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Gray Leaf Spot

Pest Background

  • Gray leaf spot is caused by the fungal pathogen, Cercosporazeae-maydis.
  • This disease is favored by warm temperatures over 80°F, and extended periods of high humidity.
  • Fungal spores overwinter in corn crop residue, increasing chances for infection on non-rotated crops.

 

Identification

  • Gray leaf spot symptoms begin as small brown lesions in the lower canopy, and travel upwards as the season progresses.
  • As lesions expand, they are limited by leaf veins, giving them a distinct, rectangular shape (Figs 1 and 2).
  • Lesions become grayer in color as sporulation begins (Fig 3).
  • Leaves can easily be overtaken by the rapid development of this disease.
Corn leaf displaying GLS symptoms
Fig 1: Corn leaf displaying GLS symptoms
An early GLS lesion, shapes are easier to identify when backlit
Fig 2: An early GLS lesion, shapes are easier to identify when backlit
A sporulating GLS lesion
Fig 3: A sporulating GLS lesion

Management

  • Cultural practices like tillage and crop rotation can decrease inoculum load.
  • Resistant hybrids are available that can tolerate GLS.
  • Fungicides labeled for use on GLS can be sprayed on corn according to the label.

 

References

Crop Protection Network . (2022, January 27). Retrieved from Gray Leaf Spot of Corn: https://cropprotectionnetwork.org/encyclopedia/gray-leaf-spot-of-corn

 

UD Cooperative Extension. (n.d.). Gray Leaf Spot on Corn.Retrieved from Agriculture & Natural Resources: https://www.udel.edu/academics/colleges/canr/cooperative-extension/fact-sheets/gray-leaf-spot-on-corn/

 

Authors: Madeline Henrickson and Dr. Alyssa Koehler


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