This past week several corn samples infected with Goss's wilt were received by the Iowa State University Plant and Insect Diagnostic Lab at Ames. Plant disease specialists at the University of Nebraska also report an increase in the prevalence of Goss's wilt in Nebraska this growing season.
Alison Robertson, ISU Extension plant pathologist and Laura Jesse, entomologist at the ISU diagnostic clinic, offer the following information about this disease. Goss's wilt was first reported on corn in Nebraska nearly 40 years ago; since then it has been reported across the entire Corn Belt. The disease is caused by the bacterium Clavibacter michiganense subsp. nebraskensis. Hosts include corn, green foxtail, barnyard grass and shattercane. The bacterium overwinters on crop debris and in and on corn kernels. Corn plants are susceptible at all growth stages, with optimum temperatures for disease development at 80 degrees F. Infection of leaves, stems and roots occurs primarily through wounds caused by sandblasting, hail, heavy rain or wind.
This corn disease is often misdiagnosed
Symptoms of Goss's wilt being reported in Iowa are leaf blight of leaves at the top of corn plants causing growers to worry about anthracnose top dieback. The disease may also be misdiagnosed as Northern leaf blight or Stewart's disease. Careful examination of the affected leaves reveals large grey to reddish or yellow lesions that extend down the leaf veins. Dark green to black "freckles" are evident within the lesions and are diagnostic of the disease. Often the diseased tissue appears shiny due to bacterial exudate that has dried on the leaves. The bacterium may also infect the xylem (water-conducting) tissues of the plant and result in wilting and death of the plants. If you would like confirmation of Goss's wilt please submit samples to the ISU Plant Diagnostic Clinic at www.plantpath.iastate.edu/pdc/node/158.
Fungicides not effective against Goss's wilt
"There is nothing that can be done this growing season to manage Goss's wilt," says Robertson. "Fungicides are not effective against this bacterial disease." Partially resistant hybrids remain the most effective management tool for this disease, so check with a seed dealer for hybrids that have resistance to Goss's wilt. In fields where Goss's wilt has been a problem, planting a partially resistant hybrid is recommended. Weed management, crop rotation to nonhost crops and tillage to bury infested crop residue are also helpful.