Watch Corn For Late Season Insects And DiseasesWarns Specialist

SPRINGFIELD, MO.

 As the corn season moves forward, producers need to watch for late season pests according to Jay Chism, University of Missouri Extension agronomy specialist in Barton County.

   “Several corn fields have been damaged by fall army worms. Late planted corn and milo are at the most risk,” said Chism.

   Treatment is justified when 75 percent or more of the plants have whorl damage and larvae are present in the whorls. Ground applied sprays directed over the row are recommended for best control of this pest.

   “Many times fall army worm is just superficial damage that does not require control measures,” said Chism. “However, several fields this season have damage at the threshold level and small worms are still present in the whorls.”

   If the worms are small, less than a one-half inch, the pest will continue to feed and may damage the corn tassel before it emerges. Many times only 25 to 30 percent control is all that can be expected when insecticide applications are used. “Southern corn rust, a foliar disease, is another pest that requires farmers to watch their crops,” said Chism.

    “Southern rust has been reported in Kansas, but to date it has not been reported this season in Missouri.”

  Southern rust is favored by warm, humid conditions and the spores must be blown in from southern locations. Southern rust pustules are found primarily on the upper leaf surfaces, less frequently on lower leaf surfaces.

   When southern rust is severe, leaves and leaf sheaths may yellow and die prematurely. Damage tends to be more severe on late-planted corn or late-maturing hybrids.

   “It is important to watch the ear leaves, if lesions are found the fungus can spread rapidly under the right weather conditions,” said Chism.

   Chism has sent leaf samples into the MU Diagnostic Lab to be sure that the disease has not slipped in. Southern rust is difficult to distinguish from common rust.

   “Common rust does not typically require control, so it is important to make the correct diagnosis before deciding to apply a fungicide,” said Chism.

For more information about corn pests, contact Chism at the Barton County Extension office at (417) 682-3579. Δ