Symptoms of Sudden Death Syndrome Begin to Appear in Soybeans

Last week, symptoms of sudden death syndrome (SDS) began to appear in April 15-planted soybeans at the University of Illinois’ Northwestern Research Center in Warren County. Weather during the 2015 growing season has been favorable for the development of SDS: cool, moist soils after planting and frequent rains ever since. Symptoms began appearing approximately 3 weeks earlier than in 2014.

While the fungus that causes SDS (Fusarium virguliforme) infects roots of soybean seedlings very early in the growing season, foliar symptoms don’t typically appear until after soybean plants reach reproductive growth stages. Foliar symptoms begin with a yellowing of the tissue between leaf veins. This tissue then dies, becoming brown in color with only the leaf veins remaining green. Leaves eventually fall off, while petioles remain attached to the main stem. The earlier that symptoms develop and leaf drop occurs, the greater the potential for yield loss.

100_4431Foliar symptoms of sudden death syndrome (photo: A. Peltier).

While foliar symptoms of SDS can be easily confused with those of another disease – brown stem rot – one need only split the plant length-wise to distinguish the two. Brown stem rot causes browning of the inner-most stem tissue (pith) while stems of plants with SDS remain healthy. Blueish-white spores of Fusarium virguliforme can sometimes (not always) be seen on the roots of symptomatic plants.

fungal growthBluish-white spores of F. virguliforme (arrow) (photo: A. Peltier).

Although the most conspicuous symptoms of SDS occur in leaves, the fungus itself remains in the roots and in the stem nearest the soil line. Foliar symptoms are caused by toxins produced by the pathogen. These toxins are carried along with water to leaves through the xylem tissue. The SDS disease cycle has important implications as far as management is concerned: infection and colonization have long since taken place and there are no mid-season management tools with which to manage this disease. Management decisions must be made before the growing season begins.

The best way to manage SDS is to plant the most resistant varieties possible. Soybean varieties vary considerably in their level of genetic resistance. Seed companies typically provide SDS resistance ratings. To provide impartial SDS resistance ratings to help soybean producers more easily compare varietal resistance among seed brands, teams led by Drs. Jason Bond of Southern Illinois University and Silvia Cianzio of Iowa State University evaluated more than 500 soybean varieties (MGs 0 to V) from 19 different seed companies. Results from these 2014 check-off sponsored trials are posted here. Results from the 2015 trials are to be compiled and released in October in time for producers to use while making their 2016 seed purchases.

Research has also shown that SDS may be more severe in fields that also have high populations of the soybean cyst nematode (SCN). Monitoring SCN populations and planting SCN-resistant soybean varieties can also be important components to managing SDS.

The newest tools available for managing this disease are fungicidal seed treatments labeled specifically for SDS. While a University of Illinois Extension Plant Pathologist, Dr. Carl Bradley (now at the University of Kentucky) and his team conducted several SDS seed treatment trials. In these trials, the active ingredient in ILeVO (fluopyram) showed efficacy against SDS. Other SDS seed treatments are also currently being evaluated.

As the season progresses and we near harvest, check out the Northwestern Illinois Research Center’s Website and Blog for data from our 2015 SDS seed treatment trial and other research trials at this location.

 


Does Corn Still Need Rescuing?

The 2015 Illinois corn crop continues to develop on schedule, with 75% of the crop having reached silking by July 19. But the crop condition rating continues its steady downward trend, with the good + excellent percentage now at 55%, down from its high of 79% at the end of May. Virtually all of this decline is due to standing water, past or present.

Rainfall frequency and amount has moderated some, but parts of western Illinois have received more than 6 inches so far in July. Growing degree accumulations since May 1 are running close to average for the whole state. With planting a little ahead of normal this year we can expect the crop to reach maturity beginning in early September or even late August.

