Sam Markell

SYMPTOMS

• Dark brown spots (less than 1/8 inch diameter)
• Brown spots coalesce into large brown areas
• Irregular brown and yellow patches on one side of leaf
• Symptoms first develop in lower part of plant, then move up

FACTORS FAVORING DEVELOPMENT

• Wet and warm weather
• High plant density
• Continuous soybean planting
• Minimum tillage

IMPORTANT FACTS

• Typically does not cause yield loss
• Under severe conditions, defoliation and yield loss can occur
• Pathogen survives on infected residue and may be transmitted by seed
• Soybean varieties may vary in susceptibility
• Management options: crop rotation and fungicides
• Commonly confused with bacterial blight

Soybean mosaic virus

Photo by A Tenuta, OMADEA, Ontario Canada

FIGURE 1 – Leaf mottling and curling
Photo: A. Tenuta, OMAFRA, Ontario, Canada

Photo by A Tenuta, OMAFRA, Ontario Canada

FIGURE 2 – Discolored seed
Photo: A. Tenuta, OMAFRA, Ontario, Canada

AUTHORS: Sam Markell and Dean Malvick

SYMPTOMS

• Light and dark green mottling of leaves
• Leaf puckering and downward curling
• Symptoms most severe on youngest leaves
• Flattening of pods, reduced seed size, seed discoloration and stunting may occur
• Infected plants can be asymptomatic

FACTORS FAVORING DEVELOPMENT

• Planting infected seed
• Aphid infestation

IMPORTANT FACTS

• Not thought to be common in Minnesota or North Dakota
• Virus is seedborne and aphid-vectored
• Commonly confused with herbicide injury and bean pod mottle virus

Additional Diseases (not known to occur in ND/MN)

Soybean rust

Phakopsora pachyrhizi (fungus)

Photo by S Markell, NDSU

FIGURE 1 – Pustules visible on leaf wrapped around finger (approximately 5 to 10X)
Photo: S. Markell, NDSU

Photo by S Markell, NDSU

 FIGURE 2 – Profuse sporulation and leaf chlorosis
Photo: S. Markell, NDSU

Photo by D Marlvick, U of MN

FIGURE 3 – Magnified pustules
Photo: D. Malvick, Univ. of Minnesota

AUTHORS: Sam Markell and Dean Malvick

SYMPTOMS

• Very small gray-green, tan and/or red-brown spots on leaves
• Very small pustules on underside of leaf (hand lens needed)
• Leaf chlorosis and defoliation may occur

FACTORS FAVORING DEVELOPMENT

• Proximity to areas that do not freeze (southern Florida, Louisiana, Texas)
• Storms traveling from south to north that may bring spores showers (for example, hurricanes)
• Prolonged leaf wetness and moderate temperatures

IMPORTANT FACTS

• Soybean rust has never been recorded in Minnesota or North Dakota
• Dry edible beans may be a host
• Can cause significant yield loss
• Commonly confused with bacterial pustule and other foliar diseases.

NDSU Extension Logo

MN Ext Logo

ND Soybean Council Logo

Soybean Council

Sours: https://www.ag.ndsu.edu/publications/crops/soybean-disease-diagnostic-series/
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  3. Funnymike number
  4. Valance grid windows
  5. Linen like towels

A Guide to Common Soybean Diseases in The Midwest

Sources:

Fungus foliage diseases of soybeans. PPD N. Reports on Plant Diseases. Integrated Pest Management. https://ipm.illinois.edu/. 
Thomas-Murphy, J. Alternaria leaf spot. Diseases of Soybeans. Field Crops. Cornell University. https://fieldcrops.cals.cornell.edu/. 
Geisler, L.J. Anthracnose. CROPWATCH. University of Nebraska – Lincoln. https://cropwatch.unl.edu/. 
Malvick, D. Anthracnose on soybean. University of Minnesota. https://extension.umn.edu/. 
Kelly, H.M. and Stewart, S. Soybean rust. Institute of Agriculture. The University of Tennessee https://guide.utcrops.com. 
Smith, D. Asian soybean rust. Wisconsin Field Crops Pathology. University of Wisconsin. https://fyi.extension.wisc.edu/. 
Coker, C., Hurst, K., Kirkpatrick, T., Rupe, J., Tingle, C., and Trent, M. Asian soybean rust. FSA Agricultural and Natural Resources. University of Arkansas. https://www.uaex.edu. 
Malvick, D. Bacterial blight of soybean. University of Minnesota. https://extension.umn.edu/. 
Faske, F., Kirkpatrick, T., Zhou, J., and Tzanetakis, I. Soybean diseases. Arkansas Soybean Production Handbook. Chapter University of Arkansas. https://www.uaex.edu/. 
Faske, F., Kirkpatrick, T., Zhou, J., and Tzanetakis, I. Soybean diseases. Arkansas Soybean Production Handbook. Chapter University of Arkansas. https://www.uaex.edu/. 
Giesler, L.J. Bacterial pustule. CROPWATCH. University of Nebraska. https://cropwatch.unl.edu./. 
Giesler, L.J. Bean pod mottle virus. CROPWATCH. University of Nebraska. https://cropwatch.unl.edu. 
Malvick, D. Bean pod mottle virus on soybean. University of Minnesota. https://extension.umn.edu/. 
Smith, D. Bean pod mottle virus. Wisconsin Field Crops Pathology. University of Wisconsin. https://fyi.extension.wisc.edu/. 
Westphal, A., Abney, T.S., and Shaner, G. Brown stem rot. Diseases of Soybean. BPW. Purdue University. https://www.extension.purdue.edu/.
Kelly, H.M. and Stewart, S. Cercospora leaf blight. Institute of Agriculture. The University of Tennessee https://guide.utcrops.com. 
Hershman, D.E.  Cercospora leaf blight in Kentucky. Plant Pathology Fact Sheet. PPFS-AG-S University of Kentucky. https://plantpathology.ca.uky.edu. 
Smith, D.  Cercospora leaf blight and purple seed stain of soybean. Wisconsin Field Crops Pathology. University of Wisconsin. https://fyi.extension.wisc.edu/. 
Melvick, D. Charcoal rot on soybean. University of Minnesota Extension. https://extension.umn.edu/. 
Hershman, D.E. Charcoal rot of soybean. Plant Pathology Fact Sheet. PPFS-AG-S University of Kentucky. http://plantpathology.ca.uky.edu. 
Soybean pod and stem blight. Integrated Crop Management. Iowa State University. https://crops.extension.iastate.edu/. 
Malvick, D. Stem canker on soybean. University of Minnesota Extension. https://extension.umn.edu/. 
Kleczewski, N. Stem canker on soybeans. Field Crops Disease Management. http://extension.udel.edu/. 
Kelly, H.M. and Stewart, S. Downy mildew. Institute of Agriculture. The University of Tennessee https://guide.utcrops.com. 
Faske, T. and Kirkpatrick, T. Downy mildew of soybean. University of Arkansas. https://www.uaex.edu. 
Kelly, H.M. and Stewart, S. Frogeye leaf spot. Institute of Agriculture. The University of Tennessee https://guide.utcrops.com. 
Faske, T. Soybean disease update and management: Frogeye leaf spot. University of Arkansas. http://www.arkansas-crops.com/. 
Nelson, B. Fusarium root rot. Soybean Diseases. North Dakota State University. https://www.ndsu.edu/. 
