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

More cutworms found in area fields

We have found more CUTWORMS in the fields today. Please check your fields! Black and Dingy are eating our corn!

Black Cutworm at F-5 today.

Black Cutworm at F-5 today.

Dingy Cutworm found today.

Dingy Cutworm found today.

– Rob Shields, Agronomist

Dealing with wet fields, weeds, and pests this week (June 3-7)

This week is shaping up to be a wet one which is a problem for some of the fields that are weedy and too wet for us to get into to spray. Consider increasing rates, and heating up your tank mixes for better weed control on taller weeds when you do get into these fields later. Continue to be vigilant in looking for black cutworm clipping of corn.  The threshold is 3% of plants clipped to warrant a spray. In the potatoes, the first generation Colorado beetles are laying eggs so look for newly hatched larvae next week. Do stem and stand counts this week to determine populations, and weed scouting to see if the hilling operation missed any weeds. Watch out for common ragweed especially as they are very difficult to control if they get larger than 2 inches.

Colorado potato beetle

Colorado potato beetle

Common ragweed

Common ragweed

– Otto Oemig, Agronomist

Crane Damage and a Cutworm Alert!

We saw two big issues in fields today!

First, crane damage was seen just north of Adams today! Keep an eye on your field for crane damage! Look at the picture below – the cranes pulled the plants right out of the ground.

Crane damage seen just north of Adams, WI.

Crane damage seen just north of Adams, WI, on June 5, 2013.

Second, cutworms were found feeding just south of Adams this morning. Please check your fields or give us a call to help scout your fields ASAP, so that these pests don’t chew up your crop.

Cutworms spotted south of Adams, WI, on June 5, 2013.

Cutworms spotted south of Adams, WI, on June 5, 2013.

– Rob Shields, Agronomist

Reduce Stress on Your Crops Through Aggressive Scouting

With the challenging conditions this spring, it is more important than ever to scout your fields aggressively. It is critical that the insect, weed, disease, and nematode pressure be monitored accurately. When the crop is already stressed due to late planting and adverse weather conditions, it is important to reduce or eliminate additional stressors.

Alfalfa

On our alfalfa crop, we want to reduce the amount of disease pressure, especially during this wet season. One way to assist your alfalfa crop and reduce the presence of leaf disease is to apply a foliar fungicide. A foliar fungicide will allow the harvest to have more green leaves, from the soil surface to the top of the plant, than you would see without such treatment. This corresponds with increased yields and quality. I would also encourage you to look at tissue testing after you have adequate re-growth, to ensure that your alfalfa plants are finding the proper nutrients. It is important to watch the insect pressure in your alfalfa fields as well; the biggest insect pests we currently deal with are potato leaf hoppers and the alfalfa weevil. Weed pressure can also greatly impact the ability of an alfalfa field to produce. The most effective and least stressful option for weed removal on production alfalfa fields is to use the Roundup Ready® System. Other options, such as Raptor® herbicide, can set back the growth of the alfalfa. The Roundup Ready System also allows us to remove broadleaves easily from fields such as clover, dandelions, and thistle.

Corn

In our corn fields, we need be watching for insect pressure. Some common pests we deal with during spring and early summer are black cutworms, dingy cutworms, and armyworms. These pests are very destructive and can advance rapidly, increasing the need for regular aggressive scouting to help monitor these pest levels. When the corn hits the V5 stage (5 collars), you have the option to apply a foliar fungicide, such as Headline AMP® or Stratego® YLD. This practice may prove even more advantageous this season with all of the additional stressors that our corn crop is facing. Controlling the weeds in your corn fields is also critical. When conditions allow you to enter the corn fields this year, I would strongly encourage you to have at least 3 active ingredients in your spray mixture; I would not recommend Glyphosate alone to protect your crops. There are many different recipes you can use on your corn post-emergence. Selection of these recipes depends on many factors: weeds present, herbicides used to date, economics, and rotational restrictions (what are you going to be planting in this field down the road). An example of a post-emergence herbicide recipe on glyphosate tolerant corn could be 5# Glyphosate at 24 to 48oz (rate depends on weed height and species present) + Capreno® at 3oz/acre + Atrazine 4L at 1pt/acre (only if you are in an area that is legal to apply Atrazine) + the appropriate amount of surfactant and spray grade ammonium sulfate. There are many other post-emergence products that can be used in various combinations, such as Status® (safely-formulated dicamba), Cadet®, Laudis®, Halex™ GT, Prowl® H20, Lumax®, Hornet® WDG, and more.

Soybeans

On our soybean crop, it is very important to start clean and stay clean. As with corn, I would strongly encourage you to have a minimum of 3 active ingredients for your herbicide program. If your soybeans have not been planted yet, or have not emerged, there are a number of herbicides that can help burn down any weeds present and also offer some residual control, such as Authority® First, DUAL®, Gangster®, OpTill®, Valor®, and others. After the crop has emerged, our list of products changes somewhat. One of my favorites is to add Cadet® in at about .5 oz. per acre with Glyphosate. The Cadet will “flash” the soybeans, but it helps take down larger broadleaves such as Giant Ragweed and Lambsquarter, which Glyphosate alone would not. If there is any volunteer corn present, I would encourage you to add in a non-selective grass herbicide, such as Select®, Section® 2EC, Poast®, Fusion®, or Assure® II. When looking at other post-emergence herbicide products, it is important to consider crop safety, weeds present, height of weeds, and tank mix partners. Some products you might consider adding to your tank mix are Cobra®, Extreme® (mixture of Pursuit® and Glyphosate), Phoenix™, Raptor®, Resource®, and Warrant®. Disease control in soybeans starts with variety selection, followed by appropriate treatments of fungicide, insecticide, nematicide, and inoculants. After emergence, we can look into a foliar fungicide program to assist you with disease management programs. There are many products to choose from, and rates and timing are different for each product. It is best to discuss your product options with your agronomist to find the best fit for your crops. Some examples of these products include Stratego® YLD, Quadris®, Quilt®, Proline®, Priaxor®, Headline®, and Endura®. Insect control is also very important in soybeans. Last year we saw a lot of spider mite activity, and in past years we have seen outbreaks of soybean aphids. The best advice I can give on insect pressure in soybeans is to scout regularly and apply the appropriate insecticide when pest levels warrant an application.

Please contact one of our professional field scouts or agronomists to assist you with any field scouting you need done this season. I also highly encourage you to consider tissue testing, disease testing and nematode testing. This way we can more accurately recommend a course of action for you to manage your nutrient and pest levels.

– Rob Shields, Agronomist

Watch out for moths

Much of the corn across the area is emerging and some is already at V1 to V2. With the cool spring we have had we are seeing a lot of yellowing in the corn as it emerges. Due to the cold weather, insects have been slow to emerge and migrate in. Not many corn insects have been observed this week. We will be setting up our black light traps later this week to capture and monitor the levels of moths in the area. Key moths we watch out for are European corn borer, corn earworm, black cutworm, various armyworms, stalk borer, and hop vine borer. We monitor these moth counts to better focus our scouting operations on what pests are in the area at what times of the season. Watch out for frost damage later in the week as it is set to get almost to freezing on Thursday across much of our area. Many times the cold air can settle into low parts of the field and do damage.

– Otto Oemig, Agronomist