Destructive diseases of soybean – sudden death syndrome and white mold – observed in the state

Signs and symptoms of a few soybean diseases have begun to show up in the last few weeks in some areas of the state.  Two of these diseases, sudden death syndrome (SDS) and Sclerotinia stem rot (a.k.a. white mold) certainly are going to cause economic losses in some growers’ fields this year.

Symptoms of SDS that currently are being observed are interveinal chlorosis and necrosis of the leaves (veins remain green while the tissues between the veins turn yellow and then brown).  These symptoms look exactly like the foliar symptoms caused by a different disease, brown stem rot.  Brown stem rot, however, will cause internal browning of the pith in soybean stems, while SDS does not affect soybean stems.  On SDS-affected plants, the leaves will fall off eventually, while the petioles will remain attached to the stems and branches.  In some cases, a bluish-white mass of spores of the SDS fungus (Fusarium virguliforme) may be observed on the roots.  Although the foliar symptoms of SDS are now being observed, infection by the SDS fungus occurred during the seedling stage, not long after planting.  The symptoms that are now being observed are the effect of toxins that the SDS pathogen produces that are phytotoxic.  Cool and wet weather after planting and the recent rainfall received in parts of the state were favorable for infection and disease development, and are the reasons why SDS incidence is high in some areas this year.  The primary method of managing SDS is to choose the most resistant soybean varieties available.  Some evidence has shown that high soybean cyst nematode (SCN) egg populations may also increase the likelihood of severe SDS; therefore, managing SCN populations through resistant varieties and crop rotation may also reduce the risk of SDS.  Unfortunately, there currently are no fungicide products registered that are effective in managing SDS, but an experimental fungicide seed treatment known as “ILeVO” that is currently making its way through the EPA registration process has shown efficacy against SDS in University of Illinois field trials.

Symptoms of sudden death syndrome of soybean (Photo by C. Bradley).

 

A bluish-white mass of spores of the SDS fungus (Fusarium virguliforme) on a soybean root (Photo by C. Bradley).

 

White mold can be observed in fields located in the northern half of Illinois this year.  The appearance of this disease also is weather-related.  Areas in the northern half of the state, that were cooler and wetter than normal after soybean plants began to flower, are the areas that are affected the most severely.  Unfortunately, once white mold signs and symptoms are detected in the field, fungicide applications generally will be futile, as the damage has already been done.  Management of white mold was discussed in an earlier article of the Bulletin this year (http://bulletin.ipm.illinois.edu/?p=2412).  Growers with severe levels of white mold may encounter some discounts at the elevator this year for high levels of foreign matter.  Some sclerotia (dark survival structures produced by the white mold fungus – Sclerotinia sclerotiorum) that are formed on plants may similar in size to the seed, and will make their way to the hopper and eventually the elevator, where discounts may be received.

 

Soybean plants dying prematurely because of white mold in a field in Champaign County (Photo by K. Ames).

 

White mycelia of the white mold fungus (Sclerotinia sclerotiorum) on a soybean plant (Photo by C. Bradley).


2014 Ewing Demonstration Center Fall Field Day

2014 Ewing Demonstration Center Fall Field Day

The University of Illinois Extension will host its annual Ewing Demonstration Center Fall Field Day on Thursday, September 11, 2014 at 9 a.m.  The Ewing Demonstration Center at is located at 16132 N. Ewing Rd; Ewing IL 62836, on the north edge of the village of Ewing, north of the Ewing Grade School on north Ewing Road.  Watch for signs.

The ongoing research plots this year consist of a soybean cover crops trial, LibertyLink soybean variety trial, insecticide/fungicide trial on soybeans, corn population study, drought tolerant corn hybrid evaluation, and new this year a pumpkin variety trial.

 

The topics to be discussed at Field Day include:

Fusarium Head Blight (Scab) and Vomitoxin Management in Wheat

  • Carl Bradley, Extension Specialist, Plant Pathology, University of Illinois Extension

Sky High Crop Scouting; Unmanned Aerial Drones

  • Dennis Bowman, Extension Educator, University of Illinois Extension

Alternative Forages and Harvesting Methods

  • Teresa Steckler, Extension Educator, Commercial Ag, University of Illinois Extension

Palmer Amaranth: Coming (Soon) to a Field Near You

  • Robert Bellm, Extension Educator, Commercial Ag, University of Illinois Extension

Cover Crops and Weed Management

  • Nathan Johanning, Extension Educator, Small Farms Local Foods, University of Illinois Extension

Refreshments will be provided by Franklin County Farm Bureau.