Thomas-Murphy, J. Fusarium wilt. Field Crops. Cornell College of Agriculture and Life Sciences. https://fieldcrops.cals.cornell.edu/. 
Soybean management guide. Clemson University. https://scsoybeans.org/. 
Padgett, G. Nematode management in soybean. Louisiana State University. https://www.lsuagcenter.com/. 
Mulrooney, R.P. Soybean cyst nematode. PP University of Delaware. https://extension.udel.edu/. 
Sisson, A. Phyllosticta leaf spot. Integrated Crop Management. Iowa State University. https://crops.extension.iastate.edu/. 
Phyllosticta leaf spot of soybean. Crop Protection Network. https://cropprotectionnetwork.org/. 
Malvick, D. Phytophthora root and stem rot on soybean. University of Minnesota. https://extension.umn.edu/. 
Smith, D. Phytophthora root and stem rot. Wisconsin Field Crops Pathology. University of Wisconsin. https://fyi.extension.wisc.edu/. 
Zitnick-Anderson, K., Markell, S., and Nelson, Jr., B. Pythium damping-off of soybean. PP https://www.ag.ndsu.edu. 
Allen, T. Soybean seedling disease identification: Pythium damping-off and root rot. Mississippi Crop Situation. Mississippi State University. http://www.mississippi-crops.com. 
Padgett, B. Red crown rot. Root & Lower Stem Diseases. Soybean Disease Atlas. LSU AgCenter. Louisiana State University. https://www.lsuagcenter.com/. 
Scott, K. and Dorrance, A. Rhizoctonia damping-off and root rot of soybeans. Ohioline. The Ohio State University. https://ohioline.osu.edu/. 
Kelly, H.M. and Stewart, S. Brown spot. Institute of Agriculture. The University of Tennessee https://guide.utcrops.com. 
Faske, T. and Kirkpatrick, T. Brown spot of soybean. University of Arkansas. https://www.uaex.edu. 
Kleczewski, N. Southern blight in soybeans. Field Crops Disease Management. University of Delaware. https://extension.udel.edu/. 
Faske, T. and Kirkpatrick, T. Southern blight of soybean. University of Arkansas. https://www.uaex.edu/. 
Zhou, J. and Tzanetakis, I.E. Soybean mosaic virus. University of Arkansas. https://www.uaex.edu. 
Mueller, D. Soybean vein necrosis virus identified in Iowa. Integrated Pest Management. Iowa State University. https://crops.extension.iastate.edu/. 
Byamukama, E., Dorrance, A., Jardine, D., Malvick, D., Markell, S., Nachappa, P., Sisson, A., and Sweets, L. Soybean vein necrosis virus. Soybean Disease Management. CPN Crop Protection Network. www.soybeanresearchinfo.com/. 
Zhou, J. and Tzanetakis, I.E. Soybean vein necrosis virus. University of Arkansas. https://www.uaex.edu/. 
Kelly, H.M. and Stewart, S. Southern stem canker. Institute of Agriculture. The University of Tennessee https://guide.utcrops.com. 
Spurlock, T. Sudden death syndrome of soybean found. Arkansas Row Crops. University of Arkansas. http://www.arkansas-crops.com. 
Kelly, H.M. and Stewart, S. Target leaf spot. Institute of Agriculture. The University of Tennessee https://guide.utcrops.com. 
Faske, T. and Kirkpatrick, T. Target spot of soybean. University of Arkansas. https://www.uaex.edu. 
Zhou, J. and Tzanetakis, I.E. Tobacco ringspot virus. University of Arkansas. https://www.uaex.edu. 
Malvick, D.  Sclerotinia stem rot (white mold) on soybean. University of Minnesota Extension. https://extension.umn.edu. 
Smith, D. White mold of soybean (Sclerotinia stem rot). Wisconsin Field Crops Pathology. University of Wisconsin-Madison. https://fyi.extension.wisc.edu.