Soil samples pulled at tasseling at several sites in our NREC-funded N-tracking project show that soil N levels have fallen considerably in recent weeks, to levels at or below 50 lb N per acre in the top two feet. We’re finding that soil N levels tend to go down to 40 to 50 lb and not much below that. That’s in part because roots don’t “find” all of the N that’s there, and in part because the mineralization process continues to release N into the soil. When soil N levels are this low, we’re finding much of the N to be in the ammonium form, which is the form produced by mineralization.

For the crop that is well past pollination, the number of kernels developing per ear is an indicator of maximum yield potential. Crops with badly damaged root systems have in most cases been showing pale or yellow leaves, death of lower leaves, and stunting, and either show no ears at all or have very low numbers of kernels. Their yield potential is low and can’t be improved.

In some cases the crop is only now starting to show loss of green coloryellowing, including lower leaf firing that may be moving up the plant. Some of this is occurring in parts of Illinois that have started to dry out, so where we expected the crop to be starting to recover. This still seems to be occurring mostly in lower parts of fields, where water may have stood temporarily, perhaps several weeks ago.
It seems logical to think that N deficiency developing now in fields where standing water hasn’t been a big concern is due to loss of N finally showing up as the plant continues to take up N. There certainly might be some of that happening. Another possibility is that limitations of the root system from earlier damage are only now showing up, especially as the surface soils start to dry and roots start to draw water from a little deeper in the soil.

Can we know which is the case, and is there anything we can still do about it? Either of the situations might mean the crop could respond to N applied to the surface, as long as the N can get into the plant. Before spending the equivalent of about 10 bushels of corn to apply urea by air, though, it would be good to try to assess the yield potential and to try to figure out if the crop is in good enough condition with enough kernels to make a return on the investment likely. There’s no sure indicator of the potential of the crop to respond, but as a start it should have most leaves still intact and around 450 to 500 kernels developing per ear.

If a decision is made to apply more N to a field, the rate should be restricted to no more than 40-45 lb and the N should be applied as soon as possible. Protecting urea with Agrotain should help reduce volatility, but if urea stays on the surface long enough (without enough rain to move it into the soil) it is not going to get into the plant to do much good anyway. Foliar N (urea-formaldehyde solution) is another possible source of N. The lower rate of N applied (usually 10 lb per acre or less) might be enough to carry the crop until its roots can take up more N from the soil. With any source, the idea is to keep deficiency from advancing; the amount of green leaf area is closely tied to grainfilling rate. Dribbling UAN could work, but getting it into tall corn without delay in fields with wet spots might be difficult.

Even if temporary N deficiency can be relieved by supplemental N applied this late, N will not prove to be the most limiting factor; yield prospects will depend mostly on the ability of the root system to continue to take up water, and along with it some N, through the next month to 6 weeks. Some of the developing N deficiency that we are seeing now may be the result of root systems that are damaged more than we think. In that case even moderate stress as surface soils dry out might send plants into a downward spiral. There’s no good diagnostic for root system intactness, but pulling a few plants might provide a hint. If root systems seem small, shallow, or have darkened areas and dead root tips, the prognosis isn’t great.

Things are looking better in parts of the state or fields where water hasn’t stood recently and where roots are getting some oxygen. Outside the downpours, the weather continues to be good, without high temperatures so far. More low-humidity days would help, but humid days with sunshine are still helping the crop. It’s not 2014, when temperatures this time of year were well below normal. But pollination and kernel set should at least be normal in undamaged parts of fields. Let me know if you see something different.

 


2015 Field Day July 22 at Orr Ag Center, Perry

The 2015 Orr Center Field Day presented by the Department of Crop Sciences at the University of Illinois will be held on Wednesday, July 22 at the Orr Center, which is located on Route 104 four miles west of the junction of Illinois Routes 104 and 107.

Tours will start at 9:00 AM, by group with the last group leaving by 9:20. The tour will take about two hours, and will be followed by lunch provided by UI Extension.

