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.
in Nebraska have shown that the bacteria is capable of being both
seedborne and seed transmitted. The disease is not insect-transmitted,
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)
of Nebraska Extension Bulletin on the disease (pdf file).
Click image to enlarge
Figure 1. Diagnostic lesions of Goss’s
wilt with dark specks or ‘freckles’ present in the
Figure 2. Bacterial ooze present on the lesion
surface will appear shiny in sunlight.
Figure 3. Blighted areas in the upper canopy
of infected plants.
Figure 4. Stewart's bacterial wilt and leaf blight