(Sources verified 6/) 

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Sours: https://www.krugerseed.com/en-us/agronomy-library/a-guide-to-common-soybean-diseases-in-the-midwest.html
Soybean Leaf Diseases

Identification of Late-season Soybean Diseases

Sources:

Faske, T. and Kirkpatrick, T. Aerial blight of soybean. University of Arkansas. https://www.uaex.edu/.

Kelly, H.M. and Stewart, S. Southern stem canker. Institute of Agriculture. The University of Tennessee https://guide.utcrops.com. 
Hershman, D.E. Stem canker of soybean. Plant Pathology Fact Sheet. PPFS-AG-S University of Kentucky. http://plantpathology.ca.uky.edu.

Giesler, L.J. Bacterial diseases of soybean. G NebGuide. University of Nebraska. http://www.soybeanresearchinfo.com/.

Malvick, D.  Sclerotinia stem rot (white mold) on soybean. University of Minnesota Extension. https://extension.umn.edu/. 
Smith, D. White mold of soybean (Sclerotinia stem rot). Wisconsin Field Crops Pathology. University of Wisconsin-Madison. https://fyi.extension.wisc.edu/. 
Malvick, D. Stem canker on soybean. University of Minnesota Extension. University of Minnesota. https://extension.umn.edu/. 
Kleczewski, N. Stem canker on soybeans. Field Crops Disease Management. http://extension.udel.edu/. 
Geisler, L.J. Anthracnose. CROPWATCH. University of Nebraska – Lincoln. https://cropwatch.unl.edu/. 
Malvick, D. Anthracnose on soybean. University of Minnesota. https://extension.umn.edu/.
Westphal, A., Abney, T.S., and Shaner, G. Brown stem rot. Diseases of Soybean. BPW. Purdue University. https://www.extension.purdue.edu/. 
Melvick, D. Charcoal rot on soybean. University of Minnesota Extension. https://extension.umn.edu/. 
Hershman, D.E. Charcoal rot of soybean. Plant Pathology Fact Sheet. PPFS-AG-S University of Kentucky. http://plantpathology.ca.uky.edu. 
Kelly, H.M. and Stewart, S. Frogeye leaf spot. Institute of Agriculture. The University of Tennessee https://guide.utcrops.com. 
Faske, T. Soybean disease update and management: Frogeye leaf spot. University of Arkansas. http://www.arkansas-crops.com/.
Kelly, H.M. and Stewart, S. Target leaf spot. Institute of Agriculture. The University of Tennessee https://guide.utcrops.com. 
Faske, T. and Kirkpatrick, T. Target spot of soybean. University of Arkansas. https://www.uaex.edu/. 
Kelly, H.M. and Stewart, S. Southern stem canker. Institute of Agriculture. The University of Tennessee https://guide.utcrops.com. 
Coker, C., Hurst, K., Kirkpatrick, T., Rupe, J., Tingle, C., and Trent, M. Asian soybean rust. FSA Agricultural and Natural Resources. University of Arkansas. https://www.uaex.edu/.
Kelly, H.M. and Stewart, S. Brown spot. Institute of Agriculture. The University of Tennessee https://guide.utcrops.com. 
Faske, T. and Kirkpatrick, T. Brown spot of soybean. University of Arkansas. https://www.uaex.edu/. 
Kelly, H.M. and Stewart, S. Cercospora leaf blight. Institute of Agriculture. The University of Tennessee https://guide.utcrops.com. 
Hershman, D.E.  Cercospora leaf blight in Kentucky. Plant Pathology Fact Sheet. PPFS-AG-S University of Kentucky. https://plantpathology.ca.uky.edu.  
Kelly, H.M. and Stewart, S. Sudden death syndrome. Institute of Agriculture. The University of Tennessee. https://guide.utcrops.com. 
Spurlock, T. Sudden death syndrome of soybean found. Arkansas Row Crops. University of Arkansas. http://www.arkansas-crops.com. 
Kelly, H.M. and Stewart, S. Downy mildew. Institute of Agriculture. The University of Tennessee https://guide.utcrops.com. 
Faske, T. and Kirkpatrick, T. Downy mildew of soybean. University of Arkansas. https://www.uaex.edu/. Zhou, J. and Tzanetakis, I.E. Soybean mosaic virus. University of Arkansas. https://www.uaex.edu. Giesler, L.J. Bean pod mottle virus. CROPWATCH. University of Nebraska. https://cropwatch.unl.edu. 
Malvick, D. Bean pod mottle virus on soybean. University of Minnesota. https://extension.umn.edu/. 
Smith, D. Bean pod mottle virus. Wisconsin Field Crops Pathology. University of Wisconsin. https://fyi.extension.wisc.edu/.  
Mueller, D. Soybean vein necrosis virus identified in Iowa. Integrated Pest Management. Iowa State University. https://crops.extension.iastate.edu/. 
Byamukama, E., Dorrance, A., Jardine, D., Malvick, D., Markell, S., Nachappa, P., Sisson, A., and Sweets, L. Soybean vein necrosis virus. Soybean Disease Management. CPN Crop Protection Network. www.soybeanresearchinfo.com/. 
Zhou, J. and Tzanetakis, I.E. Soybean vein necrosis virus. University of Arkansas. https://www.uaex.edu/. 
Joyce, A. and Thiessen, L. Root knot nematode of soybean. Soybean disease information. North Carolina State Extension. North Carolina State University. https://content.ces.ncsu.edu/.

Web sites verified 7/17/

_S1

Sours: https://www.channel.com/en-us/agronomy/identification-of-late-season-soybean-diseases-.html

Pictures soybean leaf diseases

Several diseases, including Phytophthora root and stem rot, pod and stem blight, frogeye leaf spot, brown spot, downy mildew, Cercopsora leaf blight and purple seed stain, and Sclerotinia stem rot (white mold), are known to affect soybeans in New York. Little is known, however, about the incidence, severity, or yield effects of diseases in the state. Diseases generally are kept in check by the use of sound agronomic practices such as crop rotation and the selection of soybean varieties with resistance to diseases known to be a problem in the local area. Although there is little research information on which to base chemical disease control guidelines in New York, the following information on fungicides is included as a service to New York growers who may wish to apply fungicides.

