Soybeans and corn seed rot – seedling blight and damping off
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EmailEditor’s note: This article is from the archives of the MSU Crop Advisory Team
Alerts. Check the label of any pesticide referenced to ensure your use is
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One of the most important management decisions in planning for a healthy
crop is to use quality seed. Seed quality affects stand establishment
and seedling rot in both corn and soybeans, particularly when seedlings
are subjected to stress such as excessive moisture and low temperatures.
In addition to quality seed, fungicide seed treatments are also highly
recommended and often not optional. Fungicide seed treatments benefit
stand establishment under adverse conditions such as cool, wet
conditions and where pathogens are present. However, a fungicide seed
treatment will not turn bad seed into good, and it will only provide a
limited benefit under extreme weather and disease conditions.
A number of fungi, fungi-like organisms, bacteria and nematodes can
contribute to seed and seedling rot in corn and soybeans, fungi and
fungi-like organisms being the most significant. These fungi and
fungi-like organisms can be divided into those that are seedborne and
those that are present in the soil.
For soybeans, the soilborne pathogens Phytophthora sojae, several Pythium species and Rhizoctonia solani
are considered to be the most important seedling pathogens in the North
Central states. A study conducted in Iowa concluded that these three
organisms compose 90 percent of soybean seedling diseases. Seedborne
fungi such as Cercospora species, Phomopsis longicola or Fusarium
species can also play a role in seed and seedling disease, particularly
if conditions were poor for seed production in the preceding year. For
more information, see the following websites:
http://www.planthealth.info/seedlings_basics.htm
http://www.extension.iastate.edu/Publications/PM936.pdf
In corn, the soilborne pathogens Pythium and Fusarium species, and Rhizoctonia
are often recorded as causing seedling disease. Given the cool, wet
harvest and high level of ear rot last year, we may see higher levels of
corn seedborne diseases than normal. Seedborne fungi include Fusarium species, Stenocarpella maydis (Diplodia), Penicillium species and Aspergillus species. For more information, visit the following websites:
http://www.ipm.iastate.edu/ipm/icm/2006/5-22/seedhealth.html
http://ohioline.osu.edu/b802/seedling_diseases.html
Corn and soybeans can also suffer from imbibitional chilling injury.
Seeds imbibe water at temperatures above freezing and during seed
imbibition (rehydration) cell membranes can rupture. At cooler
temperatures (less than 50-55°F), seedling metabolism is slow, which
delays membrane repair. Under warmer temperatures, injury through
imbibition is repaired quickly so damage is limited. Imbibition chilling
injury has the potential to kill seedlings, weaken them and slow
development, even in the absence of pathogens. If pathogens are present,
imbibitional chilling damage can predispose seedlings to infection.
Distinguishing imbibitional chilling injury from pathogen damage can be
difficult as the two are difficult to separate.
If you require assistance in identifying the cause of seedling damage, contact Martin Chilvers 517-353-9967 chilvers@msu.edu or submit a sample to the diagnostic clinic: http://www.pestid.msu.edu/
