Diagnosing Interveinal Chlorosis in Soybeans — it's not just SDS

Updated in 2026, this version replaces the 2019 Diagnosing Interveinal Chlorosis in Soybeans— it's not just SDS (Archived) publication.

Interveinal chlorosis, the term used for yellowing and browning of tissue between leaf veins in the upper soybean canopy, is a common symptom in soybean production (Figure 1). More often than not, it is assumed that interveinal chlorosis indicates the presence of soybean sudden death syndrome (SDS).

However, there are several additional diseases and disorders that can cause interveinal chlorosis in soybean besides SDS. Some of these diseases are new to the U.S. and Canada, or are expanding into new regions, which can complicate disease diagnosis. This article will discuss the most common diseases and disorders associated with interveinal chlorosis of soybean leaves.

Brown stem rot

Brown stem rot (BSR) is a disease caused by the soilborne fungus, Cadophora gregata, which often produces interveinal chlorotic leaf symptoms typically observed in the mid to upper canopy. These symptoms are usually noticed in the mid to late reproductive stages of soybean (R3 and later). Entire plants with foliar symptoms should be removed from the soil carefully and stems split to observe the internal stem tissue. Soybean stems affected by BSR will have brown pith tissue, especially near nodes (Figure 2). Roots will be healthy and not rotted. It is important to note that there are two strains (genotypes) of the fungus that causes BSR. Only the ‘A’ genotype causes typical interveinal chlorosis, while the ‘B’ genotype does not. Both genotypes cause the pith to turn brown. The geographic area can also help with identifying BSR. This disease is primarily observed in northern soybean growing regions, and is rarely, if ever, diagnosed in the Mid-South and southern states. Planting resistant soybean varieties (especially those with soybean cyst nematode resistance) and rotation to a non-host crop for two years or more are management options for BSR.

Stem canker

Stem canker in soybean is caused by two soilborne fungi, Diaporthe aspalathi and Diaporthe caulivora. These fungi can produce different foliar symptoms on infected plants (Figure 3). Diaporthe aspalathi may cause interveinal chlorosis, while D. caulivora typically results in wilted leaves or plant death but does not usually cause interveinal chlorosis. These two fungi are widely distributed throughout the U.S., and are not geographically confined, as was previously thought. Therefore, plants exhibiting interveinal chlorosis in any state may be affected by the pathogen causing stem canker and should be submitted to diagnostic laboratories for accurate diagnosis. The symptoms associated with stem canker can begin shortly after flowering (R1), and are observed through R6. Both stem canker fungi can cause reddish brown, sunken lesions on the outside of the stem (Figure 4). These lesions are often associated with nodes and spread up the stem. Roots of plants affected with stem canker may appear healthy. Research is ongoing to better understand stem canker management. At this time, variety resistance and crop rotation are the most viable management options. For more information see the CPN publication Stem Canker (CPN 1006).

Sudden death syndrome

Sudden death syndrome (SDS) is primarily caused by the soilborne fungus Fusarium virguliforme. This fungus produces a toxin that moves into the leaves, causing the characteristic interveinal chlorosis that is often the first indication of SDS (Figure 5). Symptoms are most commonly observed in the mid to late reproductive stages (R3 and later). Symptoms begin as yellow spots between leaf veins which expand and turn brown, leading to interveinal chlorosis. Symptoms are most pronounced  in the youngest leaves, which often die and fall prematurely, leaving petioles attached to the stem. SDS can result in plants with rotted roots, and the cortex of the stem will be brown or gray, while the pith remains white. Integrated management of SDS is important. Variety resistance, certain fungicide seed treatment active ingredients, and soybean cyst nematode management can all help manage SDS. For more information see the CPN publication Sudden Death Syndrome (CPN 1011).