The field day is free and open to anyone interested.  A light lunch will be provided and registration is recommended by September 8, 2014 for an accurate meal count.

For additional information or to register, contact Marc Lamczyk at University of Illinois Extension Office in Franklin County at 618-439-3178 or lamczyk@illinois.edu.

 


2014 Field Day August 7 at Dixon Springs Ag Center

The 2014 Dixon Springs Agronomy and Horticulture Field Day presented by the University of Illinois, Department of Crop Sciences will be held on Thursday, August 7 at the Dixon Springs Ag Center.  The research center is located on IL Route 145, near Glendale, IL, 25 miles south of Harrisburg and 25 miles north of Paducah, KY.

Tours will start at 9:00 AM with the final bus leaving at 9:30. A lunch to follow will be provided by sponsors and UI Extension.

The following presenters will speak about current conditions and management challenges in field crop and horticulture production.

  • Carl Bradley: Fungicide Resistance
  • Angie Peltier: Corn Nematodes, The Hidden Menace in Your Fields
  • Jake Vossenkemper: Nitrogen on Soybeans
  • Rachel Cook: Tillage is Recreational, Fertilizer is Essential: A 44 Year Study
  • Jeff Kindhart: High Tunnels, Hydroponics and Mushrooms

For more information contact John Pike at 618-695-2441 or by email at jpike@illinois.edu


Brownstown Agronomy Research Center Field Day – August 6

The 2014 Brownstown Agronomy Research Center Field Day, presented by the University Of Illinois Department Of Crop Sciences, will be held on Wednesday, August 6. Extension researchers and specialists will address issues pertinent to the current growing season. The tour will start at 8 a.m. and will last about two and a half hours. It will be followed by lunch provided by U of I Extension.

Shaded tour wagons will take participants to each stop. These topics will be addressed:

  • N Fertilizer for Soybean:  Where’s the Yield? – Jake Vossenkemper, U of I
  • Tillage is Recreational, Fertilizer is Essential – Dr. Rachel Cook, SIU
  • Field Crop Diseases & Fungicide Treatments – Dr. Carl Bradley, U of I
  • Corn Nematodes:  the Hidden Menace in Your Fields – Dr. Angie Peltier, U of I
  • Factors Contributing to a Healthy Soil – Troy Fehrenbacher, NRCS

The 208-acre Brownstown Agronomy Research Center has been conducting crop research on the claypan soils of southern Illinois since 1937. More than 30 research and demonstration projects are conducted at the Center every year. Visitors are always welcome.

The research center is located south of Brownstown on IL Route 185, approximately 4 miles east of the IL Route 40 / 185 junction.

For more information, contact Robert Bellm (618-427-3349); rcbellm@illinois.edu
Visit us on the web at http://web.extension.illinois.edu/barc/


Assessing the risk of white mold (Sclerotinia stem rot) of soybean in 2014

White mold of soybean (a.k.a. Sclerotinia stem rot), caused by the fungus Sclerotinia sclerotiorum, is a disease that can occur in the northern half of the state in cool, wet years.  The most recent, widespread white mold epidemic in Illinois occurred during the 2009 season, where several fields in the northern half of the state were affected.  In some of the northern-most areas of Illinois, white mold can be considered a more consistent problem.

The white mold fungus overwinters in the soil as, small, black, and dense structures known as sclerotia.  These sclerotia germinate and form mushroom-like structures known as apothecia when soil remains moist for several consecutive days and soil temperatures are at 60 degrees F or below.  These apothecia generally will not form until the soil is shaded from sunlight due to soybean canopy closure.  Spores of the white mold fungus are shot out of the apothecia and land on senescing flower petals, where infections first occur on the soybean plants.  The white mold fungus becomes inactive when temperatures within the soybean canopy are above approximately 82 degrees, so infection and disease development may cease or slow down during periods of hot (above 82 degrees) and dry weather.