Disease Management

Fungicidal Seed Treatment

Treatment of seed with protectant fungicides, professionally applied by the seed supplier, is recommended for all soybean seed planted in New York - with the exception of organic production. Fungicide treatment is especially needed when seeds are planted into cold wet soils or where there is a field history of damping-off or Phytophthora root rot. Planting of bin-run seed is discouraged, though planter box application of fungicide can be made by the grower at the time of seeding. Remember to read and follow pesticide labels carefully.

Foliar Fungicides

Several fungicide products are registered for use on soybeans by foliar application. The efficacy of these products for soybean disease control based on appropriate application timing and labeled rates is listed in Table as a convenience for New York soybean producers. While each of the diseases listed occurs in the state, the data on the relationships between disease severity, yield loss, and economic return are not sufficient to base a recommendation for fungicide application to soybeans in New York. Good data from other parts of the United States, however, indicate that foliar fungicide application to a soybean seed crop (where environmental conditions and local disease pressure warrant it) can substantially increase seed vigor and germinability and can reduce the carryover of inoculum of seedborne diseases such as pod and stem blight and anthracnose.

Table

FungicidesAerial web blightAnthacnoseBrown spotCercospora leaf blight 2Frogeye leaf spot 3Pod and stem blightSoybean rustWhite mold 4Harvest restriction 5
ClassActive ingredient (%)Product/Trade nameRate/A (fl oz)
QoI Strobilurins Group 11Azoxystrobin %Quadris SCVGVGGFP-6G-VGPGrain: 14 days; forage/hay: 0 days
Fluoastrobin %Evito SCVGGGFP-6-6NLR5 (beginning seed); forage: 3 days; seed: 30 days
Picoxystrobin*^Approach SCVGGGFP-6GG14 days
Pyraclostrobin %Headline EC/SCVGVGGFP-6VGNL21 days
DMI Triazoles Group 3Cyproconazole %Alto SL-6-6VGF6F-6VGNL30 days
Flutriafol %Topguard SC7-6VGVGFVG-6VG-EF21 days
Propiconazole %Tilt EC Multiple GenericsPVGGNLFNLVGNLR5 (beginning seed)
Prothioconazole %Proline SC 8NLNLNLNLG-VGNLVGF21 days
Tetraconazole %Domark ME Multiple GenericsNLVGVGFG-6VG-EFR5 (beginning seed)
MBC ThiophanatesThiophanate-methylTopsin-M Multiple Generics-6-6-6FVG-6GF21 days
SDH1 Carboximides Group 7Boscalid 70%Endura DF-6NLVG-6PNLNLVG21 days
Mixed Mode of Actionazoxystrobin % difenconazole %Quadris Top -6-6-6-6VG-6VGNL14 days
azoxystrobin % propiconazole %Avaris SC Quilt SC-6-6G-6F-6VGNLR6
azoxystrobin % propiconazole %Quilt Xcel SEEVGGFF-6VGNLR6
cyproconazole % picoxystrobin %*§Aproach Prima SC 7,12-6-6-6-6G-6-6NLGrain: 30 days; forage/hay: 14 days
puraclostrobin % fluxapyroxad %*§Priaxor SC 7,12EVGEFF-6VGP21 days
tetraconazole % azoxystrobin %td>Affiance SC-6-6-6-6-6-6-6-614 days
trifloxystrobin % prothioconazole %Stratego YLD SC 9,10VGVGVGFF-6VGNL21 days
* This information was adapted for New York by Gary C. Bergstrom, Cornell University, from information developed by the North Central Regional Committee on Soybean Diseases and the Regional Committee for Soybean Rust Pathology (NCERA and NCERA) on foliar fungicide efficacy for control of major foliar soybean diseases in the United States. Efficacy ratings for each fungicide listed in the table were determined by field-testing the materials over multiple years and locations by the members of the committee. Efficacy ratings are based upon level of disease control achieved by product, and are not necessarily reflective of yield increases obtained from product application. Efficacy depends upon proper application timing, rate, and application method to achieve optimum effectiveness of the fungicide as determined by labeled instructions and overall level of disease in the field at the time of application. Differences in efficacy among gungicide products were determined by direct comparisons among products in field tests and are based on a single application of the labeled rate as listed in the table, unless otherwise noted. Table includes fungicides available that have been tested over multiple years and location. The table is not intended to be a list of all labeled products 2 Efficacy categories: NR=Not Recommended; P=Poor; F=Fair; G=Good; VG=Very Good; E=Excellent; NL=Not Labeled for use against this disease. Many products have specific use restrictions about the among of active ingredient that can be applied within a period of time or the among of sequential applications that can occur. Please read and folloe all specific use restrictions prior to fungicide use. This information is provided only as a guide. It is the responsibility of the pesticide applicator by law to read and follow all current label directions. Reference to products in theis publication is not intended to be an endorsement to the exclusion of others that may be similar. Persons using such products assume responsibility for their use in accordance with current directions of the manufacturer. Members of participants in the NVERA or NCERA group assume no liability resulting from the use of these products.
1 Some fungicides not in this table may be labeled for soybean rust only, powdery mildew, and Alternaria leaf spot. Contact fungicides such as chlorothalonil may also be labeled for use.
2 Cercospora leaf blight efficacy relies on accurate application timing, and standard R3 application timings may not provide adequate disease control. Fungicide efficacy may improve with later applications.
3Fungicides with a solo or mixed QoI mode of action may not be effective in areas where QoI-resistance has been detected in the fungal populationthat causes frogeye leaf spot. In areas such as New York where QoI-fungicide resistant isolates of the frogeye leaf spot pathogen have not been detected, QoI fungicides may be more effective than indicated in this table.
4 White mold efficacy is based on an R1 application timing, and lower efficacy is obtained at an R3 application timing, or if disease symptoms are already present at the time of application.
5Harvest restrictions are listed for soybean harvested for grain. Restrictions may vary for other types of soybean (edamame, etc.) and soybean for other uses such as forage or fodder.
6Insufficient data is available at this time to make statements about efficacy of these products for diseases listed in the table.
7No sale, use, or distribution in Nassau or Suffolk Counties in New York.
8Proline has a supplemental label (2ee) for soybean, only for use on white mold in IL, IN, IA, MI, MN, NE, ND, OH, SD, WI. A separate 2ee for New York exists for white mold.
9Stratego YLD has a supplemental label (2ee) for white mold on soybean, only in IL, IN, IA, MI, MN, NE, ND, OH, SD, WI, but not in New York.
10Aerial application is not allowed in New York.
11No application is allowed withing feet of coastal marsh.
12No application is allowed withing feet of aquatic habitats.
Sours: https://cals.cornell.edu/field-crops/soybeans/diseases-soybeans
Identifying Septoria Leaf Spot in Soybeans