Taproot decline

Taproot decline is caused by the soilborne fungus Xylaria necrophora. It causes interveinal chlorosis of plants beginning in the mid-vegetative (V4-V6) that becomes more commonly observed during advanced reproductive growth stages  (R5-R6.5). Symptomatic leaves are often first observed in the lower canopy, and increase in severity as the season progresses (Figure 6). Affected taproots  are dry, brittle, rotted, often with black fungal growth. When plants are pulled, the root systems often break off, and exposed taproots appear dark with brown internal discoloration, and snap easily. In certain conditions (i.e., moist environments), fungal structures  known as “dead man’s” fingers can be observed on residue that remains on the soil surface or from buried residue  While the geographical distribution of taproot decline is not fully known, it has been reported in Alabama, Arkansas, Louisiana, Mississippi and as far north as southern Missouri and Tennessee. Currently, management options are unknown, but research is underway to determine the impact and management for this disease.

Triazole fungicide injury

Application of fungicides in the demethylation-inhibiting class known as triazoles (Fungicide Resistance Action Committee Group 3) can cause injury or a phytotoxic effect that results in interveinal chlorosis on soybean leaves (Figure 7). Symptoms only appear on leaves, typically in the upper canopy, and stems and roots remain healthy. Injury is worse when certain triazole fungicides are applied during hot and dry conditions and can appear more injurious in situations where certain adjuvants are applied at rates equal to or exceeding 0.25% (v/v). Triazole fungicide injury is more commonly observed in the southern or Mid-South production regions due to the environmental conditions that favor injury; however, reports of phytotoxicity occurred as far north as Iowa during the 2018 season. Fungicide products that contain prothioconazole or tebuconazole are much more prone to producing phytotoxicity. In addition, the injury associated with this disorder is generally observed 21 to28 days following the application of a fungicide that contains a triazole in either a pre-mix product or a tank-mix combination. Soybean varieties vary in their response to triazole fungicide injury, which can confuse diagnosis. Yield losses due to triazole fungicide injury have not been observed; however, research continues to determine the role of the injury as well as potential methods to reduce the injury observed.

Red crown rot

Red crown rot (RCR) has increased in distribution across soybean-producing states and is caused by the soilborne fungus Calonectria ilicicola. RCR can cause interveinal chlorosis and necrosis, commonly observed at or after R3 (Figures 8 and 9). Affected plants often show reddish discoloration of the lower stem and roots, which can appear as early as vegetative stages, along with extensive root rot by the end of the season (Figure 10). Leaves may die prematurely but typically remain attached to the petioles, and the pith of the lower stem may appear gray when split. Late in the season, the fungus may produce small (less than 1/16 inch, about 2 mm) reddish-orange spherical structures (perithecia) on the lower stem and roots, which help distinguish RCR from other causes of interveinal chlorosis. Management should prioritize the use of registered seed treatments for RCR suppression and sanitation practices, including washing equipment to avoid moving infested soil and residue from field to field.

Additional diseases that produce interveinal chlorosis

There are several additional soybean diseases that may temporarily cause interveinal chlorosis depending on the environment, variety, or geographic location. These diseases include southern blight, Phytophthora root and stem rot, and white mold (Figure 11). If these diseases are the cause of the interveinal chlorosis, leaves will eventually turn brown and the interveinal chlorosis symptoms can no longer be observed.

In all cases discussed here, a field diagnosis should not simply rely on foliar symptoms. Stem and root symptoms of plants exhibiting interveinal chlorosis can help distinguish among these diseases and disorders. When the cause of the interveinal chlorosis is unclear, plant samples should be sent to a diagnostic laboratory to get an accurate diagnosis.

Acknowledgements

Authors

Kiersten Wise, University of Kentucky; Tom Allen, Mississippi State University; Boris X. Camiletti, University of Illinois Urbana-Champaign; Febina Mathew, North Dakota State University; and Daren Mueller, Iowa State University.

Reviewers

Travis Faske, University of Arkansas and Andrew Friskop, North Dakota State University

Sponsors

The authors thank the United Soybean Board and the United States Department of Agriculture - National Institute of Food and Agriculture (USDA-NIFA) for supporting Crop Protection Network infrastructure and resources. 

How to cite: Wise, K., Allen, T., Camiletti, B., Mathew, F., and Mueller, D.. Diagnosing Interveinal Chlorosis in Soybeans — it’s not just SDS. 2026. Crop Protection Network. CPN-1023. doi.org/10.31274/cpn-20190826-000.