A blue coloration may be found on the outer surface of taproots due to the large number of spores produced
These fungal colonies may not appear if the soil is too dry or too wet
Splitting the root reveals cortical cells have turned a milky gray-brown color while the inner core, or pith, remains white
General discoloration of the outer cortex can extend several nodes into the stem, but its pith also remains white
Facts
Leaf and Plant Symptoms
Leaf symptoms first appear as yellow spots (usually on the upper leaves) in a mosaic pattern
Yellow spots coalesce to form chlorotic blotches between the leaf veins
As chlorotic areas die, leaves show yellow and brown areas contrasted against green veins
Affected leaves twist and curl and fall from plants prematurely
Flowers and pods abort, and seeds are smaller
Later-developing pods may not fill, and seeds may not mature
Disease Facts
Fungal disease caused by Fusarium virguliforme
Has spread to most soybean-growing states and Ontario, Canada
Continues to spread to new fields and larger areas of infected fields
Ranked second only to soybean cyst nematode (SCN) in damage to soybean crop
Fungus colonizes only crown and roots of the plant
Above-ground symptoms are caused by a toxin produced by the fungus and translocated throughout the plant
Severity varies from area to area and field to field
Favorable Conditions
Conditions Favoring Disease Development
Cool, moist conditions early in the growing season often result in higher disease incidence
Favorable disease conditions may result from early planting, high rainfall and/or low-lying, poorly drained or compacted field areas
If SCN is also a problem in the field, disease may be more severe
Infection occurs early in the season, but symptoms usually do not appear until midsummer
Appearance of symptoms often associated with weather patterns of cooler temperatures and high rainfall during flowering or pod fill
Disease Cycle
Fungus survives in crop debris and as mycelia in the soil
Survives best in wet areas such as poorly drained or compacted field areas
Fungus enters roots early in the growing season
Infection may be facilitated by wounds from SCN, insects or mechanical injury
Fungus colonizes the root system
Fungus overwinters in diseased soybean residue
Impact on Crop
Soybean seed yield is reduced as:
Plants lose leaf area and leaves drop prematurely
Roots deteriorate, reducing water/nutrient uptake
Flowers and pods abort, resulting in fewer pods and seeds
Seeds may be smaller and late-forming pods may not fill or mature
Management
Management of Sudden Death Syndrome
Use a combination of practices:
Select SDS-resistant varieties
Pioneer has developed elite soybean varieties with improved SDS resistance
Soybean breeders have selected for genetic resistance in multiple environments with high levels of natural SDS infection
Pioneer rates its varieties and makes ratings available to customers
Ratings range from 4 to 8 (9 = resistant), indicating very good resistance is available in elite soybean varieties
Your Pioneer representative can help you select suitable varieties
Manage soybean cyst nematode (SCN)
Plant varieties resistant to both SDS and SCN
Improve field drainage and reduce compaction
Evaluate tillage systems
Where possible, some tillage may be needed to bury infected residue
Reduce other stresses on the crop
Plant the most problematic fields last in your planting sequence
Foliar fungicide cannot protect plants from SDS
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