Cold, wet conditions increase risk of soil-borne diseases

May 3, 2022 9:48 AM
Blog Post

Brrrrrrrrr.  Is summer ever going to come?  It’s cold.  It’s wet.  Planting progress is behind and everyone is starting to get antsy. When we finally get our seed in the ground, as Emily Unglesbee so eloquently wrote, “a dark, damp basement, teeming with unknown horrors” awaits.

Those unknown horrors include soilborne pathogens, particularly Pythium and the SDS pathogen, Fusarium virguliforme, that thrive in cold wet soils.  Other Fusarium and Rhizoctonia species may also infect seedlings. Infection results in seed rot, root rot (Figure 1) and seedling death, and consequently stand loss.  Seedlings that survive infection are often less vigorous; for corn, this may mean uneven stands in which infected seedlings grow slower than their neighbors and fail to produce an ear.

.Rotted radicles of corn seedlings

Figure1. Radicle root rot of corn caused by Pythium species.  Although these seedlings are likely to survive infection, they may be less vigorous than neighboring non-infected seedlings

What can you do to ensure your crop gets off to the best start?

(i) Wait for good planting conditions

Be patient.  Easier said than done right!

(ii) Use seed treatments

This is the year to be using a seed treatment.  Soilborne pathogens are attracted to germinating seedlings by the exudates the seedlings leak.  The longer the seeds take to emerge, the more time they are susceptible to infection.  Seed treatments contain a mix of fungicides that protect the seed from these pathogens.  As you might expect, the efficacy of seed treatments varies among various pathogens.  The Crop Protection Network has a useful publication that compares the efficacy of commercially available fungicides against various seedling pathogens.

(iii) Scout

Scouting your fields soon after emergence will be important. You’ll want to do stand counts and examine your seedlings for symptoms of seedling disease: rotted seed, root rot, mesocotyl rot (corn), and yellowed, wilted seedlings.  Remember, stand issues can be caused by planter issues or insects (see this article from Erin Hodgson and Ashley Dean).  Understanding what caused your stand problem is important, and can help with crop management in future years

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Authors: 

Alison Robertson Professor of Plant Pathology and Microbiology

Dr. Alison Robertson is a professor of plant pathology and microbiology. She provides extension education on the diagnosis and management of corn and soybean diseases. Her research interests include Pythium seedling disease of corn and soybean and Goss's wilt. Dr. Robertson received her bach...

Daren Mueller Associate Professor

Daren Mueller is an associate professor and extension plant pathologist at Iowa State University. He is also the coordinator of the Iowa State Integrated Pest Management (IPM) program. Daren received his bachelor's degree from the University of Wisconsin-Madison in 1996, and his master's degree a...