Apothecia of the white mold fungus germinating from a sclerotium. Image courtesy J. Venette, North Dakota State University.

 

Soybean plant with symptoms and signs of white mold (a.k.a. Sclerotinia stem rot). Image by C. Bradley.

 

So, what does the risk of white mold look like for 2014?  This is not an easy question to answer.  In general, rainfall has been consistent in the northern portion of the state, which would favor white mold, but recent temperatures in the 80s and 90s have not been favorable.  However, the short-term weather forecast shows cooler temperatures (60s and 70s).  If a cool and wet trend continues throughout soybean flowering, then the risk of white mold will be elevated.

In University of Illinois research trials, some fungicide products have shown efficacy against white mold.  Foliar fungicides will not provide complete control of the disease, but may reduce disease.  The results of University of Illinois trials conducted in 2009, 2010, and 2013 are shown in Tables 1-3.  Note that some of the more popular, frequently marketed fungicides are not listed in the tables since many do not have white mold on their label because of no to poor efficacy.  In these trials, the primary targeted growth stage to apply foliar fungicides was at R1 (beginning flower).  In some cases, R1 may occur before canopy closure.  If this is the case, then an application at canopy closure (rather than R1) might be more effective in protecting against white mold.  Also note that some treatments in these research trials were applied twice during the season.

 

Table 1. Results of soybean foliar fungicide research trials focused on white mold conducted in 2009 at the University of Illinois Northern Agronomy Research Center (DeKalb County).

Treatment Rate/A Incidence (%) 

8-11-09

Incidence (%) 

9-14-09

Yield (bu/A)
Untreated check 75 95 24
Topsin 4.5 L 20 fl oz 43 96 24
Proline 3 fl oz 38 95 24
Domark 5 fl oz 68 98 23
Cobra herbicide 12.5 fl oz 15 51 42
Omega 1 pt 23 80 34
Endura (2x)* 8 oz 38 86 39
Aproach (2x)* 8 fl oz 35 80 40
LSD 0.05** 33 15 8

*All treatments were applied at the R1 growth stage (July 20, 2009).  Treatments followed by “(2x)” were applied again 9 days later.

**Least significant difference (alpha level = 0.05).  Treatment values that differ by this number can be considered significantly differ from one another.

 

Table 2. Results of soybean foliar fungicide research trials focused on white mold conducted in 2010 at the University of Illinois Northern Agronomy Research Center (DeKalb County).  Funded in part by the Illinois Soybean Association.

Treatment Rate/A Incidence (%) 

8-11-09

Incidence (%) 

9-14-09

Yield (bu/A)
Untreated check 18 95 62
Topsin 4.5 L 20 fl oz 9 83 61
Proline 3 fl oz 10 89 66
Domark 5 fl oz 7 76 63
Cobra herbicide 6 fl oz 6 86 56
Omega 1 pt 2 70 58
Endura 8 oz 4 79 69
Aproach (2x)* 8 fl oz 11 79 66
LSD 0.05** 11 NS 8

*All treatments were applied at the R1 growth stage (July 10, 2010).  Treatments followed by “(2x)” were applied again 7 days later.

**Least significant difference (alpha level = 0.05).  Treatment values that differ by this number can be considered significantly differ from one another.  “NS” indicates that no treatments were significantly different from each other.

 

Table 3. Results of soybean foliar fungicide research trials focused on white mold conducted in 2013 at the University of Illinois Northern Agronomy Research Center (DeKalb County). Treatments were applied at the R1 growth stage unless indicated otherwise.

Treatment Rate/A Incidence (%) 

9-19-13

Yield (bu/A)
Untreated check 33 53
Incognito 4.5F 20 fl oz 20 68
Incognito 4.5F + Orius 3.6F* 20 fl oz + 4 fl oz 0 62
Proline + Stratego YLD** 3 fl oz + 4.65 fl oz 3 58
Domark 5 fl oz 3 62
Cobra herbicide 6 fl oz 25 52
Endura 8 oz 3 64
Aproach 8 fl oz 13 61
Fortix 5 fl oz 15 56
LSD 0.05*** 22 7

*Incognito was applied alone at the R1 growth stage and was followed by Orius applied alone at R3.

