Stewart's disease (bacterial wilt)
Stewart's disease (bacterial wilt)
Stewart's disease is caused by the bacterium Erwinia stewartii (Smith)
Dye. The bacterium is transmitted by several insects but the
corn flea beetle (Chaetocnema pulicaria Melsh.)
is considered the most important in the life cycle of the pathogen.
Flea beetles overwinter as adults and the bacterium survives
between crops in the insect. The pathogen is transmitted to the
new crop when flea beetles begin feeding. warm winter temperatures
result in a high survival rate of insects and a higher incidence
of Stewart's wilt in the spring. The bacterium can also survive in seed but
this type of transmission is considered most important in carrying
the disease to new areas rather than as a source of primary inoculum
in areas with a history of Stewart's
wilt. Secondary infection occurs when insect vectors transfer
the bacterium (through feeding) to healthy plants. Corn, eastern
gamagrass and teosinte naturally infected hosts of E. stewartii.
With few exceptions, sweet corn is more susceptible than dent
corn. The bacterium has also been successfully artificially
inoculated on sorghum, Sudangrass and a number of weeds commonly
found in Nebraska. Host susceptibility is influences by mineral
availability. Susceptibility is increased by high levels of ammonium
N and phosphorous and decreased by high levels of potassium and
calcium. Disease severity is also increased by high temperatures.
Symptoms
Susceptible hosts may be infected at any stage
of growth development and a wide range of symptoms are associated
with this disease. Plants infected as seedlings wither and die.
Plants infected early that don't
die are stunted, have abnormal ears and bleached or dead tassels.
When infection occurs after tasseling, distinct leaf lesions
develop. Watersoaked streaks are formed parallel to the vein.
The streaks are light green to yellow with a wavy, irregular
margin. They turn tan , enlarge and coalesce with age; resulting
in blighting or "firing
of leaves. Insect feeding scars can be observed in these lesions
when they are held up to the light. Secondary spread of the pathogen
also occurs via the leaf lesions. Severely infected plants have
discolored cavities in the pith near the soil line. The bacteria
spread through the vascular system and may enter the kernels.
When stalks or leaves of these plants are cut open droplets of
yellow bacterial ooze extrude from vascular tissue.
Plant Health Management
Resistant Hybrids
Plant material exhibiting
good resistance is available for both dent and sweet corn and
is most important to the sweet corn industry.
Flea beetle control.
Effective control of the corn flea beetle reduces the incidence of the disease, particularly
primary infections.
Clean Seed?
Do not used seed produced in a field contaminated by Stewart's
wilt.
References
McGee, D.C., 1994. Maize Diseases, A reference source for seed technologists.
American Phytopathological Society. St. Paul, MN, pp.36-39.
Nyvall,R.F. 1989. Field Crop Diseases Handbook (2nd. ed.).
American Phytopathological Society, St. Paul, MN, pp. 95-96.
Pepper,E.H.1967. Stewart's Bacterial Wilt of Corn.
Monograph 4, American Phytopathological Society, St. Paul, MN.
Schurtleff, M.C. (ed.), Compendium of Corn Diseases (2nd. ed.).
American Phytopathological Society, St. Paul, MN pp. 5-7.
Highlighted Area
Severe outbreaks of Stewart's ilt are sporadic but a widespread epidemic in the U.S.
and parts of Canada (Ontario) occurred in 1932.
Common name synonyms: Stewart's bacterial wilt; Stewart's wilt; Bacterial wilt; Bacterial wilt;
Stewart's leaf blight; Stewart's disease; Maize bacteriosis.
Scientific name synonyms: Pseudomonas stewartii;
Bacterium stewartii; Aplanobacter stewartii; Bacillus
stewartii; Phytomonas stewartii; Xanthomonas stewartii.
Insects vectors associated with secondary spread
of Stewart's
wilt: corn flea beetle (Chaetocnema pulicaria), toothed
flea beetle (C. denticulata), 12-spotted cucumber beetle
(larval stage aka Souther corn rootworm)(Diabrotica undecimpunctata
howardi, Northern corn rootworm (D. logicornis),
Western corn rootworm (D. virgifera), May beetles (larval
or white grub stage)(Phyllophage sp.), Seed corn maggot
larvae (Hylemya cilicrura), common wheat wireworm (and
adult stage) (Agriotes mancus).
From the Iowa State Link Site:
The system used to predict survival of the insect
and risk of the disease is based on winter temperatures. An index is calculated by simply adding the mean monthly temperatures for December, January, and February. When
the average temperature for these three months added together exceeds 90° F, environmental conditions favor survival of flea beetles and the risk of Stewart's disease is high.
Stevens-Boewe Index for prediction of Stewart's disease.
Index |
Level of Severity |
| 90 and above |
Severe |
| 85 - 90 |
Moderate to Severe |
| 80 - 85 |
Light to Moderate |
| Less that 80 |
Trace |
Useful Links
Caveat
This description is presented for information only and no endorsement is intented for
products listed, nor criticism meant for products not mentioned. Always consult the product
label before bying and using any fungicide.
Material contained on the Links from the page are the responsibility of the linked page's author(s).
Questions, Comments, Complaints and Complements?
This page was drafted by:
Jane Christensen,
Department of Plant Pathology, University of Nebraska-Lincoln
Disease images were provided given by:
Dr. David Wysong,
Department of Plant Pathology, University of Nebraska-Lincoln
This page is maintained by:
Dr. J.E. Partridge, Department of Plant Pathology, University of Nebraska-Lincoln
jpartridge1@unl.edu
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Copyright (C) 2003 J.E. Partridge, University of Nebraska-Lincoln. All Rights Reserved.