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

  • Angie Peltier: Management of Sudden Death Syndrome in Soybean
  • Aaron Hager: To Mix or to Rotate? – Herbicides and Weed Resistance
  • Jake Vossenkemper: Soybean Varietal Maturity and Planting Date
  • Stacy Zuber & Mollie Adams: Do Crop Rotations Affect Soils?
  • Emerson Nafziger: Are We Getting Better at Managing Nitrogen?

For more information call Mike Vose at 217 236-4911 or by email at mvose@illinois.edu


Statewide Survey of First-Generation European Corn Borer Confirms Exceedingly Low Population

As part of our on-going USDA NIFA (National Institute for Food and Agriculture) sponsored University of Illinois Extension IPM Program, our research team, led by Nick Tinsley (Postdoctoral Research Associate, Department of Crop Sciences), surveyed 28 counties between June 10 to 22 for first-generation European corn borer injury. The counties and six regions surveyed are listed below.

Regions and Counties Surveyed

Northwestern Illinois: Bureau, Knox, Mercer, Ogle and Whiteside
Northeastern Illinois: Kane, Kankakee, LaSalle, Livingston and McLean
West-central Illinois: Adams, Fulton, Logan, McDonough and Morgan
East-central Illinois: Christian, Clark, Effingham, Piatt and Vermilion
Southwestern Illinois: Bond, Jackson, Macoupin and St. Clair
Southeastern Illinois: Gallatin, Jefferson, Lawrence and Massac

Five cornfields were randomly selected in each county and within each field, 100 consecutive whorl-stage plants were sampled for any signs of whorl feeding or the presence of European corn borer larvae. An action site was sampled for European corn borer moths near each field by making 100 sweeps with a standard insect sweep net. We characterized action sites as dense stands of tall grasses in roadside ditches or nearby waterways. Within these action sites moths congregate and mating occurs.

 

European corn borer action site.

European corn borer action site.

 

Remarkably, no European corn borer moths were recovered at any of the 140 locations (28 counties X 5 fields) in spite of making a total of 14,000 sweeps! Of the 14,000 whorl-stage plants examined, only 68 had shot-holing (evidence of first-generation injury). The mean percentage of plants with first-generation whorl feeding by region was very low: East-Central – 0.28%, Northeast – 0.56%, Northwest – 0.64%, Southwest – 0.75%, Southeast – 0.25%, and West-Central – 0.44%.

The extensive use of highly-effective Bt hybrids and the areawide suppression brought about by these transgenic hybrids is the primary explanation for these very low densities of European corn borers. According to USDA ERS (Economic Research Service), the use of “stacked gene varieties” accounted for 88% of the corn grown in Illinois during the current growing season. The stormy weather pattern that enveloped much of Illinois during our sampling efforts also likely contributed to the poor establishment of the first-generation of borers.

During some of my summer meetings, a few producers mentioned they had discovered first-generation borers in their non-Bt cornfields. To some extent, this observation caught them by surprise. Although the overall European corn borer population is down across Illinois, this once prominent insect pest flourished for decades (prior to the widespread adoption of Bt hybrids) in many cornfields each season across the Corn Belt. Where non-Bt corn is grown, European corn borers have the potential to infest these fields and cause losses. Therefore, don’t neglect to scout those fields carefully and be prepared to apply a timely rescue treatment. To date, there is no evidence of field-level resistance development by European corn borers to Bt hybrids. This is a remarkable success story nearly 20 years after the commercial release (1996) of Bt hybrids aimed at this insect.

Mike Gray, Professor and Extension Entomologist

 

 

 

 

 


Northern Illinois Agronomy Day, July 9th

The Northern Illinois Agronomy Research Center will be hosting its summer Agronomy Day on Thursday, July 9th in Shabbona. Join University of Illinois Extension specialists and researchers as they address issues pertinent to the 2015 crop growing season.

The program begins at 9:00 a.m. and will finish with a noon meal provided at no cost. It is open to all who wish to attend and there is no registration fee. Certified crop adviser continuing educational units will be available.

More than 40 individual research projects encompassing corn, soybean, wheat, oats and cover crops are under way. Current studies include evaluating crop rotations, date of planting, row spacing, plant populations, crop diseases, variety comparisons and crop nutrient management.

