By Wayne Flanary, MU Extension Field Specialist in Agronomy

Several growers recently received grain dockage and were trying to determine the cause. A sample was taken to the Missouri Department of Agriculture, Grain Inspection Service, in St Joseph and they identified the sample kernels as “cob rot.”

The sample was sent to the University of Missouri Plant Diagnostic Clinic to determine what organism caused damage. The organism plated out was Diplodia. The second organism did not sporulate, so the identity was determined by molecular DNA. The organism in the grain was identified as Diplodia ear and stalk rot.

Conditions such as dry weather before silking then wet conditions can increase risk of disease. Continuous corn increases risk as inoculum resides on crop residue. Hybrids can be susceptible so care should be given in hybrid selection. Harvest grain as soon as possible.

Diplodia infected kernels can be fed to livestock, however, please check grains for mycotoxins as other kernel rots may not be suitable for feed. This sample may not represent your grain. Samples can be sent to the Plant Diagnostic Clinic (https://extension.missouri.edu/programs/plant-diagnostic-clinic/sample-submission) for identification and mycotoxins can be analyzed by MU Veterinary Laboratory (https://vmdl.missouri.edu/toxicology/mycotoxin-screen-in-feedstuffs/). There are fees for services.

Grain dried to 15 percent moisture will stop Diplodia, but other organisms may invade the grain through the infected Diplodia kernels. Dry grain to 14 percent moisture and cool grain to below 50°F as soon as possible. Infected grain should be stored at 30°F as we move into winter.  No infected grain should be held during summer.

For more information, contact Wayne Flanary, Field Specialist in Agronomy, University of Missouri Extension, at 816-279-1691 or cell phone 913-220-3670.