**Proline was applied alone at the R1 growth stage, and was followed by Stratego YLD applied alone at R3.

***Least significant difference (alpha level = 0.05).  Treatment values that differ by this number can be considered significantly differ from one another.  “NS” indicates that no treatments were significantly different from each other.

Overall, the highest level of white mold control will be achieved when several management practices are integrated (i.e. choosing the most-resistant varieties, utilizing recommended seeding rates, applying a foliar fungicide, and applying a biocontrol product).  For more information about white mold and management of this disease, go to http://www.soybeanresearchinfo.com/pdf_docs/WhiteMold_NCSRP.pdf, where a 7-page publication on white mold (developed in 2011) can be downloaded.


Wheat scab rearing its ugly “head” again in 2014

Head scab of wheat (a.k.a. Fusarium head blight) is showing up in the southern portion of Illinois.  In many cases, incidence is moderate to high (over 50% of the heads affected).  Affected wheat heads will appear “bleached” in color.  Heads often are partially affected, with both healthy green and affected bleached areas being present in the same head.  Although I have not been in all wheat production areas in the state, my general observations are that fields in southern Illinois (south of Interstate 70) range from a moderate to high incidence of scab.  The differences in scab incidence from field to field likely are due to differences in susceptibility of the varieties planted, application or no application of fungicides, and local weather.

Wheat field affected by head scab (Fusarium head blight). Note the "bleached" heads. (Photo by Carl Bradley)

Wheat growers may want to evaluate the level of scab in their fields.  It is easiest to observe this disease before heads completely mature.  Growers with moderate to high levels of scab should consider making adjustments to their combine that would allow low test-weight, scabby kernels to be blown out the back of the combine.  Recent research conducted at the Ohio State University indicated that adjusting the combine’s fan speed between 1,375 and 1,475 rpms and shutter opening to 90 mm (3.5 inches) resulted in the lowest discounts that would have been received at the elevator due to low test weight, % damaged kernels, and level of the mycotoxin deoxynivalenol (DON; vomitoxin) present in the harvested grain (Salgado et al., 2011).

 

Wheat head affected by scab (Fusarium head blight). (Photo by Carl Bradley)

Reference:

Salgado, J. D., Wallhead, M., Madden, L. V., and Paul, P. A. 2011. Grain harvesting strategies to minimize grain quality losses due to Fusarium head blight in wheat. Plant Disease 95:1448-1457.


Considerations for fungicide management of Fusarium head blight of wheat

Wheat plants are now beginning to head out and flower in parts of southern Illinois. During this critical time of wheat development, wheat becomes susceptible to infection by Fusarium graminearum, the causal agent of Fusarium head blight (FHB; also known as scab) (Fig. 1). This disease can cause reduced grain yield, test weight, and quality. In addition, the fungus can produce toxins that will contaminate grain such as deoxynivalenol (DON; also known as vomitoxin). Harvested grain with high levels of DON may be discounted or outright rejected at the elevator. To achieve the best management of FHB, different management practices must be implemented, such as planting wheat into fields that were previously cropped to soybean (rather than corn), planting wheat varieties with moderate to high levels of resistance to FHB, and applying foliar fungicides at the proper timing. Of these different management practices, the application of foliar fungicides is the only one that can be done during the growing season and is the main focus of this article.

Fig. 1. Symptoms of Fusarium head blight (scab) of wheat (note the “bleached” heads).

Multiple fungicides are registered for use on wheat, but only a few have efficacy in managing FHB. Fungicides available for FHB management all belong to the triazole class of fungicides and are Caramba (BASF Corporation), Prosaro (Bayer CropScience), Proline (Bayer CropScience), and products that contain tebuconazole as their solo active ingredient. Of these products, the best efficacy has been obtained with Prosaro and Caramba in multi-state university field research trials. Proper fungicide application timing is critical in achieving the best efficacy. The best application timing is considered to be when plants are beginning to flower (early anthesis – Feekes growth stage 10.5.1), but some efficacy may still be achieved slightly before or after Feekes 10.5.1 (Table 1). In regards to fungicide application timing, it is important to always follow the label recommendations and consider the preharvest interval (PHI) requirements (PHI for Caramba, Prosaro, Proline, and tebuconazole products is 30 days). Fungicide products that contain strobilurin active ingredients should not be applied for control of FHB, and most do not list FHB control or suppression on their label. In multiple university research trials, strobilurin fungicides have been shown to increase DON levels in grain compared to non-treated checks. Therefore, it is extremely important that only effective triazole fungicides be applied for management of FHB.