Weather permitting; presentations will take place outside, next to research plots. Guests will be transported by tour wagons. Field topics include:

• Water, Corn, and Nitrogen – Can the 2015 Crop Survive and Thrive? – Dr. Emerson Nafziger, Professor and Extension Specialist, Crop Production
• Field Crop Insect Surveys and Management Update – Dr. Mike Gray, Professor and Extension Specialist, Agronomy Research Center Entomology, and Assistant Dean for ANR Extension Programs
• Herbicide Identification: Crop Injury Symptoms and Weed Control – Dr. Greg Steckel, Research Agronomist, NIARC
• Introduction/Update of the Illinois Nutrient Loss Reduction Strategy – Dr. Mark David, Professor Water Quality and Biogeochemistry, Dept. of Natural Resources and Environmental Sciences
• 2015 Weed Control Challenges – Doug Maxwell Principal Research Specialist, University of Illinois Department of Crop Sciences

The 160-acre Northern Illinois Agronomy Research Center is located north of Shabbona and has been used for crop research since 1948. It is the northernmost research center within the University of Illinois Crop Sciences department that is dedicated primarily to row crop research. Visitors are always welcome.

The research center is located at 14509 University Road, about a half mile east of Shabbona on U.S. Route 30 then then 5 miles north on University Road. Perry Road, which runs from the Steward exit (#93) on I-39 to south of DeKalb, is a quarter mile north of the Center. For more information, contact Russ Higgins at 815-274-1343 or email rahiggin@illinois.edu.


Corn disease update and farewell

Last week, I visited all of the University of Illinois corn variety trials in the northern half of the state.  Gray leaf spot and northern leaf blight were beginning to appear in most of the locations, but were the most obvious at the trial located near Perry, IL (Pike County).

DSCN0119

“Young” lesions of northern leaf blight beginning to develop on a corn leaf.

DSCN0128

Gray leaf spot lesions developing on a corn leaf.

With the amount of rainfall received in the past few weeks, it is not surprising that these diseases were beginning to appear.  Since hybrids differ in their level of susceptibility to these diseases, not all hybrids in the trials had symptoms.  If the rainy conditions continue, then a foliar fungicide application sometime between tassel emergence and silking may need to be considered on hybrids that are the most susceptible.  Some general guidelines that may help make a foliar fungicide application decision follow:

  • On susceptible to moderately-susceptible hybrids:  consider a foliar fungicide if disease is present on the third leaf below the ear or higher on 50% of the plants prior to tasseling.
  • On intermediate hybrids:  consider a foliar fungicide if the field has a history of disease, if the previous crop was corn with at least 35% of the ground covered with residue, if disease is present on the third leaf below the ear or higher on 50% of the plants prior to tasseling, and if warm and humid weather has persisted.
  • On moderately-resistant to resistant hybrids:  foliar fungicides generally are not recommended, but scouting is important to confirm that diseases are not present.

The presence of diseases does make a difference in how profitable a fungicide application may or may not be.  From trials conducted at the University of Illinois from 2008 to 2014 at many environments (45 total environments) in Illinois, the results indicate that the overall yield response to foliar fungicides was 5.3 bushels/acre (see chart below).  However, this yield response was 9.5 bushels per acre when disease developed to affect at least 10% of the leaf area in untreated controls (in 17 of the environments).  In situations with low disease severity (disease developed to less than 10% of the leaf area in untreated controls), the average yield response was only 2.8 bushels per acre (in 28 of the environments).  Obviously, the marketing price of corn and the fungicide and application costs will determine if fungicide applications were profitable.  The chart below shows the profitability of fungicide applications under different yield response goals (3, 5, 8, and 11 bushels per acre).  The bottom line is that it takes a higher yield response to be profitable when corn marketing prices are lower.

Corn fung results 2014

Results from University of Illinois corn fungicide trials conducted from 2008 to 2014. All applications were made at tassel emergence (VT).

