Skip Navigation

6/6/2011 - 6/12/2011

Post Emergent Damping Off of Corn Prevalent in Some Fields

Alison Robertson, Department of Plant Pathology, and Erika Saalau-Rojas, Plant and Insect Diagnostic Clinic

Within the past week, we have had several reports of corn seedlings with symptoms of post emergent damping off from a few fields in southern Iowa that were planted in early May.Diseased corn seedlings received at the ISU Plant and Insect Diagnostic Clinic (PIDC) were stunted, compared to health seedlings from the same field (Figure 1), and the mesocotyl was rotted (Figure 2). Affected seedlings occurred in areas of the field where the soil was heavier and consequently wetter (Figure 3).

Survival of young corn seedlings depends on a healthy kernel and mesocotyl which should remain firm and white through at least growth stage V6. Damage to the kernel or mesocotyl prior to establishment of the nodal root system can result in stunted, weak or dead seedlings. A developing corn seedling relies on the kernel endosperm for nourishment until the nodal root system has fully developed, usually around the 6-leaf stage. Thus the mesocotyl acts as the “pipeline” for translocation of nutrients from the kernel and seminal roots to the seedling stalk and leaf tissues. 

Rotted seedlings can be the result of pathogen infections, anhydrous ammonia injury, wireworms and cold injury. Seedling susceptibility to fungal infection increases the longer the seed sits in the ground, and the more stress germinating corn undergoes. Wet and cool (less than 55 F) soil conditions predispose seedlings to infection by a number of fungi.  

We isolated Pythium and Fusarium from the diseased seedlings we received. It is difficult to determine “who got their first”. We suspect Pythium, since the heavier areas of the field were more affected, and we have had periods of cool, very wet conditions this spring. Cool, saturated soil conditions favor infection by this pathogen. There are several species of both Pythium and Fusarium that infect corn and soybeans. Recent work from Ohio has shown that sensitivity to fungicides used as seed treatments may vary within, and across species of Pythium and F. graminearum.


Now is the time to evaluate corn stands

Dig up smaller seedlings and check for symptoms of seedling disease. This will also give you an opportunity to evaluate the effectiveness of the seed treatment that was applied to the seed planted. If you have significant seedling rot, you may have to replant. For replant decisions, please see Roger Elmore and Lori Abendroth’s article on “Assessing corn stands for replanting”.


Figure 1. Variation in seedling size between healthy and affected seedlings
(Photo credit: J Thomsen)



Figure 2. Stunted seedlings have a rotted mesocotyl
(Photo credit: J Thomsen)



Figure 3. Affected seedlings are found in areas of the field with heavier soil
(Photo credit: J Thomsen)


Alison Robertson is an assistant professor in the Department of Plant Pathology with extension and research responsibilities; contact at alisonr@iastate.edu or phone 515-294-6708. Erika Saalau-Rojas is a diagnostician in the Plant and Insect Diagnostic Clinic. She can be reached at 515-294-0581 or pidc@iastate.edu.

Hail on Corn

By Roger Elmore, Department of Agronomy

Corn progress is back on track thanks to recent warm weather. This is indicated by heat unit accumulation for May 1 planting dates hovering slightly above average (107 percent of average statewide). Corn development across the state ranges from about V2 to V9 (second to ninth leaf stages) thanks to the wide range of planting dates this year.

And then thunderstorms hit on June 9 and pounded the corn; some of the thunderstorms were accompanied by severe hail. Plant growing points are still underground for corn plants at V6 (sixth leaf stage) and younger. This fact helps the plants survive early-season hail events even if the leaves are totally destroyed. 

Be patient if your field has hail damage. The short-term weather forecast for warm and sunny weather plus the moisture received from the storms should encourage rapid and healthy regrowth. Plants V6 and younger should survive.  Assess more developed plants carefully.  The following links provide more detailed information:

Hail Industry staging systems differs

Be aware that hail industry corn staging systems differ from the leaf collar system most University Extension and researchers use. Table 2 in the Corn Growth and Development publication provides a comparison. (Click this to order publication on corn growth and development.)

In brief, the ‘horizontal leaf‘ method used by the hail industry is about one to two stages ahead of the leaf collar  system from V2 to  V8. That means a V8 plant in the leaf collar system is similar to a V10 plant in the horizontal leaf system. This is important when you use tables like those included in the University of Nebraska publication referenced above.

