DES MOINES, Iowa, Oct. 6, 2010 - As reports of Goss's wilt continue to expand north and east in corn-growing areas both in the U.S. and now in parts of Canada, growers need to assess its potential impact to help choose resistant lines for next season where the disease is present, say experts at Pioneer Hi-Bred, a DuPont business. These assessments will guide growers' seed decisions for next year and help minimize the potential for yield loss.
"The disease recently has been reported in Colorado, Nebraska, the Dakotas, Manitoba, Minnesota, Iowa, Wisconsin, Illinois and Indiana," says Scott Heuchelin, Pioneer research scientist and field pathologist. "It typically occurs as the result of hail events and storms. When plants sustain abrasion injuries from hail or wind, Goss's wilt bacterium can infect the leaves where they have been damaged. If growers have had hail damage, they should be on alert."
"There are no fungicides that will control Goss's wilt since it's a bacterial disease," says Bill Curran, Pioneer research scientist and corn breeder based in LaSalle, Colo. "While growers can manage the debris, which is the source of the inoculum, and work rotation and tillage into their cropping practices, resistant hybrids are the best way to tackle this problem.
"For more than 25 years, Pioneer has amassed the industry's largest collection of Goss's wilt inoculum," Curran says. "To combat any potential shift in strains of Goss's wilt, we actively collect samples from all over the country and grow the bacterium to use in our screening program.
"In addition to our extensive characterization and screening program in LaSalle, Colo., we're also screening in Fargo, N.D., and Manitoba, Canada, as well as other growing areas reporting issues with Goss's wilt. The knowledge gained in this process, as well as the research using the inoculum have given researchers the insight to characterize Pioneer®brand hybrids for resistance to this disease."
Heuchelin says Goss's wilt can cause significant yield loss on some hybrids, but Pioneer hybrids typically show good resistance to the disease. Goss's wilt tends to be more of a problem in cornfields that incurred plant damage, especially in corn-on-corn and minimum or no-till fields.
Goss's wilt limits yield by reducing green leaf area and causing premature death in corn plants. Timing of the infection has a critical role in the disease's influence on grain yield. Early infections lead to the greatest yield reductions - up to 50 percent yield loss when susceptible hybrids are infected early in the growing season. Other agronomic issues such as stalk lodging may result from fields that have died prematurely from Goss's wilt, resulting in further yield loss and lower quality grain.
"Once established in an area, it can surface in any given year depending on the environment," Heuchelin says. "The bacteria are spread by strong winds and also by equipment moving from field to field. Once reported in a field, it's considered to be part of the soil microbial environment for any fields in the surrounding area. Growers need to be aware of any reports in their area when they are selecting hybrids for next year and look for resistance ratings."
Carrying with it the potential of late-season problems in fields hit earlier by severe weather, Goss's wilt is moving into the Midwest from its long-established concentration in the Great Plains.
"While widespread screening for Goss's wilt is not common at most seed companies, Pioneer has one of the most robust disease-screening programs in the industry," Heuchelin says. "We have many years of data from in-field screening to characterize, and recommend hybrids with strong resistance ratings."
"The Pioneer rating system is one through nine and is based on the degree of infection, with level one for hybrids that show more than 50 percent yield loss and nine for hybrids that have no lesions," Curran says. "Genetic diversity is extremely important, and Pioneer offers a wide genetic range of hybrids with very good to excellent resistance to Goss's wilt and with an expanded maturity range of 75 to 118 days."
Continued screening of genetic material, identification of sources of resistance using all available technologies, including molecular markers, and recombination into new, improved hybrids are all instrumental in prevailing against Goss's wilt.
For more information on managing Goss's wilt or selecting hybrids resistant to this disease, contact your local Pioneer sales professional.