Goss's wilt is not a new disease. It's been causing significant yield damage across Colorado and Nebraska since 1969. In recent years Goss's wilt has been moving eastward across the Corn Belt. It has reached Indiana and spread north to the Canadian border.
"Goss's wilt has a long history of wreaking havoc in cornfields in the western Corn Belt, but this disease continues to expand its boundaries," says Scott Heuchelin, Pioneer research scientist and plant pathologist.
Signs and symptoms
The disease causes significant leaf loss, hurts stalk quality and reduces yield. Goss's wilt overwinters in infected corn residue and is spread through water, particularly when infected water splashes onto equipment and vehicles. Once in a field, it enters plants through wounds caused by hail, heavy rain, sand blasting, wind or other means.
"Thunderstorms and other weather systems can spread this disease," says Alison Robertson, an Iowa State University associate professor of plant pathology and microbiology. "These events can cause entry wounds and contain moisture that can carry the pathogen."
It's easy to confuse the symptoms of Goss's wilt with other environmental conditions such as drought stress, sunscald or nutrient deficiencies. The first step is to scout fields to spot the distinguishing characteristics. Corn can be infected at any growth stage, so it's important to inspect fields early and continue through midseason growth.
What to look for
In the seedling stage, early infection of Goss's wilt can be systemic and result in discolored vascular tissue with slimy stalk roots. There will also be a buildup of bacteria in the vascular bundles. This inhibits the plant's ability to transfer water. Growth is stunted. The plant eventually may wilt and die as if drought stressed.
Midseason signals and symptoms include distinct dark green to black "freckles" on or around leaf lesions. Shiny or glistening patches of dried bacterial ooze, similar to a thin layer of varnish, often are present. Additional signs of infection include water-soaked streaks or tan-to-gray lesions running lengthwise up the leaves.
"Fields most at risk for infection include those with continuous corn, grassy weeds, surface crop residue and those managed with minimum or no-till practices," Heuchelin reports.
To help control the disease, growers should manage field debris, the primary source of the pathogen. Crop rotation is another helpful strategy, and cleaning equipment before moving to another field can also help limit the spread of Goss's wilt.
In-season management options are limited. "Goss's wilt is a bacterium; therefore, it cannot be controlled by a fungicide," Robertson reports. "The best strategy is to plant resistant genetics."
Choose a hybrid with a high level of Goss's wilt resistance, especially if the field has a history of infection. Pioneer has conducted decades of research and has been breeding for Goss's wilt resistance in the western Corn Belt. Breeders have developed highly resistant corn germplasm.
Most research has occurred at La Salle, Colo., near the heart of Goss's wilt's traditional home. However, researchers have identified key resistance genes and incorporated them into hybrids for a wide variety of maturities, including those farther east. This gives Pioneer customers sound options for protection against Goss's wilt.