Image Courtesy of:
http://www.ipm.ucdavis.edu/PMG/r113100811.html

Last updated by
Nick Dolezal
on April 2nd, 2002

Common Names of Common Corn Rust:

    -Rust
    -Leaf Rust
    -Corn Rust
    -Common Rust

Fungal Causal Agent:

Species:
    Puccinia sorghi

Class:
    Basidiomycetes

Order:
    Uredinales

Host Range:

     Here are some of the alternate crops, ornamentals, and weeds that common corn rust can survive on:
 

Geographical Range:

     Common corn rust can be found throughout the world wherever corn is grown especially in temperate regions of the world. 

Symptoms:

     As seen on photo at the top of the page, corn rust can be detrimental to photosynthesis and overall productivity of a corn plant.  The most obvious symptoms are dark, brownish pustules which can be scattered over the top and bottom of corn leaves.  These pustules can be found on any part of the plant growing above ground but are generally found on the leaves. 

Dissemination:

     The plant pathogen being examined here is generally carried to other plants by wind.  Strong winds carry spores to infect susceptible fields in other areas.  Infected plant material which is transported on machinery can also allow for primary inoculum to spread to new areas.  However, common corn rust spores generally don't survive the midwestern winters.

Disease Cycle: 

     Common corn rust over winters on infected crop residue in warmer regions of the United States.  Uredo spores are blown as primary inoculum and infect northern corn fields.  Rust development and pustule formation then occur and the disease spreads further as more spores are produced.  Mild weather, 60-70 degrees F, and high relative humidity favor common corn rust development.

Control Measures:

      Common corn rust rarely needs control as the pathogen is hit or miss in northern states.  Most problems with common rust are not serious enough to warrant control.  If a problem area has been identified however, some very good common rust resistant hybrids are available and some general resistance is provided by most hybrids on the market.  Fungicides are available for rust control for areas with extreme problems.

Recent Research-Summary:

Related Journal Article:

Gingera,-G.R.; Davis,-D.W.; Groth,-J.V.  1994.  Pedigree selection for improved partial resistance to common leaf rust in sweet corn.  Crop Science Society of America. 34:615-620.

    The reason for the study performed here was observe greater levels of partial resistance to common rust so as to  reduce the need for fungicides to control rust epidemics in sweet corn.  Three sugary sweet corn breeding populations were inbred with selection for rust resistance at each generation.  Plants grown were examined in four field environments for disease severity at five weekly periods.  The results showed that there were significant correlation between ratings of mean disease for two of the five sample periods.  There was also correlation between average disease severity derived from the worst leaf in the plot over five disease sampling periods.  

Sources:

Agrios, George N. 1997.  Plant Pathology 4 ed.  Academic Press.
        pp. 370-378.

Ohio State University Web site.
     http://ohioline.osu.edu/ac-fact/0031.html
 

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