For more information other corn issues, see our ISU Extension Corn Production website. Look in the ‘Image Gallery” under ‘Crop Diagnostics’ for images of damaged corn from previous hail events.

 

Roger Elmore is a professor of agronomy with research and extension responsibilities in corn production. He can be contacted by email at relmore@iastate.edu or (515) 294-6655.

Crop Management Clinic Features 20 Management Topics

By Brent Pringnitz, Department of Agronomy

Registration is now underway for the 2011 Crop Management Clinic to be held July 13-14 at the Field Extension Education Laboratory (FEEL) near Ames. The Crop Management Clinic is an intensive two-day training program that focuses on the latest developments in crop production and protection.

Attendees can select from 20 different topics to develop a course agenda that fits their specific interests and needs. ISU Extension specialists will be discussing the impacts of common crop problems, how to avoid them and methods to improve productivity. The curriculum is divided into four primary areas: crop management, pest management, nutrient management, and soil, water and tillage. A detailed listing of scheduled topics is available at the clinic web page.

Sessions are taught by faculty and staff from the departments of agronomy, agricultural and biosystems engineering, entomology and plant pathology, in addition to guest instructors from surrounding states. Each small-group session includes hands-on training in FEEL demonstration plots to provide a setting for instructor-student interaction.

The Crop Management Clinic is approved for up to 12 Certified Crop Adviser CEUs. Credits in each CEU category are dependent on sessions selected by the student.

Registration is required for this program and space is limited. Registration is $250 and includes lunches, breaks and course references. To register for this program, or for more details on the course, visit the FEEL website. For program questions please contact the Field Extension Education Laboratory at (515) 432-9548 or aep@iastate.edu.

The Field Extension Education Laboratory (FEEL) is a 43-acre teaching and demonstration facility that has been training crop production professionals since 1987. FEEL is coordinated by the Iowa State University Corn and Soybean Initiative. For a full listing of educational programs available, visit www.aep.iastate.edu.

 

Brent Pringnitz is an ISU Extension program specialist. He can be reached at  the Field Extension Education Laboratory, (515) 432-9548 or bpring@iastate.edu.

Field Diagnostic Clinic is a Return to the Basics


 

By Brent Pringnitz, Department of Agronomy

The 2011 Field Diagnostic Clinic will be held July 11-12 at the Field Extension Education Laboratory (FEEL) near Ames. This program teraches on the fundamentals of crop plant diagnostics. Sessions focus on insect, weed and crop disease identification, herbicide injury, nutrient deficiency symptoms, and understanding crop growth and development.

For someone new to field diagnostics the Clinic offers fundamental training for making accurate diagnosis of crop and pest problems. The program will also challenge experienced agronomists to identify new pests and crop problems, and refresh skills needed on a daily basis to provide sound agronomic advice.

Sessions are taught by ISU Extension faculty from the departments of agronomy, entomology and plant pathology. Each small-group session includes intensive hands-on training in FEEL demonstration plots, providing a setting for instructor-student interaction.

The Field Diagnostic Clinic is approved for Certified Crop Adviser CEUs: 5.0 crop management, 6.5 pest management and 1.5 nutrient management.

Registration is required for this program and space is limited. Registration is $250 and includes all meals, breaks and course references. To register for this program, or for more details on the course, visit the FEEL website. For program questions please contact the Field Extension Education Laboratory at (515) 432-9548 or aep@iastate.edu.

The Field Extension Education Laboratory (FEEL) is a 43-acre teaching and demonstration facility that has been training crop production professionals since 1987. FEEL is coordinated by the Iowa State University Corn and Soybean Initiative. For a full listing of educational programs available, visit www.aep.iastate.edu.

 

Brent Pringnitz is an ISU Extension program specialist. He can be reached at  the Field Extension Education Laboratory, (515) 432-9548 or bpring@iastate.edu.



This article was published originally on 6/13/2011 The information contained within the article may or may not be up to date depending on when you are accessing the information.


Links to this material are strongly encouraged. This article may be republished without further permission if it is published as written and includes credit to the author, Integrated Crop Management News and Iowa State University Extension. Prior permission from the author is required if this article is republished in any other manner.