Goss's Wilt, a tenacious bacterial disease of corn identified by its linear lesions and overall glossy appearance, reared its ugly head for many growers throughout the Upper Midwest this year.
Once thought to be a disease that only affected western states, the number of reported outbreaks has increased significantly in states throughout the Corn Belt, including Iowa, Nebraska, Wisconsin and Illinois. With the potential to cause significant yield damage, it is important for growers to be aware of the best ways to identify Goss's Wilt and manage against future outbreaks.
John Toft, regional sales manager for Latham Hi-Tech Seeds and a Certified Crop Advisor in Iowa and Nebraska, has seen a dramatic increase in the number of Goss's Wilt cases this year. Toft, who earned a bachelor's degree in Agronomy and Agribusiness Management before earning his graduate degree at Iowa State University in Seed Technology and Plant Diseases, says continuous corn production, minimal tillage practices and severe weather conditions all contributed to the appearance of Goss's Wilt in 2011.
Why was Goss's Wilt so widespread during 2011 growing season?
"All the storm damage this year, including hail and straight-line winds, played a significant role in the spike of Goss's Wilt," says Toft. "Stalk bruising and leaf shredding provide ways for pathogens to enter the corn plant. High night-time temperatures, which many areas also experienced, favor the spread of Goss' Wilt, as well."
Identification is the first step in learning how to combat any disease, and since Goss's Wilt can be easily mistaken for Gray Leaf Spot, it is important to recognize its unique symptoms, says Toft.
Goss's Wilt can be identified by light tan-to-gray lesions, with wavy or irregular margins that follow leaf veins. Within these lesions, it is common to find dark green to black specks. The lesions often have a shiny appearance, due to the byproduct the bacteria secretes; this waxy appearance is a key identifier and differentiates the disease from imitators, like Gray Leaf Spot.
Corn growers need to take preventative steps to avoid Goss's Wilt
When Goss's Wilt is identified within a field, Toft says in-season management options are extremely limited for growers. "Oftentimes, growers spray foliar fungicide believing they're fighting diseases like Goss's Wilt," he notes. "However, since Goss's is a bacterial disease, fungicides have no effect."
Due to limited treatment options, it's important for growers to initiate preventative steps during the off-season to avoid significant yield loss the following year. To avoid Goss's Wilt in 2012, farmers should keep recommended management practices in mind, which include growing resistant corn hybrids, rotating crops and managing crop residue.
* Resistant corn hybrids. Seed selection will play an even more important role as Goss's Wilt becomes more prevalent, and one of the best ways to protect against Goss's Wilt is through proper hybrid selection.
If a grower had Goss's in 2011, it's important for them to select a highly resistant hybrid if returning to corn once again in 2012 in that same field. Toft recommends growers contact their local seed dealer to help them identify hybrids that show genetic resistance to Goss's Wilt.
* Crop rotation. Goss's Wilt has the ability to overwinter in the previous year's crop residue, allowing the disease to easily re-infest corn crops the following year. To avoid reoccurrence of Goss's Wilt, Toft recommends crop rotation as a preventative measure.
"Fields with continuous corn-on-corn provide the perfect environment for diseases like Goss's Wilt," he says. "It makes it easier for the disease to develop quickly and doesn't give the crop a chance to die off."
* Crop residue management. Proper tillage is extremely important to combat Goss's Wilt. Some tillage methods, including no-till, don't properly break down residue, preventing the disease from being destroyed.
"If a field experienced Goss's in 2011, aggressive tillage practices will help suppress susceptibility for the coming year," says Toft. "But there are soil conservation concerns to keep in mind too."
Summing up, Toft makes these three key points:
* Follow these tips to protect fields against the growing threat of Goss's Wilt.
* Choosing corn hybrids having strong resistance is your first line of defense.
* Crop rotation and crop residue management are other practices that can help.