A new soybean disease enters Wisconsin: Soybean Vein Necrosis Disease (SVND)

Soybean Vein Necrosis Disease

Soybean Vein Necrosis Disease (source: http://agdev.anr.udel.edu/weeklycropupdate/?p=3762)

Soybean diseases are always hard to diagnose. I use the color picture guides as a reference but if I cannot positively identify them I usually send down a sample to the UW Plant Disease Diagnostic clinic for a positive identification. Remember a virus, like the soybean vein necrosis virus, cannot be controlled with a fungicide. The best way to prevent a soybean virus is to keep the thrips away from your crop. Thrips infect the soybean plants when they feed upon them, similar to how mosquitoes transmit the west Nile virus. No matter what disease you suspect you may encounter out in your soybean fields, the best defense is a having a strong, well-fed plant with as few stressors acting upon it as possible.

I found the following article by Damon Smith (Extension Field Crops Pathologist, Department of Plant Pathology, University of Wisconsin-Madison) in the recent edition of the Wisconsin Crop Manager to be very insightful.

In 2012 soybean vein necrosis disease (SVND) was described for the first time in Wisconsin. This is a relatively new disease of soybean, which is caused by Soybean vein necrosis virus (SVNV). SVNV was first described in 2008 in the Mid-south soybean production region. Since then, SVND has been found in much of the major soybean production region of the U.S. including the North Central region.

SVNV is a Tospovirus similar to Tomato spotted wilt virus. It is the first Tospovirus known to infect soybean. Tospoviruses are known to be very destructive on other plant crops, therefore, there is a lot of interest in determining the importance of SVNV in soybean production systems. Very little is actually understood about the epidemiology and also the management of SVND. Researchers around the country are working on various aspects of the system and several state and regional soybean commodity boards have funded research on SVND.

Recently Zhou and Tzanetakis (2013) described some of the first studies on the epidemiology of SVNV. Their findings suggest that SVNV is like other Tospoviruses in that it is primarily transmitted by thrips vectors. Soybean thrips are a commonly occurring insect in the Mid-south and were used in their studies to demonstrate that the virus can be transmitted via thrips vectors. In Wisconsin, soybean thrips are not as common. However, other species of thrips can be found in soybean fields depending on the time of the season. Through funding granted by the Wisconsin Soybean Marketing board, our laboratory is currently monitoring thrips populations in soybean fields around the state. We are evaluating thrips species and populations over time through trapping methods. We are also surveying these fields for SVND severity and documenting any variety resistance in soybean cultivars commonly grown in Wisconsin. Finally, we have separate trials were we are evaluating yield loss due to SVNV. Our research will complement research in other states and the results will be used to develop and disseminate management recommendations for SVND in the North Central Region over the next several years.

(Source: http://ipcm.wisc.edu/blog/2013/09/soybean-vein-necrosis-disease-in-wisconsin-with-video/)

– Rob Shields, Agronomist

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WARNING: WHITE MOLD FOUND in soybean fields!

We have found areas of white mold starting aggressively in area soybean fields. It is too late to use the herbicide Cobra®, but you could us a fungicide such as Domark®, at 5 oz. per acre, to help slow down the progression of this devastating disease. It is also recommended to add in 6.4 oz. per acre of MasterLock® (a new premix of Interlock® and Preference®) to aid in the dispersal of the fungicide on the soybean plants. Below are some photos to assist you in determining if you have any white mold in your fields. (Click photos to enlarge them.) Please let us know if you need any help scouting your fields.

– Rob Shields, Agronomist

White mold 1 White mold 2 White mold 3

Disease pressure is high in soybeans this year…

Today we looked at a number of soybean fields that have been attacked by a number of soil born diseases. Because of the extreme conditions this season – cool and wet, then hot and dry – a lot of fields are starting to show problem areas. The field pictured below in particular looks like it has some areas of rhizoctonia starting. We are sending some samples down to the plant pathology lab to confirm our diagnosis.

– Rob Shields, Agronomist

Diseased area in soybean field.

Diseased area in soybean field.

Rhizoctonia in soybeans.

Rhizoctonia in soybeans.

Stressed, stunted, and uneven corn found throughout our trade area…

Yesterday, I looked at some fields near our Melrose and Galesville locations and saw patterns of stressed, stunted, and uneven corn. These patterns have been seen all across our trade area, especially in medium to fine textured soils. It appears these patterns have shown up in our fields for a number of reasons. The primary culprit is the weather conditions we have gone through. The pounding rains have helped to compact these soils and reduce or eliminate the amount of oxygen present in the profile. Combine this with cool, cloudy and wet conditions and you can see the results. Areas of the field that have tighter soils from either the type of soil present or traffic patterns show the stunted symptoms much easier. If you can cultivate, that would help break up these tight soils and allow some air movement to occur. If cultivation is not an option, please try to reduce the stress on the plant wherever possible by keeping the field weed free (use a residual herbicide whenever possible); maintaining adequate fertility (confirm with tissue analysis); reducing the possibility of diseases (consider a foliar fungicide); and monitoring nematode pressure. Please let us know if you diagnose any issues you are seeing in your fields.

Stunted corn near Galesville.

Stunted corn near Galesville.

Stunted corn near Melrose.

Stunted corn near Melrose.

Stunted corn near Melrose.

Stunted corn near Melrose.

– Rob Shields, Agronomist

Headline® Fungicide On Alfalfa

Average total stem counts for sites treated with Headline were 31% higher than untreated sites.

Average total stem counts for sites treated with Headline® were 31% higher than untreated sites.

With the cold, wet spring and summer we are having, it is the perfect time to spray Headline® fungicide on your alfalfa. Headline is a fast acting, broad spectrum fungicide that delivers a high level of activity on more than 50 major diseases that can threaten yield and crop quality. We have seen tremendous yield increases over the past couple years using Headline; we also see higher quality feed as well.

Untreated plants vs. plants treated with Headline® fungicide.

Untreated plants vs. plants treated with Headline® fungicide.

Not only does Headline provide excellent disease control, it actually promotes improved plant health.

The unique chemistry of Headline enables more efficient nutrient uptake, more robust plant growth, and better stress tolerance to heat, hail, wind, and drought. Ultimately, this means healthier plants and higher yield potential.

Growers who have used Headline on their alfalfa report far less disease, more vigorous plant growth, higher stress tolerance, better standability, and, of course, higher yield — helping reduce losses and improve ROI.

044To be more efficient you can also run Ascend, Micros, and your insecticide for leafhoppers, Alfalfa weevils, etc., at the same time, greatly improving the health and yield of your high dollar alfalfa field.

To learn more about the benefits of using Headline fungicide on your alfalfa fields, call any of the Agronomy locations of Allied Cooperative and talk to one of our agronomists soon.

Thank you,

Izaak Rathke, Sales Manager