Growers are urged to keep a watchful eye on Goss's wilt this year, especially if they experienced light to heavy infections in 2011, say experts at Pioneer Hi-Bred, a DuPont business.
"Goss's wilt has a long history of wreaking havoc in cornfields in the western Corn Belt but continues to expand its boundaries north and eastward," says Scott Heuchelin, Pioneer research scientist, field pathology.
This yield-robbing disease is most common following violent weather such as straight-line winds, sandblasting and hailstorms. The residue-borne bacteria enter the plant's wounds, primarily through splashing of rain or irrigation water. If hybrids are highly susceptible to Goss's wilt, the disease most likely will appear the following week.
According to agronomists and researchers, Goss's wilt is spreading as far north as Canada and east across the Midwest into Indiana. It is crucial for growers to identify the disease, because once the bacterium infects the field, it may persist year after year.
Unfortunately, if Goss's wilt is indeed present, there is no chemical cure. Instead, growers are urged to minimize their risk by selecting resistance hybrids in the coming planting seasons.
Signs and Symptoms
Heuchelin says this disease can be very destructive - causing significant leaf loss, lower stalk quality and reduced yields. "As a result, growers should learn to identify the disease correctly to prevent recurring disease issues in future years."
It's easy to confuse Goss's wilt with environmental conditions such as drought stress or sun scald, as well as other leaf blights or nutrient deficiencies. Heuchelin recommends growers carefully examine their corn crops to make a proper diagnosis.
The first step is to scout fields to spot some of the distinguishing characteristics of Goss's wilt.
Since infection of corn can occur at any growth stage, it is important to inspect fields during early to midseason growth. There are two phases of the disease - systemic wilt phase and later-season foliar blight.
In the seedling stage, early infection can be systemic and result in:
- Discolored vascular tissue, with slimy stalk rot
- Buildup of bacteria in the vascular bundles, inhibiting the plant's ability to transfer water
- Stunted growth where the plant eventually wilts and dies as if drought stressed
Midseason Signs And Symptoms Include:
- Distinct dark green to black 'freckles' within or just outside of leaf lesions
- Shiny or glistening patches of dried bacterial ooze on the lesions - similar to a thin layer of varnish
- Water-soaked streaks, along with tan to gray lesions that run lengthwise on the leaves.
Fields most at risk for infection include those with continuous corn, grassy weeds, surface crop residue, minimum or no-till practices, and those planted with susceptible hybrids or with a history of Goss's wilt problems in the area.
These conditions increase the likelihood of Goss's wilt because they may harbor previously infected material or hosts for the bacteria. Additionally, heavy rainfall followed by hot, humid conditions favors rapid development of this disease after the initial infection.
Heuchelin says in-season management options of the disease are very limited.
"Goss's wilt is a bacterium; therefore it cannot be controlled by a fungicide. Instead, the best strategy is prevention in the off-season with genetic resistance," says Heuchelin. "Choosing a hybrid with high levels of Goss's wilt tolerance is the best line of defense - especially if the field has a history of previous infection."
Pioneer has conducted decades of research breeding for Goss's wilt resistance in the western Corn Belt and has developed highly resistant germplasm for deployment in environments with high Goss's wilt pressure. For the past several years, the company has introduced resistant traits into corn hybrids developed for the eastern areas of the Corn Belt.
Other tips to help avoid spread of the disease include managing the debris, which is the source of the inoculum, by working in rotation and tillage along with cleaning the equipment of crop residue before moving to other fields.