By Dean Malvick, Department of Plant Pathology
The fact that Goss's wilt is was a widespread corn disease in Minnesota in 2011 is broadly known. The question of how much Goss's wilt will develop in 2012 is dependent in part on field and weather conditions. As of June 13, 2012, Goss's wilt had been confirmed over the previous week in several counties in Iowa and Nebraska. Thus it could also start to appear soon in Minnesota. This article summarizes key points about this disease, including where it has been confirmed in Minnesota, factors that favor its development, and how to recognize it.
Goss's wilt was first confirmed in Minnesota in 2009, and by the end of 2011 was found in many fields in over 30 counties across southern Minnesota and into the lower Red River Valley (as shown below). This disease caused only minor damage and minimal yield loss in most fields, however, yield loss was significant in some fields. The map below shows counties with confirmed Goss's wilt infections based on University of Minnesota testing, but this disease likely also occurred in other areas. Thus, there appears to be a risk for this disease across much of the Minnesota corn production area. Risk for individual fields, however, will likely vary from very low to higher based on environmental conditions and field history.
There is no complete
understanding of all the factors that lead to development of Goss's wilt in a
pathogen survives between crops in infected corn residue near the soil surface.
Goss's wilt may be more likely to develop where: fields are planted with hybrids
susceptible to Goss's wilt, in fields or areas where this disease has occurred in
the past two years, where much infected corn crop residue remains near the surface, in
fields that have been in continuous corn and have not been rotated, perhaps
where corn plant populations are high, and where leaves are injured by hail or strong
winds accompanied by blowing rain and sand/soil.
Goss's wilt can appear throughout the season, and was seen primarily in August in the past two years in Minnesota. It kills leaf tissue and also can infect stalks and kill entire plants. The leaf symptoms begin first as dark green water soaked areas with dark spots often called 'freckles'. These areas usually develop into large elongated tan lesions with irregular margins. Dark green spots ("freckles') and shiny patches of dried bacterial ooze that looks like dry egg-white develop in the lesions. Samples can be sent for diagnosis to the University of Minnesota Plant Disease Clinic (http://pdc.umn.edu/, 612-625-1275)
things to consider doing this season related to Goss's wilt are to learn how to
recognize this disease, scout fields and have appropriate diagnosis done to document
which fields have Goss's wilt, and check hybrids to determine how well they are
resisting development of Goss's wilt.
At this point there is minimal information available to suggest how effective
any foliar product is for managing Goss's wilt.
But if tempted to try a product, please leave untreated check strips in
fields so you can compare disease and yield levels to assess product efficacy.