Corn Bacterial Diseases

Amy Timmerman, Extension Educator Author

06/06/2024 Added

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Severe weather over the past two to four weeks has caused excessive damage to emerging and emerged crops. For the corn plants that were emerging during these events, they are at higher risk of potentially developing bacterial and fungal diseases due to the wounding on the leaves created by wind and hail. Goss’s Bacterial Wilt and Blight is one bacterial disease to be on the lookout for.

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[00:00:00.569]This Amy Timmerman with Nebraska Extension and today’s Extension update.
[00:00:05.896]Severe weather over the past two to four weeks has caused
[00:00:08.879]excessive damage to emerging and emerged crops.
[00:00:12.689]For the corn plants that were emerging during these events,
[00:00:15.459]they are at higher risk of potentially developing bacterial and fungal diseases
[00:00:20.419]due to the wounding on the leaves created by wind and hail.
[00:00:24.572]Goss’s Bacterial Wilt and Blight is one bacterial disease to be on the lookout for.
[00:00:30.348]The foliar stage of this disease has two major characteristics that
[00:00:34.748]can be used to distinguish it from other diseases.
[00:00:37.445]The first identifiable characteristic is the development of dark green to
[00:00:42.625]black discontinuous water-soaked spots, sometimes called "freckles"
[00:00:47.525]because of their appearance, near the edges of expanding lesions.
[00:00:51.555]The bacteria can also create an exudate or ‘ooze' on the
[00:00:55.505]surfaces of the leaf which is the second identifiable characteristic.
[00:00:59.813]When dried the exudate may glisten
[00:01:02.243]and appear shiny on the leaf surface similar to varnish.
[00:01:06.073]The wilt phase of the disease is not commonly seen but
[00:01:09.699]when infection occurs early in the season the probability increases.
[00:01:13.479]In the wilt phase, this occurs when the bacteria infect
[00:01:17.269]the vascular system and move within the plant.
[00:01:20.119]Infection may cause discoloration of the water-conducting elements
[00:01:24.119]and eventually a slimy stalk rot that can lead to wilting and plant death.
[00:01:29.801]Another bacterial disease that may be seen is bacterial leaf streak.
[00:01:34.096]This bacterial disease can infect the plant through natural openings in leaves,
[00:01:38.586]but wind-driven rain can also allow bacteria entry into the plant tissue.
[00:01:43.654]As temperatures increase, it is believed that the symptoms are exacerbated also.
[00:01:50.184]Symptoms of bacterial leaf streak look very similar to other common diseases,
[00:01:54.184]sometimes causing confusion and misdiagnoses especially early in the season.
[00:01:59.848]Narrow stripes between leaf veins may initially look like a common fungal disease
[00:02:03.848]gray leaf spot which is now being identified for the first time this year.
[00:02:09.854]Lesions usually have slightly wavy edges in contract to the
[00:02:13.942]smooth, linear lesions margins of gray leaf spot.
[00:02:18.052]When backlighting the leaves, the lesions will have a yellow
[00:02:21.122]“glow” or appearance to them which helps in identification.
[00:02:26.039]Finally, common smut which is a fungal disease
[00:02:29.673]as a high probability of having higher incidence this year.
[00:02:34.107]Common smut has also been called boil smut due to the development of galls.
[00:02:40.008]Following injury, spores germinated and infect plant tissue to cause the
[00:02:44.693]formation of galls on any plant part including leaves and stalks.
[00:02:49.947]Galls on stalks tend to be larger than those produced on infected leaves.
[00:02:55.030]As the gall matures, large amounts of black spores are produced.
[00:02:59.030]Galls found on stalks have been known to impact overall standability
[00:03:03.030]of the plant thus identification is important now to allow monitoring
[00:03:07.820]those fields later in the growing season, especially as we approach harvest.
[00:03:13.934]For all the diseases discussed today, management options are very limited.
[00:03:18.654]Reviewing seed catalogs on the varieties tolerance or resistance
[00:03:22.504]to Goss’s Bacterial Wilt and Blight and/or Bacterial leaf streak are important.
[00:03:29.305]If replanting is required for portions of fields, try to select varieties
[00:03:33.421]with high tolerance or resistance to Goss’s Wilt in particular with
[00:03:37.350]the weather patterns we have been experiencing so far.
[00:03:40.625]For fields that are showing symptoms,
[00:03:42.725]there is not pesticide treatment option available.
[00:03:45.975]Continue monitoring of these fields for disease progression is important
[00:03:49.975]throughout the remainder of the growing season because these plants
[00:03:53.524]will also be stressed and more susceptible to other diseases as the season progresses.
[00:03:58.980]If you need assistance with disease identification,
[00:04:01.910]samples can be sent into the Plant and Pest
[00:04:04.980]Diagnostic Clinic located on UNL's East Campus.
[00:04:07.610]Or reach out to your local extension educator or Dr. Tamra Jackson-Ziems
[00:04:12.610]who is the Extension Specialist focusing on corn diseases.
[00:04:16.060]This has been Amy Timmerman with Nebraska Extension.

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Corn Bacterial Diseases

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