Soybean diseases taking off in Iowa

decrease font size  Resize text   increase font size       Printer-friendly version of this article Printer-friendly version of this article

Several soybean diseases have popped up over the past several weeks across Iowa. Although some diseases are quite severe in certain fields, others are only scattered problems in parts of the state. Regardless, it is important to scout and identify what diseases are present and to keep track of where the diseased spots are occurring in the field. This can help with variety selection and possible management of these diseases in the future. Some of the more common diseases found in our field scouting over the past few weeks include:

click image to zoomFigure 1. Yellow patches of sudden death syndrome in a soybean field. Leaves of infected plants can fall off but petioles will stay attached to the plant. Sudden death syndrome (SDS)

Severity of SDS has increased in many parts of the state. While it is still mostly pockets within a field, it is the cause of many of the yellow spots observed in soybean fields (Figure 1). Remember to check your soybean cyst nematode (SCN) counts this fall in fields with SDS to see if SCN is contributing to the SDS problem. In July 2014, we discussed the increased risk of SDS in 2014 in this article.

Brown stem rot (BSR). This disease is still mostly only in northern Iowa but has also been reported in parts of eastern Iowa. Remember to split stems to distinguish between SDS and BSR. This article from earlier in the season explains more about how to tell SDS from BSR, as well as discusses BSR management issues.

Top dieback

While the cause of top dieback is unknown, many yellow spots in fields are the result this disease. Top dieback appears as yellowing on the outside margins of leaves in the upper canopy (much like potassium deficiency, but in the upper canopy). The cause of this disease is still up for debate, but potassium deficiency, SCN, and the Phomopsis/Diaporthe disease complex (fungi associated with stem canker and pod and stem blight) may be culprits. Several years ago, a very thorough article was written about top dieback.

click image to zoomFigure 2. Fluffy white growth on the leaf underside is a sign of downy mildew infection. Downy mildew

This foliar disease is becoming more common as the season goes on. Downy mildew can be identified by the light green, irregular shaped lesions on the top side of the leaf and fluffy white growth on the under side of the leaf (Figure 2).

Frogeye leaf spot

Another foliar disease that is showing up in parts of Iowa, especially in the southern counties, is frogeye leaf spot. Frogeye is fairly easy to identify by the gray lesions with purple borders.

click image to zoomCraig GrauFigure 3. Stem canker can be identified by examining stems for sunken, gray-brown lesions with reddish margins. Note green tissue below lesions. Stem canker

There have been a few isolated reports of stem canker, which is another disease that is more common after very wet springs. Look for distinct lesions on the stem to identify this disease (Figure 3).

White mold

There have been reports of white mold across most of Iowa; however, most cases have been fairly low incidence of the disease. Additional information on white can be found in this article.

click image to zoomFigure 4. Possible symptoms of soybean dwarf virus. Samples are being tested for confirmation that this virus is the cause. Other diseases seen in Iowa include Septoria brown spot and bacterial blight (both have been around for most of the growing season), soybean vein necrosis virus (SVNV) in southeast Iowa, and possibly soybean dwarf virus (Figure 4).

Many soybean diseases have similar symptoms to other diseases. If diagnosis is proving to be difficult, samples can be submitted to the Plant and Insect Diagnostic Clinic at Iowa State University. See this article for instructions on how to do so.


Prev 1 2 Next All



Buyers Guide

Doyle Equipment Manufacturing Co.
Doyle Equipment Manufacturing prides themselves as being “The King of the Rotary’s” with their Direct Drive Rotary Blend Systems. With numerous setup possibilities and sizes, ranging from a  more...
A.J. Sackett Sons & Company
Sackett Blend Towers feature the H.I.M, High Intensity Mixer, the next generation of blending and coating technology which supports Precision Fertilizer Blending®. Its unique design allows  more...
R&R Manufacturing Inc.
The R&R Minuteman Blend System is the original proven performer. Fast, precise blending with a compact foot print. Significantly lower horsepower requirement. Low inload height with large  more...
Junge Control Inc.
Junge Control Inc. creates state-of-the-art product blending and measuring solutions that allow you to totally maximize operating efficiency with amazing accuracy and repeatability, superior  more...
Yargus Manufacturing
The flagship blending system for the Layco product line is the fully automated Layco DW System™. The advanced technology of the Layco DW (Declining Weight) system results in a blending  more...
Yargus Manufacturing
The LAYCOTE™ Automated Coating System provides a new level of coating accuracy for a stand-alone coating system or for coating (impregnating) in an automated blending system. The unique  more...
John Deere
The DN345 Drawn Dry Spreader can carry more than 12 tons of fertilizer and 17.5 tons of lime. Designed to operate at field speeds up to 20 MPH with full loads and the G4 spreader uniformly  more...
Force Unlimited
The Pro-Force is a multi-purpose spreader with a wider apron and steeper sides. Our Pro-Force has the most aggressive 30” spinner on the market, and is capable of spreading higher rates of  more...
BBI Spreaders
MagnaSpread 2 & MagnaSpread 3 — With BBI’s patented multi-bin technology, these spreaders operate multiple hoppers guided by independent, variable-rate technology. These models are built on  more...


Comments (0) Leave a comment 

Name
e-Mail (required)
Location

Comment:

characters left


Grain Storage Systems

Behlen Grain Storage Systems offers large capacity bins with diameters from 16’ to 157’ and capacities exceeding 1,500,000 bushels. All ... Read More

View all Products in this segment

View All Buyers Guides

Feedback Form
Feedback Form