Foliar Diseases of Soybeans

Published Feb. |Id: EPP

Introduction

Foliar diseases that attack the leaves are often observed on soybeans grown in Oklahoma. These diseases are caused primarily by fungi and bacteria. The damage caused by foliar diseases is mostly of minor importance. However, some diseases such as frogeye leaf spot and soybean rust can reduce yields when they develop early in crop development and weather conditions favor disease development.  Correct identification and early detection are critical in the proper management of soybean diseases. This fact sheet is intended to aid soybean producers in recognizing the diseases that commonly attack soybean foliage. Diseases and nematodes that attack seedlings and roots are described in Extension Fact Sheet EPP, and disease that attack stems and pods are covered in EPP Help in disease diagnosis can be obtained by submitting samples to the OSU Plant Disease and Insect Diagnostic Laboratory through local Cooperative Extension offices.

 

Bacterial Blight (Pseudomonas syringae pv. glycinea)

Bacterial blight is the most common bacterial disease of soybeans. This disease rarely causes yield loss, but it occasionally causes defoliation. Bacterial blight is favored by cool rainy weather, and is generally more prevalent early in the growing season. Dry and hot weather slows the development of this disease. Initial infections may occur during seedling emergence, with secondary disease outbreaks often following windy rainstorms or crop cultivation while the foliage is wet.

 

Foliar symptoms begin as small, water-soaked spots that turn yellow and then dark brown to black with a yellow border (Figure 1). The spots often coalesce to form irregular brown patches. Portions of the infected area may fall out, giving the leaves a ragged appearance.

 

Control is obtained by planting disease-free seed, ro- tating crops, and avoiding cultivation during times when the soybean foliage is wet.

A leaf showing bacterial blight.

 

 

Figure 1. Bacterial blight.

 

 

 

 

 

Bacterial Pustule (Xanthomonas campestris pv. glycines)

Bacterial pustule is another bacterial disease that is common in Oklahoma, but rarely becomes a significant problem. One difference between bacterial pustule and bacterial blight

 

is that bacterial pustule development is not reduced by high temperature. Consequently, bacterial pustule can develop throughout the growing season whenever wet conditions occur. Severe development of this disease can cause defoliation.

