An Overview of Soybean Vein Necrosis Virus

Updated in 2026, this version replaces the 2015 An Overview of Soybean Vein Necrosis Virus publication.

Soybean vein necrosis virus (SVNV) is a member of the genus Orthotospovirus (Family Tospoviridae), a group of viruses capable of causing serious damage in many different crops. SVNV was recognized as being widely prevalent in soybeans across the United States and Ontario in 2012, although it may have been present in soybeans previously but overlooked. Accurate diagnosis of SVNV is important because it can be easily confused with other soybean diseases, disorders, or damage, potentially leading to unnecessary fungicide applications.

This publication examines the symptoms associated with SVNV, describes how SVNV differs from other plant problems with similar symptomology, and provides scouting information.

Symptoms

SVNV symptoms often first appear along field edges and are typically randomly distributed throughout the canopy of infected plants. Lesions initially develop as yellowing (chlorosis) along the leaf veins. Over time, yellowing becomes red-brown, irregular-shaped lesions, and eventually leads to tissue death (Figures 1 and 2). The yellowing around the lesion may begin to spread beyond the vein but will typically be limited to the area within other major leaf veins. The symptomatic lesions are generally not uniform across the leaf, and are presumed to be associated with previous feeding (sites) by thrips, the primary vectors of the virus.

Leaf tissue generally dies following chlorosis. Lesions typically spread along or from the edge of a vein. The irregular-shaped lesions range from 1⁄4 to 1⁄2 inch (6 to 12 mm) in diameter, but can be larger if adjacent lesions coalesce (Figure 3). In affected plants, the veins may appear clear, yellow, or dark brown. Vein discoloration may be more apparent on the undersides of leaves (Figure 4).

Anecdotal evidence indicates soybean varieties may differ in their response to SVNV infection, potentially due to feeding preferences of the soybean thrips (Neohydatothrips variabilis), the principal insect vector of this pathogen, or to differential levels of tolerance or resistance that have yet to be studied.

Problems With Similar Symptoms

Diseases

Several diseases produce symptoms that can be confused with those caused by SVNV. Accurate diagnosis of SVNV is essential to avoid unnecessary management actions that are ineffective against this disease.

Septoria Brown Spot (Septoria glycines)

Septoria brown spot causes dark brown lesions that are scattered on the upper and lower surfaces of leaves in the lower to middle canopy (Figure 5). Adjacent spots can coalesce and affected leaves may turn yellow and drop prematurely (Figure 6). Brown spot is a commonly occurring disease, especially in continuous soybean rotations. In addition, it is usually one of the first diseases to appear each year.

How to distinguish brown spot from SVNV: Brown spot lesions are mainly located in the lower canopy and are not associated with leaf veins like SVNV lesions.

Bacterial Blight (Pseudomonas savastanoi pv. glycinea)

Bacterial blight causes small, angular, yellow-to-brown spots that are surrounded by yellow halos (Figure 7). The angular spots enlarge and coalesce to produce large, irregular dead areas. The centers of these dead areas tear away, and infected leaves have a tattered appearance (Figure 8). Bacterial blight typically occurs in the mid to upper canopy. It is common after heavy rains, especially if temperatures remain cooler than normal.

How to distinguish bacterial blight from SVNV: Bacterial blight lesions have yellow halos and are smaller than those caused by SVNV. Leaves affected by bacterial blight appear tattered, unlike those affected by SVNV.

Bacterial Pustule (Xanthomonas campestris pv. glycinea)

Bacterial pustule causes small, yellow-green spots with angular, reddish brown centers (Figure 9). Small raised bumps (pustules) often develop on the undersides of infected leaves (Figure 10) and are typically found in the upper canopy. The disease is favored by high temperatures and above average rainfall.

How to distinguish bacterial pustule from SVNV: Bacterial pustule is the only common soybean disease in the Midwest that produces pustules on the leaf surface.

Cercospora Leaf Blight (Cercospora spp.)

Young SVNV lesions that have not developed distinct margins can be easily confused with Cercospora leaf blight. Cercospora leaf blight starts as mottled purple-to-orange discoloration that progresses to a characteristic orange or bronze appearance (Figure 11). Affected leaves often develop a leathery texture. This disease is most common in the mid- to late season.

How to distinguish Cercospora leaf blight from SVNV: Cercospora leaf blight symptoms occur only on the upper leaf surface.

Downy Mildew (Peronospora manshurica)

Downy mildew causes light green to yellow, irregular-shaped spots on the upper surfaces of the top leaves (Figure 12). On the undersides of affected leaves, the organism may grow out of the center of these spots, producing visible fuzzy growth (Figure 13).

How to distinguish downy mildew from SVNV: Downy mildew lesions may exhibit fuzzy growth on the undersides of leaves. Unlike SVNV lesions, downy mildew lesions are not typically associated with leaf veins.

Phyllosticta Leaf Spot (Phyllosticta sojaecola)

Phyllosticta leaf spot is a minor soybean disease that produces circular, irregular- or V-shaped lesions that are gray or tan and have narrow, dark margins (Figure 14). As lesions age, numerous small, black specks may be visible within them.

How to distinguish Phyllosticta leaf spot from SVNV: The dark, black fungal structures found in Phyllosticta leaf spot lesions are not found in SVNV lesions.

Sudden Death Syndrome (Fusarium virguliforme)

Sudden death syndrome (SDS) causes yellowing or death of leaf tissue between the veins, while veins remain green (Figure 15). Early interveinal yellowing can sometimes be confused with SVNV (Figure 16). As the disease progresses, infected leaflets may curl, shrivel, and eventually drop off, leaving only the petiole attached.

How to distinguish SDS from SVNV: SDS Symptoms occur between the veins rather than on or along the veins as with SVNV.

