Pella Chronicle

September 13, 2011

Heat, Drought and Goss’s Wilt Can Affect Corn Yields in Iowa


Iowa Beef Center at ISU

Ames, Iowa — August 31, 2011

Contacts:

Steve Ensley, Veterinary Diagnostic and Production Animal Medicine, 515-294-1950, sensley@iastate.edu

Alison Robertson, Plant Pathology and Microbiology, 515-294-6708, alisonr@iastate.edu

Sherry Hoyer, Iowa Beef Center, 515-294-4496, shoyer@iastate.edu.

Since its initial identification in United States corn fields more than 40 years ago, Goss’s Wilt hasn’t been a serious problem for most Iowa locations. . In the past few years, however, the disease has become more common. This year the bacterial disease was identified in the state much earlier than in past years, prompting some concern among those whose fields previously had not been affected.

Goss’s Wilt is caused by the bacterium Clavibacter michiganensis subsp. nebraskensis (Cmn) which enters the plant through wounds that can be caused by rain, wind, hail, or insect damage. Drought stressed plants may be more susceptible to such wounds, and subsequent bacterial infection, but Steve Ensley of Iowa State University’s (ISU) Veterinary Diagnostic and Production Animal Medicine department said drought stress presents a much bigger potential problem than Goss’s Wilt for livestock producers.

“Nitrate concentration or cyanide concentration in drought-stressed corn can be a serious threat to livestock use,” Ensley said. “Nitrate is converted to nitrite in the rumen, and nitrite converts blood hemoglobin to methemoglobin, which cannot transport oxygen to body tissues. Cyanide concentration, also known as prussic acid poisoning, works in a similar manner. In both cases, animals often die because of lack of oxygen.”

ISU scientists and others said there are no reported issues with feeding Goss’s-infected corn grain, stalks, or silage to cattle, and there is no scientific evidence supporting harm to cattle caused by this bacterium.

Because the Goss’s Wilt bacteria can overwinter in crop residue for several months, continuous corn acres and low- or no-till fields are at higher risk for developing Goss’s Wilt. In a recent article for ISU’s Integrated Crop Management newsletter, ISU plant pathologist Alison Robertson said there are steps farmers can take to reduce the survival rate of the responsible bacterium in future years.

“Research has shown that pure cultures of the bacterium survive less than two months in soil. However, bacteria found on surface crop residue can survive for at least 10 months,” she said. “Some conservation tillage methods including partially burying infected residue should reduce the survival rates. However, soil conservation measures should always be considered. Also, heat, competition with other microbes and low pH reduce the survivability of the bacterium.”

These websites offer additional information:

• Nitrate Toxicity by Nolan Hartwig, ISU Extension Veterinarian

• Reduce Risk of Mycotoxin Contamination by Scouting Fields for Ear Rot by Alison Robertson, ISU Department of Plant Pathology and Microbiology; and Charles Hurburgh, Iowa Grain Quality Initiative

• Goss’s Bacterial Wilt and Leaf Blight by Tamra Jackson, University of Nebraska—Lincoln

• Potential for High Nitrate Levels in Drought-Stressed Corn Silage by Ron Heininger and Jim Dunphy, North Carolina Extension

• Preventing Nitrate Problems in Drought-Damaged Corn by S.D. Livingston, C.D. Coffman and J.C. Paschal, Texas A&M University Extension