 

Symptoms of bacterial pustule consist of small yellow spots with reddish-brown centers (Figure 2). Later, in the center of the spots, a small raised pustule develops, which is most noticeable on the under-side of the leaf. Infections are common on younger leaves which are more susceptible than older leaves. Bacterial pustule is easily mistaken for soybean rust, a potentially more damaging disease.

 

Methods of control for bacterial pustule are the same as those suggested for bacterial blight. In addition, resistant varieties do exist and should be planted in areas that have a history of bacterial pustule problems.

A leaf with bacterial pustule.

 

 

Figure 2. Bacterial pustule (Photo courtesy A. Sisson, Iowa State Univ., Bugwood.org ).

 

 

 

 

Brown Spot (Septoria glycines)

Brown spot is the most common foliar disease of soybeans in Oklahoma. The disease is caused by a fungus that is spread by splashing rain. It frequently occurs following rainy periods early in the growing season, but rarely increases during late season.  Hot, dry weather limits the development of this disease. If conditions favorable for disease development continue into the season or reoccur before maturity, the resulting defoliation can cause yield loss.

 

The first unifoliate leaves and lower trifoliate leaves typically show symptoms of brown spot. The reddish brown lesions vary in size from pinpoint to 1/4 inch in diameter, but may merge and form larger irregular shaped spots (Figure 3). Severely infected leaves turn yellow and fall from the plant. Defoliation begins in the lower canopy and moves upward as the disease progresses.

 

Incidence of this disease is reduced by managing soybean crop residue, rotating crops (at least 1 year out of soybeans), and planting high quality seed. Fungicide applied to foliage during reproductive stages of crop development typically does not provide good control of brown spot because the disease develops earlier in the growing season.

A leaf with brown spots.

 

 

Figure 3. Brown spot.

 

 

 

 

Downy Mildew (Peronospora manshurica)

Downy mildew is a common foliar disease of soybeans, but it rarely causes serious damage. The development of this disease is favored by high humidity and cool temperatures. The increased resistance of older leaves and high temperatures slow the development of downy mildew during mid-season, and extensive disease development rarely occurs.

 

Downy mildew appears on the upper surface of young leaves as pale green to light yellow spots. As the spots enlarge, they become pale yellow and of irregular size and shape (Figure 4). During periods of high humidity, a white to tan colored tuft of moldy growth often develops on the undersides of the spots. The spots eventually turn tan in color as they die. Rarely does downy mildew progress to levels high enough to cause defoliation.

 

Because the damage from downy mildew is mostly cosmetic, management practices are not required.

A leaf with downy mildew.

 

 

Figure 4. Downy mildew.

 

 

 

 

 

Frogeye Leaf Spot (Cercospora sojina)

Frogeye leaf spot is a foliar disease of soybeans that has the potential to cause significant yield loss. This disease is most severe during seasons with frequent rainfall and long periods of high relative humidity.

 

Young expanding leaves are extremely susceptible to infection, while fully expanded leaves are relatively resistant. However, the symptoms of frogeye leaf spot develop nearly two weeks after initial infection; therefore, lesions are never seen on young expanding leaves. Leaves that expand during periods of weather unfavorable for infection remain relatively disease free which can result in alternating layers of healthy leaves and diseased leaves.

 

Spots develop on the upper surface of leaves that measure up to 1/4 inch in diameter, but may coalesce to form larger spots. Young, fully developed spots have a gray to brown center with a distinct purple to reddish-brown margin (Figure 5). As lesions age, the center becomes tan to nearly white, and the margin darkens. Severe levels of disease cause blighting of foliage.

 

Crop rotation and management of old crop residues reduces disease incidence. Varieties with resistance to frogeye leaf spot should be selected. Fungicides applied at first pod (R3) and beginning seed (R5) growth stages will protect against yield loss from frogeye leaf spot on susceptible varieties.

A leaf with frogeye leaf spot.

 

 

Figure 5. Frogeye leaf spot.
 

 

 

 

 

Cercospora Leaf Blight (Purple Seed Stain) (Cercospora kikuchii)

Cercospora leaf blight is a late season disease that is often mistaken for early senescence. This disease attacks seeds, pods, stems, and leaves; however, there is no consistent correlation between the development of foliar symptoms and the occurrence of stained seed.

 

The disease is easily identified through the discoloration of the seed and is commonly called purple seed stain. Seed discoloration varies from pink or pale purple to dark purple (Figure 6). The stained areas range in size from small specks to large irregular blotches, which may cover the entire surface of the seed coat.