On a final note, my last day at the University of Illinois is today (June 30).  I will be moving to a similar position at the University of Kentucky, and will be based out of the Princeton Research and Education Center in the western part of Kentucky.  I want to thank the University of Illinois for my opportunities here and thank many of you for your support and interest.  There are no current plans to replace my position as Extension Plant Pathologist at the University of Illinois.  If you have field crop disease questions, the following contacts may be useful:

University of Illinois Plant Clinic

1102 S. Goodwin Ave.

Urbana, IL 61801

Tel: 217-333-0519

Email: plantclinic@illinois.edu

 

Commercial Agriculture Extension Educators:

Robert Bellm

Brownstown Agronomy Research Center

1588 IL 185

Brownstown, IL 62418

Tel: 618-427-3349

Email: rcbellm@illinois.edu

 

Dennis Bowman

Crop Sciences Research and Education Center

1102 S. Goodwin Ave.

Urbana, IL 61801

Tel: 217-244-0851

Email: ndbowman@illinois.edu

 

Russ Higgins

Northern Illinois Agronomy Research Center

14509 University Road

Shabbona, IL 60550

Tel: 815-824-2029

Email: rahiggin@illinois.edu

 

Angie Peltier

1000 North Main Street

PO Box 227

Monmouth, IL 61462

Tel: 309-734-5161

Email: apeltier@illinois.edu


Stink Bugs Observed in Soybean Fields of Southwestern Illinois

Byron Hendrix, Agronomist with Terayne AG Specialties, Venedy, IL, observed green and brown stink bugs in soybean fields in Washington County on June 25. The field in which stink bugs were observed was planted in early May. Management of stink bugs in vegetative stage soybeans is not typically necessary. As plants enter the reproductive stages of development and pods begin to fill, rescue treatments may be warranted. Growers should consider a rescue treatment when adult bugs or large nymphs reach densities of 1 per foot of row when pods are filling. As soybean fields begin to flower, they can become very attractive to stink bugs.

Adult green stink bug, Washington County, Illinois, June 25, 2015 (Courtesy of Byron Hendrix, Agronomist, Terayne AG Specialties, Venedy, Illinois).

Adult green stink bug, Washington County, Illinois, June 25, 2015 (Courtesy of Byron Hendrix, Agronomist, Terayne AG Specialties, Venedy, Illinois).

 

The holes in the soybean leaves (above photograph) appear to be the work of insect defoliators (e.g. bean leaf beetles). Stink bugs have piercing and sucking mouthparts which they use to remove fluids from plants. Stink bugs may feed on stems, leaves, blossoms, and seeds of soybean plants. They prefer the newest growth and developing seeds. As the season progresses, producers should continue to monitor soybean fields for this insect pest.

Mike Gray, Professor and Extension Entomologist


Western Corn Rootworm Adults Present in Some Central Illinois Fields

In spite of the very heavy precipitation and saturated soils in many fields across the state, some western corn rootworm adults have survived and have been sighted in several fields in central Illinois. Matt O’Whene, Research Associate with DuPont Pioneer, observed western corn rootworm adults in a cornfield located in Piatt County on June 24. The western corn rootworm in Matt’s photograph appears to be a male. Males typically emerge first followed by the emergence of females a few days later. By late next week, I expect sightings of western corn rootworm adults to become much more common. It remains to be seen how much root injury will occur this year, especially in areas of the state where resistance to some of the Cry proteins (Cry3Bb1 and mCry3A) has been confirmed. Plants may be more susceptible to lodging this season due to saturated soils, shallow root systems, and frequent storm activity accompanied by windy conditions. As plants become increasingly top heavy, I anticipate more calls related to lodged fields. Don’t automatically assume that lodged fields have root injury associated with rootworm feeding. The only way to confirm corn rootworm larval injury is to dig up plants, wash the soil from the root system, and evaluate the roots for feeding and pruning. We typically wait until mid-July to begin rating roots for injury in our product evaluation trials.

