A ProMED-mail post
<http://www.promedmail.org>
ProMED-mail is a program of the International Society for Infectious Diseases <http://www.isid.org>

Date: 12 Jul 2009
Source: The Grant Tribune Sentinel [edited]
<http://www.granttribune.com/index.php?option=com_content&view=article&id=1210:gosss-wilt-showing-up-in-perkins-county-crops&catid=35:ag-news&Itemid=55>

Goss's bacterial wilt and blight has been confirmed by the UNL [University of Nebraska-Lincoln] in samples received from southwest Nebraska, with more unconfirmed reports in eastern Nebraska. Last year [2008] was the 1st time the disease was confirmed statewide in approximately 2 decades. The recent re-emergence of the disease indicates an increased risk this year [2009] because of the abundance of bacterial inoculum to have overwintered. In addition, the recent severe weather that damaged corn crops is also likely to contribute to [the] disease.

Bacterial stalk rot was identified in corn and sorghum in Seward County [southeast Nebraska], with several other unconfirmed reports in south central and southeast Nebraska. This disease may be caused by one of several common bacterial pathogens that occur in the soil and can overwinter in crop residue. The disease is often favored by high temperatures and humidity and also develops in fields that have been exposed to flooding, which is consistent with recent weather events in areas of Nebraska.

Holcus spot continues to appear in Nebraska fields. It can appear like diseases caused by fungi, such as eyespot and gray leaf spot.

Unfortunately, rescue treatments are not currently available for any of these diseases. Because all of them are caused by bacteria, control with foliar fungicides is not expected [to work].

--
Communicated by:
ProMED-mail
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[Goss's wilt and blight of maize is caused by the bacterium _Clavibacter michiganensis_ subsp. _nebraskensis_. It is a persistent and economically serious disease of susceptible maize hybrids in the USA. The bacterium can also affect some grasses, which may serve as pathogen reservoirs. Symptoms include systemic wilting and/or leaf lesions and blighting. Infection of leaves, stems, and roots occurs primarily through wounds (mechanical, hail, or insect damage), and plants are susceptible at all growth stages. The pathogen is seed transmitted and overwinters on crop debris and maize kernels. Subsp. _nebraskensis_ has so far not been reported outside the USA, however other subspecies found elsewhere include _sepedonicus_ (potato ring rot) and _michiganensis_ (bacterial canker of tomatoes) which cause severe yield losses on their respective hosts.

Bacterial stalk rot of maize is caused by _Pectobacterium chrysanthemi_ pathovar _zeae_ (synonym _Erwinia carotovora_ f. sp. _zeae_) and possibly related species. The pathogen can also affect millets of the genera _Sorghum_ and _Pennisetum_ and can cause soft rot in a wide range of vegetable and other crops.

Holcus spot of maize is caused by the bacterium _Pseudomonas syringae_ pv. _syringae_ which is a common epiphyte on both leaves and seeds of many plants. This pathogen also causes diseases of, for example, tomato, citrus, mango, and apricot, and seed transmission is suspected in some hosts. Other pathovars also exist which can affect different hosts.

Disease management of bacterial diseases may include cultural practices to minimise inoculum, crop rotation, phytosanitation to prevent spread, and use of resistant crop varieties.

The fungal diseases of maize mentioned above are eyespot caused by _Kabatiella zeae_ and grey leaf spot caused by _Cercospora zeae-maydis_. For more information on these see previous ProMED-mail posts in the archives.

Maps
USA:
<http://www.mapsofworld.com/usa/usa-road-map-enlarge-view.html>,
<http://www.mapsofworld.com/usa/usa-state-and-capital-map.html>  and
<http://healthmap.org/promed?v=40,-97.6,4>
Nebraska:
<http://www.lib.utexas.edu/maps/united_states/nebraska_1990.jpg>

Pictures of symptoms on maize
Goss's wilt symptoms:
<http://cropwatch.unl.edu/photos/cwphoto/crop06-19gosswilt.jpg>,
<http://elkhorn.unl.edu/epublic/live/g1675/build/graphics/g1675-3.jpg>,
<http://elkhorn.unl.edu/epublic/live/g1675/build/graphics/g1675-5.jpg>,  and via <http://www.ipmimages.org/browse/subimages.cfm?area=72⊂=20561>
Bacterial stalk rot:
<http://pdc.unl.edu/image/image_gallery?img_id=29442&t=1199743971721>
Holcus spot:
<http://www.lgseeds.com/lg_tech2/images/holcusspot.gif>

Links
Information on Goss's wilt:
<http://www.ianrpubs.unl.edu/epublic/pages/publicationD.jsp?publicationId=679>,
<http://www.ianrpubs.unl.edu/epublic/live/g1675/build/g1675.pdf>,
<http://www.lgseeds.com/LG_Tech2/Goss%20Wilt.asp>,  and <http://cropwatch.unl.edu/archives/2006/Crop19/gosswilt.htm>
Information on bacterial stalk rot of maize and sorghum:
<http://pdc.unl.edu/agriculturecrops/corn/bacterialstalkrot>,
<http://cropdisease.cropsci.illinois.edu/corn/Bacterialstalkrot.html>
and
<http://www.ncbi.nlm.nih.gov/pubmed/857508>
Information on holcus spot of maize:
<http://www.lgseeds.com/lg_tech2/holcusspot.asp>
Taxonomy of all bacterial pathogens via:
<http://www.bacterio.cict.fr/search.html>
List of diseases and pathogens of maize:
<http://www.apsnet.org/online/common/names/corn.asp>
- Mod.DHA]