Purdue University

• Can be seen in late vegetative stages
• Stunting, mottling and curling of leaves
• leaves may be puckered and misshapen
• Diseased pods may be stunted and curved
• Seeds from diseased pods may be discolored

Other info

• Resembles 2, 4-D injury
• A common disease, but rarely causes significant yield losses

Conditions that may cause soybean mosaic virus

• Cool, dry conditions

Purdue University

 

• Can be seen in early flowering stages
• Slight to severe stunting and chlorosis
• Decreased nodulation
• Slow closing canopy
• Some root decay
• Cysts on roots first appear as white lemon- shaped females on root surface
• Cysts turn dark brown with age
• Foliar symptoms are similar to nitrogen and/or potassium deficiency

Conditions that may cause Soybean cyst nematode

• Symptoms are more pronounced under dry soil or stress conditions
• can occur in any soil type
• normally more pronounced in light soils or sandy soils

Purdue University

 

• Can be seen all season (Following rain)
• Small Angular water soaked spots on leaves.
• Lesions with centers that dry out and turn brown to black.
• Affected tissue may drop off, causing the leaf to look tattered.

Conditions that may cause Bacterial blight

• Cool, rainy weather
• outbreaks often follow thunderstorms

Purdue University

 

• Can be seen during mid- to late- flowering
• Irregular light-brown lesions that range in size from a small speck to a few mm in diameter
• Lesions will eventually turn to a brownish black
• Lesions normally appear on leaves but they can occur on the stems, petioles and pods

Conditions that may cause Brown spot

• Extended warm, wet weather

Purdue University

 

• Can be seen during mid- to late- flowering
• Pale green to yellow spots on upper leaf surface
• Lesions will turn to a grayish brown to dark brown color with a yellow or light green margin.
• Gray tufts of fungal growth may form on lower leaf surface
• Leaves with a sever affection can turn brown and drop off
• Where pods are present a whitish fungal growth may develop on the interior of the pods and seed coats

Other info

• Systemically infected seedlings from infected seeds are stunted and may have mottled foliage

Conditions that may cause Downy mildew

• High humidity
• Cool temperatures

Purdue University

 

• Can be seen during mid- to late- flowering
• Yellow interveinal blotches
• Blotches become necrotic leaving green tissue along the veins
• Leaf blades will drop off leaving petioles attached to stem
• Foliar symptoms similar to brown stem rot
• Internal taproot tissue will turn light brown to gray
• Pith of stem remains white

Conditions that may cause Sudden death syndrome

• Often occurs with soybean cyst nematode
• Soybean cyst nematode not necessary for Sudden death to occur
• Cool wet soils in early spring

Purdue University

• Can be seen during mid- to late- flowering
• Loss of vigor in mature plants
• Leaves turn yellow and wilt but do not drop off
• Taproot and lower stem will develop a light gray or silver color after flowering
• Small black fungal structures form in taproot and stem tissues

Conditions that may cause Charcoal rot

• High soil temperatures
• Dry weather
• Plants are most susceptible when under stress from environmental conditions

University of Kentucky

 

• Can be seen during late- flowering
• Slightly sunken brown lesions at the base of leaf nodes
• Lesions can expand into elongated reddish-brown sunken cankers
• Plant parts above cankers may die

Conditions that may cause Stem canker

• Fungus normally survives the winter in the seed
• Crop residue can also host fungus over the winter
• Wet weather favors disease

Purdue University

 

• Can be seen at pod fill
• Sudden discoloration of leaves
• Brown tissue between leaf veins with green tissue along veins
• Leaves remain attached
• Infected plants display a browning of the pith inside the stem

Conditions that may cause Brown stem rot

• Disease progresses faster in older plants regardless of temperature

 

Purdue University

• Can be seen at pod fill
• No definite leaf or stem lesions
• Fungal spore-bearing structures appear as black specks in linear rows on dead stems and poorly-developed pods.

Other info

• Pod blight phase results in poor quality seeds and seed decay
• Seedling blight may occur from seed infection

Conditions that may cause pod and stem blight

• Warm wet weather at R7 to R8 growth stages