Soybean Diseases

Question 1

Asian Soybean Rust

Answer 1

Fungus on Soybean, Kudzu, maybe other legumes

Rust on leaves

windborne spores (long distance)

Favored by early arrival of windborne spores;
moderate temperatures; rain

Application of protectant fungicides prior to infection (1-2)
Timely application of fungicides with systemic, curative activity (1)

Question 2

Bacterial Blight

Answer 2

Bacterium on soybean

Lesions on leaves and pods

Spread by Rain-splashed bacteria from debris;
cultivation during wet periods

Favored by cool, wet weather

High quality seed (2)
Crop rotation (2)
Avoid highly susceptible varieties (2)

Question 3

Bacterial Pustule

Answer 3

Bacterium on soybeans

Lesions on leaves and pods

Spread by rain-splashed bacteria from debris;
culitvation during wet conditions

Favored by wet conditions

High quality seed (2)
Crop rotation (2)
Avoid highly susceptible varieties (2)

Question 4

Downy Mildew

Answer 4

Oomycete on soybeans

Mildew on leaves, pods, seeds

Spread by windborne sporangia;
systemic infection from infected seeds

Favored by high humidity and moderate temperatures

Crop Rotation (2)
Anti-oomycete seed treatment (2)

Question 5

Pod and Stem Blight

Answer 5

Fungus on soybean

Pod and stem lesions

Rain-splashed spores from infected soy debris

Favored by prolonged moist periods during pod maturation

Crop rotation (2)
Adapted varieties (2)
timely harvest (2)
late season foliar fungicides if warrented by disease pressure (2)

Question 6

Sclerotinia Stem Rot (White Mold)

Answer 6

Fungus of many dicots

Windborne spores from sclerotia on soil surface

Favored by dense canopy;
moisture at flowering;
disease of previous crop

Tolerant/Resistant varieties (2)
Crop rotation (2)
Wide row spacing (2)
Foliar fungicides (2)

Question 7

Septoria brown spot

Answer 7

Fungus

Spread by infected soybean debris:
Seedborne

Favored by splashing rain;
moist conditions;
soybean after soybean

Crop rotation (2)
Foliar fungicides if warrented by disease pressure (1)

Question 8

Soybean Cyst Nematode

Answer 8

Nematode only on soybean

Colonizes roots, stunts plants

In soil;
movement on equipment, unclean seed

Favored by infested local soil from which nematodes may be introduced to new fields

Avoid introduction (1)
Resistant varieties (1)
Crop Rotation (2)

Question 9

Soybean mosaic virus

Answer 9

Virus on soybean

Mosaic on leaves, stunted plants

Aphid-transmitted (nonpersistent) from infected live hosts;
seed transmitted

Favored by high aphid pops when plants are young

Plant virus free seed (1)
Timely planting (2)
Resistant varieties (strain specific) (2)