TheCropSite.com- news, features, articles and disease information for the crop industry

Gray Leaf Spot


©Purdue University, Plant and Pest Diagnostic Laboratory

Pathogen(s) causing disease:

Cercospora zeae-maydis

Location:

Corn growing areas of the world

Symptoms

Early lesion produced on the corn leaves by Cercospora zeae-maydis are yellow to tan in color and look similar to those produced by other diseases except they have a faint watery halo which can be seen when held up to the light. After about two weeks the lesions appear tan to brown in color and rectangular in shape, bordered by the veins of the leaf. When fully expanded, individual lesions may be 3 to 4 inches long and 1/16 to 1/8 inch wide, depending on the distance between veins.

Conditions:

Infection is favored by extended warm, wet, humid weather. Reports of severe disease infestations are mostly from low lying areas and river bottoms where periods of leaf wetness and high relative humidity are long enough to favor the development and spread of the disease.

Management:

  • Select hybrids with moderate resistance.
  • A two-year crop rotation away from corn is effective if reduced tillage must be maintained for conservation purposes, or a one-year rotation with clean plowing is recommended in fields that have had a problem with the disease.
  • Fungicides are recommended for use on susceptible hybrids planted in fields with a history of gray leaf spot. It is important to apply fungicides early in the season before significant leaf damage has occurred. Thus, scouting fields should be conducted at the V-10 to V-14 growth stage.
  • Control weeds - this will help to increase airflow and dry the canopy faster.

Sources:

Purdue University
The Ohio State University
Bloomberg, Jim. Bayer CropScience Corn Disease Identification Guide PowerPoint. 2009.

Crop Disease Guide

To aid your search, we've included a photo and description along with scouting and management options. And we've also added beneficial insects by crop to help in your identification process.

Choose a Disease

By Crop:

Corn

Wheat

Soybean

Our Sponsors

Partners


Seasonal Picks

Country Dance