Male western corn rootworm adult, Piatt County, Illinois, June 24, 2015 (Courtesy of Matt O’Whene, Research Associate, DuPont Pioneer).

 

In addition to observations of western corn rootworm adults in Piatt County,  Preston Schrader, Monsanto Company, and Jeremy Lake, Technical Agronomist Asgrow/DeKalb found adults in Macoupin County on June 22. Preston Schrader also indicated adults had been sighted in Menard County. Bottom line — adult emergence is underway and in the coming weeks, it will be time to evaluate the performance of root-protection products (Bt hybrids and/or soil insecticides).

Mike Gray, Professor and Extension Entomologist


Corn Rootworm Emergence Just Around the Corner for East Central Illinois

Joe Spencer, an entomologist with the Illinois Natural History Survey, observed 2nd and 3rd instar corn rootworm larvae earlier today (June 23) in his research plots located north of Urbana, Illinois. He anticipates the emergence of adults from these plots by early next week. As we begin the 4th of July Holiday, I suspect initial sightings of western corn rootworm adults will begin to occur across central Illinois. Overall, I anticipate the statewide population of western corn rootworms to be reduced this season due to the heavy precipitation many areas have received throughout June leading to saturated soils at the time of larval hatch.

Corn rootworm larva in non-Bt plot north of Urbana, Illinois, June 23, 2015 (Courtesy of Joe Spencer Illinois Natural History Survey).

Corn rootworm larva in non-Bt plot north of Urbana, Illinois, June 23, 2015 (Courtesy of Joe Spencer Illinois Natural History Survey).

 

On June 11, 2015 I observed a few Japanese beetles in cornfields scattered across western and central Illinois counties. In recent years, densities of this pest have been most significant in northwestern Illinois. If you begin to observe western corn rootworm adults in your area of the state, please let me know and I will pass along your observations to readers of this Bulletin.

Mike Gray, Professor and Extension Entomologist

 


Armyworms Inflict Damage to Corn in Northeastern Illinois

On June 8, I received a report from Stephanie Porter, Burrus Sales Agronomist, concerning a severe infestation of armyworms in McHenry County. Significant damage had been inflicted to a field of no-till corn in which rye had been used as a cover crop. Throughout my career, the most common reports of damaging infestations of armyworms have occurred in corn when rye has been used as a cover crop. For more information on the biology, life cycle and management of this pest, please refer to the Department of Crop Sciences fact sheet regarding this insect.

 

No-till corn planted into a rye cover crop, McHenry County, June 8, 2015 (Courtesy of Stephanie Porter, Burrus Sales Agronomist).

No-till corn planted into a rye cover crop, McHenry County, Illinois, June 8, 2015 (Courtesy of Stephanie Porter, Burrus Sales Agronomist).

 

Armyworm defoliation in no-till cornfield following a rye cover crop, McHenry County, June 8, 2015 (Courtesy of Stephanie Porter, Burrus Sales Agronomist).

Armyworm defoliation in no-till cornfield following a rye cover crop, McHenry County, Illinois, June 8, 2015 (Courtesy of Stephanie Porter, Burrus Sales Agronomist).

 

Armyworms in no-till cornfield following a rye cover crop, McHenry County, Illinois, June 8, 2015 (Courtesy of Stephanie Porter, Burrus Sales Agronomist).

Armyworms in no-till cornfield following a rye cover crop, McHenry County, Illinois, June 8, 2015 (Courtesy of Stephanie Porter, Burrus Sales Agronomist).

According to the Entomological Society of America (ESA) Handbook of Corn Insects page 50

“Armyworm larvae may feed only on leaf margins, or they may strip the plants, leaving only the stalks and leaf midribs. A corn plant recovers from this injury when feeding activity is moderate, as long as the growing point of the plant has not been injured. However, entire cornfields can be defoliated when an armyworm infestation is heavy and feeding damage is severe.”

I offer my thanks to Stephanie Porter for sharing this information and photographs.

Mike Gray, Professor and Extension Entomologist