Issue No. 21, Article 4/August 15, 2008
Sudden Death Syndrome Symptoms Beginning to Appear in Soybean
Symptoms of sudden death syndrome of soybean (SDS; caused by the fungus Fusarium virguliforme, formerly known as Fusarium solani f. sp. glycines) are beginning to appear in some soybean fields in Illinois. Initial symptoms appear as light-yellow flecking on the leaves. The yellow areas enlarge to cause interveinal chlorosis (yellow leaves with the veins remaining green) and eventually interveinal necrosis (dead leaves with the veins remaining green). These foliar symptoms generally do not appear until the soybean plants are into the reproductive growth stages (July and August).
Although SDS symptoms appear on the foliage of the plants, the Fusarium fungus that causes SDS actually infects the soybean roots early in the growing season. The foliar symptoms of SDS are caused by a toxin that the fungus produces, and the toxin then moves upward in the vascular system of the plant.
Initial foliar symptoms of sudden death syndrome appear as yellow flecking on the leaves.
Interveinal chlorosis and necrosis of soybean leaves with sudden death syndrome.
Unfortunately, there are no silver bullets available to control SDS completely, so using multiple management practices is encouraged to help limit its damage:
- Variety choice. One of the most important SDS management decisions can be made before the growing season begins. Although there are no soybean varieties with complete resistance to SDS, differences in susceptibility do exist. Many seed companies provide SDS-resistance ratings for their soybean varieties. Also, many soybean varieties are rated for SDS by University of Illinois, Southern Illinois University, and USDA-ARS personnel in field and greenhouse trials as part of the Illinois VIPS (Varietal Information Program for Soybeans) program. The results of these trials are available at web.aces.uiuc.edu/VIPS.
- Planting date. Early planting may predispose soybean plants to infection by the SDS fungus. Plant fields with no history of SDS first and those with a history of SDS last.
- Soil compaction and drainage. Soils with compaction and/or drainage problems may lead to bigger problems with SDS. Management practices that alleviate soil compaction and drainage problems in a field may also help limit losses from SDS.
- Interaction with soybean cyst nematode. Although it is not always easy to prove in research trials that have been conducted, there appears to be an interaction between SDS and the soybean cyst nematode. If both are present in a field, then yield losses may be more dramatic than if either one were present alone. Good management practices for SCN will certainly reduce losses due to SCN, and they may also provide some benefits with SDS management.--Carl A. Bradley
Carl A. Bradley