Table 1. Effect of fungicide application timing on Fusarium head blight (FHB) control in wheat. Results represent data collected from Dixon Springs, IL in 2009, and Brownstown, IL, Carbondale, IL, Dixon Springs, IL, and Urbana, IL in 2010.

Fungicide

Application timing

FHB (% control)*

Prosaro @ 6.5 fl oz

Feekes 10.5

35 b

Feekes 10.5.1

59 a

5 days after Feekes 10.5.1

37 b

Caramba @ 13.5 fl oz

Feekes 10.5

38 b

Feekes 10.5.1

61 a

5 days after Feekes 10.5.1

36 b

*Values followed by the same letter in the table are not significantly different with 95% confidence.

When making a decision on if a fungicide application is needed, FHB risk should be assessed. A FHB Prediction Tool is available on-line at www.wheatscab.psu.edu. This risk is based on weather conducive for FHB, and should be assessed for each field as they begin to develop heads in anticipation of flowering. On May 9, 2014, a LOW risk of FHB was present in all of Illinois; however, this status can and will change depending on weather conditions. Therefore it is important to continually monitoring the FHB Risk Prediction Tool as more and more wheat fields get closer to the flowering stage.


Ready for Samples at the University of Illinois Plant Clinic

Welcome to another Diagnostics season! Samples have been steadily appearing this spring here at the Clinic in our 39th year of operation. On the field front, there have been concerns with virus disease diagnosis in wheat. On the home landscape front, there is a mountain of winter kill and windburn injury from the harsh winter just past.

The University of Illinois Plant Clinic began year-round operation in the fall of 2011. Our new location is in Jonathan Baldwin Turner Hall on the south end of the Urbana campus. During the winter, our hours are irregular due to trainings and winter meetings so call ahead. However, we resume regular business hours, 8am-12pm and 1pm-4:30pm, on Monday April 28th, 2014.

Example of a great sample: Sample form, symptomatic plant, protected root ball and payment

Plant Clinic services include plant and insect identification, diagnosis of disease, insect, weed and chemical injury observation (chemical injury on field crops only), nematode assays, and help with nutrient related problems, as well as management recommendations involving these diagnoses. Microscopic examinations, laboratory culturing, virus assays, and nematode assays are some of the techniques used in the clinic. Many samples can be diagnosed within a day or two. Should culturing be necessary, isolates may not be ready to make a final reading for as much as two weeks. Nematode processing also requires about 1-2 weeks depending on the procedure. We send your final diagnoses and invoices to you through both the US mail and email. If you provide your email address on the sample form you will get your information earlier.

Please refer to the Plant Clinic website for additional details on sampling, sample forms, fees and services offered. If you have questions about what, where, or how to sample call us at 217-333-0519. Whenever submitting a sample, provide as much information as possible on the pattern of injury in the planting, the pattern on individual affected plants, and details describing how symptoms have changed over time to cause you concern.

Our fees vary depending on the procedure necessary. General diagnosis including culturing is $15, ELISA and immunostrip testing is $25, Nematode analysis for SCN or PWN is $20, Specialty Nematode testing (such as corn) is $40.

Please include payment with the sample for diagnosis to be initiated. Checks should be made payable to the University of Illinois or to the Plant Clinic. Companies can setup an account, call and we will accommodate you. Call if uncertain of which test is needed.

Plant Clinic location, S-417 Turner Hall, 1102 S. Goodwin, Urbana IL 61801

Drop off a sample:

You can also drop off a sample at S-417 Turner Hall. Park in the metered lot F 28 on the east side of Turner or at the ACES library metered lot on the west side of Turner. Come in the South door. Take the elevator located in the SE corner of the building. Turn left when exiting the elevator; we are located along the SE corridor of the 4th floor. Please use the green drop box located just outside S-417 if we are temporarily out of the office.

