For nearly 40 years, sudden death syndrome (SDS) has ranked second only to soybean cyst nematode (SCN) in damage to soybean crops. DuPont Pioneer research shows that, in extreme conditions, this root-rotting disease can cause yield losses as high as 80 percent.
"SDS varies in severity from area to area, and from field to field, but as a result of the cool, moist soil conditions earlier this season there may be a higher incidence of SDS in soybeans this year," says Jeff Thompson, DuPont Pioneer senior research manager.
Disease severity depends on environmental conditions, time of infection and other stresses on the soybean crop. This year may result in a higher incidence of SDS in soybeans as a result of cool, moist soil conditions early in the growing season. Though SDS infects soybean plants just after germination and emergence, symptoms usually do not appear until midsummer.
Symptoms
The development of symptoms is often linked with weather patterns of cool wet conditions early on followed by warm temperatures and high rainfall during flowering or pod-fill.
"Symptoms begin as small pale-green spots during flowering, just before pod-fill," Thompson says. "And the most visible symptoms will occur as necrotic lesions during pod-fill, when plants are focused on water uptake and sending nutrients to the developing seed."
Usually observed 10 to 14 days after heavy rains, root symptoms include rotted roots with deteriorated taproots and lateral roots. The root cortex will show light-gray to brown discoloration, and if soil moisture is high, sometimes bluish fungal colonies are present. These symptoms signal reduced water and nutrient uptake by the plant.
Leaf symptoms of SDS first appear as yellow spots, usually in a mosaic pattern on the upper leaves. The yellow spots coalesce to form chlorotic blotches between the leaf veins and the affected leaves will twist and curl before falling from the plant prematurely.
Source: Pioneer