Seedling diseases in soybean more evident throughout the state

With the storm that moved through the state the past week, it is not surprising that we are seeing more seedling diseases in soybeans.  In many cases Rhizoctonia has been identified as the causative organism, alone or in combination with other soil issues such as compaction.  Rhizoctonia is one of the most common and problematic seedling issues for soybean producers in Illinois, and can cause significant yield losses due to stand reduction and reduced plant growth.  In addition to killing germinating and emerging seedlings, Rhizoctonia can produce stem cankers.  Cankers are sunken lesions that  are

Rhizoctonia cankers on lower stems of soybeans. Image Credit B Nelson.

 

A characteristic canker on the lower stem of a soybean plant.  Image CPN.

typically located at or near the soil line, although sometimes they can extend a couple of inches up the lower stem.  Large cankers can severely reduce the translocation of water and nutrients up the stem, causing the plant to wilt and potentially die.   Affected plant tissues tend to appear reddish-brown and will have a corky, almost dry-rotted look to them.  Rhizoctonia typically appears in patches, and is most problematic when soils are moist and warm.  Seed treatments with active ingredients that are effective for Rhizoctonia can be effective for reducing early infections.  However, these products are only effective for the first week or two after planting, and are unlikely to impact disease occurring later in crop development.  Varieties differ in their tolerance, but there is no resistance to Rhizoctonia.

 

Another pathogen that we may start to see more of in the upcoming days is Phytophthora.  Phytophthora lesions on stems are black to brown and extend from the roots up the lower stem of the plant.  Margins are not as defined as in Rhizoctonia-infected plants, and lesions are soft and mushy.  Phytophthora is a water mold and is favored by wet, saturated soils.  When soils are saturated and warm, the overwintering structure of this pathogen germinates, producing another structure that releases small spores into soil solution.  These spores have tails, or flagellae, that propel the spores in the water.  Then, the spores sense gradients in chemicals from plant roots to locate and infect root systems.  A video of these spores in action can be found by clicking here.  Phytophthora tends to be found in low lying, poorly drained areas of the field.

Phytophthora stem lesions on soybean. Image CPN

 

Management of Phytophthora starts with the selection of a resistant variety.  There are two types of resistance available for management of Phytophthora, race-specific (Rps) and partial.  Race specific is similar to a door that will completely block specific types of Phytophthora from infecting plants.  However, some individuals contain a key that allows them to open that door and infect roots.  Thus, if a variety with an Rps gene (door) is planted into a field with a Phytophthora population that is comprised of individuals able to overcome (key) that resistance, you may still see significant infection.  The most common Rps genes are Rps1a, Rps1c, Rps1k, Rps3a, and Rps 6.  Although many varieties only have a single Rps gene, some have multiple, or stacked Rps genes.  Partial resistance acts like bouncers guarding the stage at a concert.  They provide some resistance to all populations of Phytophthora, but some disease, typically less and developing at slower rates, can be caused (rowdy fans who eventually jump on stage, only to be pulled off soon thereafter).  Partial resistance is not expressed until later in plant development, typically after V1, and therefore are not effective for managing early infections.  Like Rhizoctonia, seed treatments can provide benefits early in the season.  It is important to realize that Phytophthora is not a true fungus, but an oomycete, and therefore seed treatments must contain oomycete- specific active ingredients (e.g. metalaxyl, mefanoxam, ethaboxam).

 

 


Seedling Diseases in Soybeans – Time to Scout!

Now is the time that seedling diseases of soybeans will start to be apparent.  Indeed, we have started to see more images of soybeans that may have symptoms of seedling disease.  However, it is important to understand that seedling diseases are complex, and a simple picture often is not sufficient to adequately diagnose the issue.  I wrote a more extensive of seedling diseases of soybean on the Illinois Field Crop Disease Blog, which can be accessed here


New Crop Protection Network Publication on Proper Fungicide Use for Fusarium Head Blight Now Available

The Crop Protection Network is a free, online resource for producers and those in the agronomic community interested in diseases of field crops and their management.  Recently, CPN started adding resources to the site to include diseases of small grains such as wheat.  As part of this effort, we published a publication on how to optimize fungicide applications for Fusarium Head Blight management.  The publication can be accessed for free at the CPN library


Diagnosing disease related issues in the field

Well, it is that time of year where we start to see issues developing in the field.  Questions such as, “What happened?”  and  “Why me?” will become more common.  The key to managing diseases is proper diagnosis, and this starts in the field.  In my recent post on the Field Crop Disease Blog, I provide several tips for diagnosing issues in the field, and distinguishing disease related problems from abiotic issues.  Check out the post, and sign up for updates!