 

Foliar symptoms begin to appear at the beginning of pod fill and develop initially as small, reddish-purple, angular to irregular lesions on the upper leaf surface. As the disease progresses, the infected leaves become leathery, and the upper surface of the leaf develops dark purplish-red to bronze discoloration (Figure 7). Heavily infected leaves rapidly turn yellow and drop from the plant, mimicking natural leaf fall. Lower leaves remain green and attached to the plant.

 

Although some soybean varieties are resistant, control is usually achieved by planting disease-free seed. In fields with a history of purple seed stain problems, the application of foliar fungicides during early pod set (R3 to R4) should aid in the control of this disease and may improve seed quality.

Purple seed stain.

 

 

Figure 6. Purple seed stain.

 

 

 

 

A leaf with cercospora leaf blight.

 

 

Figure 7. Cercospora leaf blight.

 

 

 

 

 

Soybean Rust (Phakopsora pachyrhizi)

Since it was first discovered in the U.S. in , soybean rust has occurred sporadically in Oklahoma. Because the disease requires living plants (soybeans or kudzu) to survive, it can only overwinter in tropical and sub tropical climates. It must move northward each year from areas where vegetation does not freeze such as Florida, south Texas, and Mexico. The northward progress of soybean rust is affected by cropping systems and weather conditions during the growing season. The disease is favored by wet and cloudy weather. Hot (>90F) and dry weather slows the progression soybean rust and the damage it causes. Therefore, the disease often does not reach Oklahoma early enough to cause significant damage, if at all. Nevertheless, soybean rust is a damaging disease that can reduce yield where it becomes established during early reproductive stages of crop development.

 

Symptoms of soybean rust first appear as pale green to yellow flecks on leaves in the low to mid canopy of plants in the reproductive stages of crop development. Spots become angular in shape and reddish brown in color (Figure 8). Spots remain small, but become numerous. Soybean rust can easily be confused with bacterial blight, bacterial pustule, and brown spot. A key feature of soybean rust is the raised pustules (pimples) on the underside of spots visible through a hand lens. Tufts of tan colored spores may also be seen emerging from the pustules.

 

The only effective management strategy is to make one or two applications of fungicide to the foliage during the reproductive stages of crop development where the disease has been identified or threatens.

A leaf with soybean rust.

 

 

Figure 8. Soybean rust.

 

 

 

 

 

Use of Foliar Fungicides

The Oklahoma Cooperative Extension Service does not routinely recommend the application of foliar fungicides to control foliar, pod, and stem diseases of soybeans. Research conducted in Oklahoma has shown that although fungicides are capable of reducing the incidence and severity of these diseases, they are not consistently effective in increasing soybean yields except where frogeye leaf spot or soybean rust become severe. However, foliar fungicides have been shown to routinely improve seed quality in years in which warm weather and frequent rains occur during the reproductive stages of soybean development. Consult the Soybean Production Guide (Extension Circular E) or the Extension Agent’s Handbook of Insect, Plant Disease and Weed Control (Extension Circular E), available at your local County Extension office for more information on fungicides recommended for use on soybeans.

 

Disease Management Principles

A basic strategy for control of foliar soybean diseases is prevention. The following suggestions are offered in an attempt to provide soybean producers some basic components that will aid in the prevention of soybean diseases.

  • Plant high quality seed.
  • Apply fungicide seed treatment.
  • Use proper seed bed preparation, planting depth, and seeding rates.
  • Practice crop rotation with non-legume crops.
  • Scout soybeans regularly to detect disease problems early.
  • Plant disease and nematode resistant varieties.
  • Apply fungicide to foliage when frogeye leaf spot and/or rust threaten.
  • Practice good management of soil fertility, weeds, and insects.

Integrating the above principles, as they apply, into a soybean production program will help prevent diseases from becoming a limiting factor.

 

References

Colyer, P.D. (ed) Soybean Disease Atlas, 2nd Ed. As-sociated Printing Professionals, Inc., 43 pp.

 

Hartman, G.L., J.B. Sinclair, and J.C. Rupe (eds). Compendium of Soybean Diseases, 4th Ed. APS Press, St. Paul, pp.

 

Pratt, P., P. Bolin, and C. Godsey (eds). Soybean Production Guide. OCES Circular E, pp.

 

John Damicone

Extension Plant Pathology Specialist

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