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 In 2016, corn producers in Nebraska noted a new type of damage to
corn leaves. Research done at that time indicated that while the
symptoms presented appeared to resemble the fungal disease Gray Leaf
Spot, there were marked differences that brought Nebraska scientists
to conclude they were dealing with a new dilemma.
In 2016, the disease spread throughout the Cornbelt, and was finally
in August of last year noted in one Illinois county to the north.
Dekalb was one of 68 counties where field surveys were conducted.
Out of more than 300 fields sampled, the disease appeared in only
one.
However, Illinois agronomists are looking for the disease to repeat
itself and spread throughout the area in the coming years.
Currently, there is not enough scientific data to know what impact
the disease will have on yields. Time will tell as research
continues. It also appears that current disease resistant hybrids
are not immune to this new illness. Though it has been noted in
other states that some hybrids appear to fair better than others, no
one has staked a claim on having a product that is truly resistant
to Bacterial Leaf Streak. However, agronomists believe that the
eventual best practice may be to select the most resistant hybrids,
when that information is made available.
 Scientists have made progress in tracking the disease and
determining the factors that may contribute to the disease. Most
believe that the disease has come to the United States from corn
grown in South Africa, but there are also indicators that the
disease may have originated in Sugar Cane.
Fields that are most susceptible to getting the disease are those
with pivot sprinkler irrigation, and also fields where no-till
practices are used.
Spread of the disease from field to field appears to be through high
wind and rain, and the disease appears to grow quicker during hot
humid conditions.
According to an article written by N. Dennis Bowman and Suzanne
Bissonnette of the University of Illinois “The disease causes the
formation of linear lesions between the veins on a corn leaf. The
lesions look similar to gray leaf spot (GLS) symptoms. GLS lesions
tend to be shorter, more rectangular and stay within their veinal
borders. However in contrast, Bacterial Leaf Streak lesions are more
irregular, often thinner and longer, will “bleed” over the veinal
border and may have a halo when held up to the light. “In many Great Plains states that have found the disease, symptoms
first appear on the lower leaves and infection progresses up the
plant. Typically these fields have been under pivot irrigation.
However later infections may occur and show up primarily in the
upper canopy, as was the case for the positive DeKalb county
sample.”
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Because the disease bears a close resemblance to the fungal disease
Gray Leaf Spot, it will be important for producers to identify the
disease before spending money to eradicate it. Fungal treatments
used for Gray Leaf Spot will not be effective on Bacterial Leaf
Streak, so treatment would be dollars wasted at this time.
Currently, there is no treatment for Bacterial Leaf streak, so the
next best practice is going to be to work toward preventing the
spread of the disease to other fields or farms.
Researchers at the University of Nebraska are making the following
suggestions. “Sanitation practices such as cleaning debris from
combines and other equipment between fields can help slow its spread
to unaffected fields.
“In some cropping systems use of crop rotation or tillage may help
degrade infected corn debris and reduce the surviving bacteria.
“However, neither practice will eradicate the bacterium and
eliminate the risk of disease.”
Finally, because the disease is relatively new, there has been
insufficient information gathered to determine how the disease will
impact yields.
If you suspect Bacterial Leaf streak, is present in your fields, the
University of Illinois wants to know. Submit a sample to the
University of Illinois Plant Clinic, S-417 Turner Hall, 1102 S.
Goodwin Ave., Urbana, IL 61801, Phone: 217-333-0519, Email:
plantclinic@illinois.edu
Sources:
Find pictorial information about
Bacterial Leaf Streak and other corn leaf disorders at this website:
Crop Protection Network -
http://cropprotectionnetwork.org/corn/cpn-2008-bacterial-leaf-streak/
University of Illinois “The Bulletin”
August 26, 2016
http://bulletin.ipm.illinois.edu/?p=3716
University of Nebraska-Lincoln Cropwatch – February 23, 2017
Resource:
http://cropwatch.unl.edu/2017/update-bacterial-leaf-streak-corn-nebraska
Successful Farming – September 2, 2016
Resource:
http://www.agriculture.com/crops/bacterial-leaf-streak-is-a-new-corn-disease
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