Optimal Use of The Fusarium Head Blight Prediction Tool

With the recent rain blast and rain forecast in the next week, coupled with the wheat crop starting to move into flowering within the next 7-14 days, it is important to start thinking about Fusarium head blight risk.  I recently wrote an expanded article on the use of the FHB prediction tool that can be found by clicking here.

Some early flowering varieties will likely flower by the weekend.  Most varieties are near flag leaf and will require another 7 – 10 days, depending on weather, before they will begin to flower.


Update on wheat in Illinois

This past week we spent a few days surveying wheat fields throughout the state in order to see how the crop is progressing as well as better understand what disease related issues we may be experiencing.  Most of the crop was near flag leaf emergence (Feekes growth stage 8/9) with a few fields near boot in locations further south.  The good news is that of the 26 fields we looked at, none had any stripe rust, nor have I received any additional reports of this disease in the state.  In general, diseases were minimal.  In southwest portions of the state Septoria leaf blotch (aka speckled leaf blotch) was fairly common.

Septoria (speckled) leaf blotch is often found in the lower canopy when conditions are cool and humid. Photo N Kleczewski

 

This is a residue-borne disease that is favored by cool, wet conditions and can grow and persist on small grain residues.  The disease is often located deep within the lower canopy, and causes irregular brown lesions on the foliage.  At the center of the lesions you will often see black structures that may resemble tiny peppercorns.  These structures are why the disease has the extremely creative common name speckled leaf blotch.  The disease spreads upwards predominantly via rain splash, and seldom causes significant yield impacts.  This typically is due to increased temperatures that do not favor disease development as the crop develops and the flag leaf is produced.  Remember, the flag leaf and green tissues above contribute the majority of carbohydrates for grain fill (over 70% from the flag leaf alone).  Foliar diseases that do not reach these tissues are typically not a major concern.

Similarly, I came across a few fields with light powdery mildew.  Unlike Septoria leaf blotch, powdery mildew is an obligate pathogen and requires a living host to grow and reproduce.  Cool, humid (not wet) conditions favor powdery mildew development.  In general, production practices that favor rapid plant growth and lush, full canopies early in the season favor this disease.  For example, high nitrogen rates or manure use can result in rank growth early in the season.  Powdery mildew can reproduce more quickly than Septoria, and therefore can occasionally impact early season growth or tillering in some instances.  Although I did not see anything that would be of concerns and have not had any reports of severe powdery mildew, management is best achieved through selection of a resistant variety and avoiding excessive nitrogen application.   Early season fungicide applications with nitrogen applications can have some benefit when a field is at high risk for disease (i.e. susceptible variety, heavy N use, disease present early, cool weather forecast for several days/weeks) but are not recommended if disease is low.  Anything in the triazole (FRAC group 3), SDHI (FRAC group 7) or Strobilurin (FRAC group 11) fungicide classes will help control powdery mildew in high risk situations.

As we approach boot and heading you should keep an eye on the Fusarium Head Blight Prediction Center for updates on disease risk.  I will follow up with a post on how to best use this tool on my blog in the next few days. Forecasts are calling for e moderate and potentially rainy conditions over the next 7-10 days  depending on your location.    In the meantime, keep an eye on your fields, and enjoy the weather!

 

Nathan Kleczewski Extension Field Crop Plant Pathologist University of Illinois   email:  nathank@illinois.edu


Stripe Rust in S. Illinois

I received notice of stripe rust in S. Illinois today.  Stripe rust is an important disease affecting wheat.  Please find an article on this disease and management by clicking here.  

If you locate stripe rust in your field please tweet a picture to me (@ILplantdoc) or email (nathank@illinois.edu) with the wheat variety, growth stage, and approximate percent of field infected.  This information will be useful to IL wheat producers this year and in upcoming seasons.