Sending a sample thru US mail or delivery service address to:

University of Illinois Plant Clinic
1102 S. Goodwin, S-417 Turner Hall
Urbana, IL 61801

Social Media: We have a lot of ways to keep you up to date on what is happening at the Plant Clinic and about other plant and pest issues. Follow the U of I Plant Clinic on Facebook, YouTube or, Blogger.


2014 Illinois Crop Management Conferences Registration Now Open

The latest research information on crop production and management issues will be discussed at four University of Illinois Crop Management Conferences this winter. These two-day conferences are designed to address a wide array of topics pertinent to crop production, pest management, and natural resource issues and provide a forum for discussion and interaction between participants and university researchers.

Certified Crop Advisers can earn up to 13 hours of CEU credit. Advance registration, no later than one week before each conference, is $130 per person. Late and on-site registration is $150. Dates and location for the four regional conferences are listed below. Links to the complete agendas and registration information for each conference are located on the Crop Sciences Research and Education Center web page here.

 

January 22-23: Mt. Vernon – Krieger/Holiday Inn Convention Center. For more information, contact Robert Bellm, (618-427-3349); rcbellm@illinois.edu . Register online at http://extension.illinois.edu/go/icmcmtvernon

January 29-30: Springfield – Northfield Inn Conference Center. For more information, contact Robert Bellm, (618-427-3349); rcbellm@illinois.edu . Register online at http://extension.illinois.edu/go/icmcspringfield

February 6:  Champaign – i-Hotel and Conference Center. For more information, contact Dennis Bowman, 217-244-0851); ndbowman@illinois.edu . Register online at http://extension.illinois.edu/go/icmcchampaign

February 12-13: Malta – Kishwaukee College Conference Center. For more information, contact Russ Higgins (815-274-1343); rahiggin@illinois.edu . Register online at http://extension.illinois.edu/go/icmcmalta


Soybean rust: status and risk

Observations of soybean rust in southern states indicate that the pathogen (Phakopsora pachyrhizi) is beginning to move northward towards Illinois. Based on current movement, soybean rust likely will arrive in Illinois again this year, but it may not be in the state early enough to cause any yield losses. Late-planted fields would be the most at risk to losses caused by soybean rust. In general, once soybean plants reach the R6 stage (full seed stage), yield loss is unlikely to occur with any infections by the soybean rust pathogen. Many soybean fields in the state are now at the R5 stage (beginning seed stage). If spores of the soybean rust pathogen arrive in Illinois, favorable conditions must occur for infection and disease development to occur. Conditions that are favorable for soybean rust include moderate temperatures, frequent rainfall, and cloudy skies.

Soybean rust observations in North America can be viewed at the IPM PIPE website (http://sbr.ipmpipe.org). Although soybean rust sentinel plots are no longer maintained in Illinois (due to lack of funding), monitoring for soybean rust in Illinois is still occurring in targeted risk areas in the state. Any soybean leaves that are suspicious for soybean rust should be sent to the University of Illinois Plant Clinic (http://web.extension.illinois.edu/plantclinic/).

Other diseases that can be confused with soybean rust, such as bacterial pustule and Septoria brown spot, have been observed in Illinois this year. Of these two diseases, bacterial pustule may be the most easily confused with rust. One major difference between symptoms caused by bacterial pustule and soybean rust is that the pustules on the leaves will occur on both the upper- and underside of the leaf with bacterial pustule, but only on the underside of the leaf with soybean rust. Continue to monitor the IPM PIPE website and the Bulletin for additional updates on soybean rust.

Symptoms of soybean rust on soybean leaflets (photo courtesy D. Mueller, Iowa State University).

 

Soybean rust pustules filled with spores on the underside of a soybean leaflet (magnified) (photo courtesy D. Pedersen, Univ. IL).

 

 

Symptoms of bacterial pustule on a soybean leaflet (photo courtesy D. Pedersen, Univ. IL).

 

 

Bacterial pustules that can be found on either the upper- or undersides of soybean leaflets (magnified) (photo courtesy D. Pedersen, Univ. IL).

 

Symptoms of Septoria brown spot on a soybean leaflet (photo by C. Bradley).