Sudden death syndrome infects soybean plants just after germination and emergence – but symptoms typically don’t appear until midsummer. DuPont Pioneer is urging growers to scout for the disease now – noting that the cool, moist conditions earlier this season could result in a higher incidence of SDS in soybeans this year. This disease has ranked second only to soybean cyst nematode in damage to soybean crops for nearly 40 years. According to DuPont Pioneer research – in extreme conditions – SDS can cause yield losses as high as 80-percent. Senior Research Manager Jeff Thompson says SDS varies in severity from area to area and field to field. He says growers must understand clearly the extent of infection in each of their fields to effectively manage the disease – so scouting is essential.
Thompson says symptoms begin as small pale-green spots during flowering – just before pod-fill. He says 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. Root symptoms are usually observed 10 to 14 days after heavy rains and include rotted roots with deteriorated taproots and lateral roots. DuPont Pioneer notes the root cortex will show light-gray to brown discoloration and sometimes bluish fungal colonies are present if soil moisture is high. The leaf symptoms of SDS first appear as yellow spots 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.
Pioneer experts recommend several management options to combat the yield-robbing effects of SDS year after year. Management practices include selecting tolerant varieties, planting disease-prone fields last, improving field drainage, reducing compaction, maintaining proper fertility on fields, evaluating tillage systems and reducing other stresses on the crop. Thompson says growers should also scout for SCN because there’s a tendency for products susceptible to SCN to display more severe SDS symptoms.
For more SDS scouting tips and management options – visit www dot pioneer dot com (www.pioneer.com).