Goss's wilt, a corn disease that can rob yields and tends to show up more in no-till situations and in continuous corn, has arrived early in this 2011 growing season.
On June 24, Alison Robertson, an Iowa State University Extension plant pathologist, visited a grower's field in Carroll County in west central Iowa where ISU has a research study on Goss's wilt, a corn disease. The field has been in corn for several years and has a history of Goss's wilt. The field was planted May 5 and the corn was at growth stage V6 to V7 when the disease showed up.
"We found plants with typical symptoms of the leaf blight (See Figure 1) and also the wilting stage of the disease. This is the earliest report of Goss's wilt in Iowa that I am aware of. It is also the first time I have seen the wilting stage of the disease in this state," she says.
This week's "Crop Minute" features discussion of Goss's wilt
To listen to a short 2 minute report, click on http://agron.iastate.edu/cropminute. Robertson discusses the early occurrence of Goss's wilt and provides management tips. Also, read the rest of this article, as she offers the following explanation of what's happening and what to watch for in your corn this summer.
"Typical lesions of Goss' wilt were characteristic of approximately 1% of the plants in the field," says Robertson. Long, dark brown to grey-green lesions were evident on the edge of the leaves or along folds in the leaf. Freckles, which are diagnostic for Goss's, were present. On some plants, only one leaf was affected, while on other plants, all leaves were affected (See Figure 2).
"We also noticed some plants that were wilted," she says. "Closer examination of the plants revealed subtle lesions. When the stalk of the plant was cut, the vascular system of the plant was discolored orange-brown (Figure 3). In this case, infection of the plant by the bacterium was systemic. In other words, the bacterium was present in and plugging the vascular system of the plant."
There are no rescue treatments; how can you control Goss's wilt?
There are no rescue treatments for Goss's wilt. This disease is caused by the bacterium Clavibacter michiganenisis subsp. nebraskaenesis. So fungicides are not effective on it. Fungicides can control diseases that are caused by fungus, but not diseases that are caused by bacteria.
Management recommendations to control Goss's wilt include planting corn hybrids that have resistance to Goss's wilt, and rotating the field to a non-host crop. Also, you can use crop residue management to help control the disease but be careful how much crop residue you bury with tillage, because of the soil erosion potential.