An example of a stripe rust in wheat. Photo N. Kleczewski 2016


Join us for the Ewing Agronomy Field Day on Thursday, July 27, 2017

The University of Illinois Extension will host the Ewing Demonstration Center Agronomy Field Day on Thursday, July 27, 2017 at 9 a.m.  Every growing season presents challenges to production, and this year is no exception!  We are happy to host this summer field day to share with local growers current, ongoing agronomy research in southern Illinois, including cover crop trials on corn and soybeans, nitrogen management in corn, weed management in soybean, and our continuous no-till field, now in its 49th year of continuous no-till production.

 

The topics to be discussed at Field Day include:

 

Managing Nitrogen for Corn & 2017 Growing Season Overview

  • Emerson Nafziger, Extension Crop Specialist, University of Illinois

Management Strategies for PPO-resistance

  • Karla Gage, Assistant Professor—Weed Science, Southern Illinois University

Southern Rust Management in Corn

  • Talon Becker, Extension Educator, University of Illinois

Insect Headlines in 2017

  • Kelly Estes, State Survey Coordinator, Illinois Cooperative Agriculture Pest Survey Program

Cover Crops:  The Good, The Bad, and The Practical

  • Nathan Johanning, Extension Educator, University of Illinois

 

The field day is free and open to anyone interested, and lunch will be provided.  Certified Crop Advisor CEUs will also be offered.  The Ewing Demonstration Center is about 20 minutes south of Mt. Vernon 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.  To help us provide adequate lunch and materials, please RSVP to the University of Illinois Extension Office in Franklin County at 618-439-3178 by Monday, July 24.  For additional information on the field day, contact Marc Lamczyk at the number above or lamczyk@illinois.edu.


Cooperators Sought for Insect Trapping Network

Despite the snow falling outside of my window this morning, plans continue for the upcoming survey season. Mother Nature has hinted at spring with temperatures in the 70’s just last week and its time to start thinking about spring insect trapping.

We are starting to look for cooperators that are willing to place and monitor traps for black cutworm and true armyworm this spring and European corn borer, corn earworm, fall armyworm, and western bean cutworm this summer. We provide traps and lures. We ask cooperators to place and check traps several times a week, reporting trap catches to our site.

We will also be looking for cooperators to participate in our summer field surveys as well. This survey is done entirely by the Illinois Cooperative Agricultural Pest Survey Program. Each year, we have conducted a corn and soybean survey, but will also be adding an invasive species component this year. As part of our CAPS program, there are several invasive corn and soybean pests that are a threat. Included in that list are the old world bollworm, Egyptian cottonworm, , cucurbit beetle, brown marmorated stink bug, and kudzu bug in addition to western corn rootworm, soybean defoliators, and other pests. Tar spot of corn and bacterial leaf streak of corn will also be surveyed for.

If you are interested in participating in either of these programs, please use the link below.

https://www.surveymonkey.com/r/C6Q9JGM


Extension Bi-State Crops Conferences in and near Western Illinois

Newer and longer-term partnerships between personnel in Illinois and personnel in Missouri and Iowa have resulted in several bi-state crops conferences to be held during January 2017 in Western Illinois or Eastern Iowa.

 

Friday, January 6, 2017: Bi-State Crop Advantage Conference, Burlington, IA, 8:30 AM – 4:00 PM

Location: Comfort Suites, 1708 Stonegate Center Drive, Burlington, IA.

Hosts: Iowa State University and University of Illinois Extension

More Information: Click here to access the flier.

Online Registration: Click here to register

 

Friday, January 27, 2017: Bi-State Crop Advantage Conference, Davenport, IA, 8:30 AM – 4:00 PM

Location: Rhythm City Casino Resort, 7077 Elmore Ave., Davenport, IA

Hosts: Iowa State University and University of Illinois Extension

More Information: Click here to access the flier.

Online Registration: Click here to register.

 

Friday, January 27, 2017: Western Illinois-Northeastern Missouri No-till Crop Management Conference, Quincy, IL, 8:45 AM – 2:00 PM

Location: John Wood Community College, 1301 S. 48th St., Quincy, IL

Hosts: University of Illinois and University of Missouri Extension, Illinois and Missouri NRCS

More Information: Click here to access the flier.

Online Registration: Click here to register.