The Purdue Plant and Pest Diagnostic Laboratory

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August 11, 2008

Goss’s Bacterial Wilt and Leaf Blight on Corn

Kiersten Wise and Gail Ruhl, Department of Botany & Plant Pathology, Purdue University

First confirmed report in Indiana

There is a new disease of corn on the scene in Indiana—Goss’s Wilt. The disease was confirmed at the Purdue Plant and Pest Diagnostic Laboratory this week on field corn and popcorn samples submitted from northern Indiana. Goss’s Wilt is a bacterial disease that infects susceptible varieties of sweet corn, popcorn, and hybrid corn. This is Purdue’s first confirmation of Goss’s Wilt in Indiana since the disease was discovered on corn in Nebraska in 1969 (1). The disease is found sporadically throughout the Midwest in limited areas and years, and is currently only present in one county in Indiana.

Goss’s Wilt is caused by the Gram positive bacterium Clavibacter michiganensis subsp. nebraskensis and is characterized by distinct light tan to gray lesions filled with dark specks (Figure 1). Lesions will often appear shiny due to bacteria oozing onto the leaf surface (Figure 2). Blighted areas are common in susceptible varieties (Figure 3), and can be confused with sunscald or drought stress. The dark flecking and shiny areas within lesions distinguish Goss’s Wilt from another common bacterial disease known as Stewart’s Wilt and Leaf Blight (Figure 4). Stewart’s Wilt is caused by a Gram negative bacterium, Pantoea stewartii. Leaf blight symptoms of Stewart’s Wilt are elongated, run parallel to the veins and taper off to a point but do not exhibit the freckles of shiny, bacterial exudate observed on leaf lesions of plants infected by Goss’s Wilt. Both of these bacterial diseases can infect the vascular tissue of the plant causing a systemic infection. Infected vascular tissue in plants infected by Goss’s Wilt appears orange to brown and can cause wilting and stalk degradation.

The bacteria overwinter in infected residue on the soil or in limited weed hosts. Reducing the amount of debris remaining on the field through conventional or limited tillage practices is of primary importance. Rotation to soybean, wheat, alfalfa or another non-host can also help encourage decomposition of infected corn debris. Replanting corn into infected corn stubble is strongly discouraged in areas where the infection has occurred.

Studies in Nebraska have shown that the bacteria is capable of being both seedborne and seed transmitted. The disease is not insect-transmitted, like Stewart’s Wilt, and relies on wounds for dispersal. Once seed to seedling transmission occurs, disease spreads in areas that have experienced hail-damage or wind-driven rain. Early hailstorms and recent heavy rains and windstorms likely contributed to the infection and dispersal of Goss’s Wilt in fields in Indiana.

Currently, the susceptibility level of most varieties of popcorn, sweet corn, and hybrid corn to Goss’s Wilt in Indiana is unknown. Partially resistant hybrids are available in other areas of the Midwest, such as Nebraska, but hybrid performance in Indiana is unknown at this time. It is important to note that fungicides will NOT have an impact on Goss’s Wilt, since the disease is caused by a bacteria and not a fungus.

Other plant diseases or injuries can easily be mistaken for Goss’s Wilt. Suspect samples may be sent to the Purdue Plant and Pest Diagnostic Lab for diagnosis. There is an $11.00 sample handling fee and an additional $25.00 testing fee for serological confirmation of the bacteria.


For more information on Goss's Wilt, check out the following publications:

Purdue Publication BP-81: Goss's Bacterial Wilt and Leaf Blight (pdf file)

University of Nebraska Extension Bulletin on the disease (pdf file).

 

Click image to enlarge

Goss wilt on corn

Figure 1. Diagnostic lesions of Goss’s wilt with dark specks or ‘freckles’ present in the lesion.

Goss wilt on corn

Figure 2. Bacterial ooze present on the lesion surface will appear shiny in sunlight.

Goss wilt on corn field

Figure 3. Blighted areas in the upper canopy of infected plants.

Goss wilt on corn

Figure 4. Stewart's bacterial wilt and leaf blight

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service