Herbicide Damage

SVNV can also be confused with herbicide damage from ALS inhibitor and ACCase inhibitor herbicides.

ALS Inhibitors

ALS inhibitor herbicides are widely used for preemergence and postemergence control for a broad range of weed species in soybean. There are many different herbicide products with this mode of action. ALS inhibitor injury includes stunting, leaf yellowing, inhibition of terminal growth, red veins on the undersides of leaves, and shortened internodes (Figure 17). Damage from ALS inhibitors develops slowly, appearing first on new growth.

How to distinguish ALS inhibitor injury from SVNV: ALS inhibitor injury symptoms typically appear earlier in the season than SVNV symptoms. Symptoms of ALS injury will also be more uniform among affected plants where phytotoxic concentrations have been applied in comparison to the random distribution of SVNV lesions. Review your herbicide program to determine if carryover from the previous season could occur.

ACCase Inhibitors

Quizalofop (Assure II, Targa) is a postemergence ACCase inhibitor grass herbicide that is commonly used to control volunteer corn and grassy weeds in soybean. Quizalofop can cause damage along the leaf vein that is similar to SVNV symptoms (Figure 18).

How to distinguish ACCase inhibitor injury from SVNV: Because quizalofop injury is so similar to the symptoms caused by SVNV, it is very important to review the field’s weed management program to rule out herbicide injury. Send leaf samples to a diagnostic laboratory for proper SVNV identification. Furthermore, more uniform symptoms of ACCase damage are anticipated shortly after herbicide application.

Vectors and SVNV

Orthotospoviruses are transmitted by a group of insects called thrips. To date, as many as 15 thrips species are known to be vectors of orthotospoviruses, but only three species are confirmed vectors of SVNV. Soybean thrips (N. variabilis) is the most important vector of SVNV, while tobacco thrips (Frankliniella fusca) and eastern flower thrips (F. tritici) may have a minor role in SVNV field transmission. Additional investigation may reveal other thrips species commonly associated with soybean production in the United States and Canada that may also have a role in SVNV spread.

Adult thrips are barely visible to the unaided eye (Figure 19). The insect feeds with a rasping-sucking mouthpart that leaves small, dash-like scars on leaves. Thrips development depends on temperature, and adult females can survive for three to five weeks.

When nymphs emerge from eggs (Figure 20), they can acquire SVNV by feeding on an infected source plant. After pupation, infected adults spread the virus to additional plants. If the virus is acquired by adult thrips, transmission to additional plants is not possible, as the virus can only complete its lifecycle when acquired by immature stages of thrips (nymphs). As a result, thrips species that reproduce on soybeans are considered the most relevant, and only these species would be the target for management.

Eggs from an infected adult do not carry the virus, but the virus may be capable of overwintering in living weed hosts and within adult thrips migrating from more southern latitudes in the spring and early summer.

Laboratory Detection

Confirming virus infection is difficult since virus diseases often resemble other foliar diseases or disorders, such as herbicide injury or nutrient imbalances. The only way to positively confirm a diagnosis of SVNV (or any virus) is through laboratory testing. The virus is easier to detect in leaf samples with early disease symptoms. Once lesions have turned from yellow to brown, it is difficult to detect the virus in symptomatic tissue. Contact your state’s land-grant university or private diagnostic laboratory for pricing and sampling procedures.

Yield Loss, Economic Impact, Management

SVNV has not been documented to cause yield losses. It has been implicated in minor changes in seed quality, such as reducing oil concentration. SVNV is generally considered a cosmetic problem. We currently do not suggest insecticide applications in response to SVNV detection because vector control has not typically reduced virus incidence for thrips-transmitted diseases. Farmers should use certified disease-free seed to limit the chance of seed transmission. Farmers should also be aware that increased SVNV symptom severity has been observed in late-planted soybeans.

Researchers will continue to monitor SVNV and assess its potential impact to determine the best management options. Future recommendations will be developed as we learn more about this disease.

Acknowledgements

Authors

Damon Smith, University of Wisconsin-Madison; Chris Bloomingdale, Michigan State University; Nolan Anderson, Texas A&M University; Carl Bradley, University of Kentucky; Martin Chilvers, Michigan State University; Russ Groves, University of Wisconsin-Madison; Daren Mueller, Iowa State University; Alejandro Olmedo-Velarde, Iowa State University; Edward Sikora, Auburn University; Albert Tenuta, Ontario Ministry of Agriculture, Food and Agribusiness; and Kiersten Wise, University of Kentucky.

Reviewers

Tom Allen, Mississippi State University; Alyssa Betts, University of Delaware; Mandy Bish, University of Missouri; Maira Duffeck, Oklahoma State University; Travis Faske, University of Arkansas; Horacio Lopez-Nicora, The Ohio State University; Trey Price, LSU AgCenter; Madalyn Shires, South Dakota State University; Darcy Telenko, Purdue University; Richard Wade Webster, North Dakota State University

Sponsors

The Soybean Disease Management series is a multi-state collaboration sponsored by the North Central Soybean Research Program (NCSRP) through the Soy Checkoff. The authors thank the United States Department of Agriculture - National Institute of Food and Agriculture, the Grain Farmers of Ontario, and United Soybean Board for their support. Contributors to this series come from land-grant universities in the North Central states and Canada.

How to cite: Smith, D., Bloomingdale, C., Anderson, N., Bradley, C., Chilvers, M., Groves, R., Mueller, D., Olmedo-Velarde, A., Sikora, E., Tenuta, A., Wise, K. 2026. An Overview of Soybean Vein Necrosis Virus. Crop Protection Network. CPN-1003. doi.org/10.31274/cpn-20190620-025.