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Pierce’s Disease Found on Kentucky Grapevine
By
Aimee Nielson
 LEXINGTON,
Ky., (Sept. 12, 2007) – Extension specialists at the University
of Kentucky College of Agriculture have identified Pierce’s
Disease on a Vidal Blanc grapevine at the university’s
Horticulture Research Farm in Fayette County.
UK Viticulturalist Kaan Kurtural said laboratory tests on two
different samples were both positive and the affected plant has
been removed.
Pierce’s Disease is a deadly grapevine disease spread by certain
types of leafhoppers known as sharpshooters. Symptoms include
distinct reddish-brown scorching of leaf margins, with the part
of the leaf blade nearest the petiole remaining green.
“Other symptoms can include separation of leaf blades from
petioles, with petioles remaining on the vine, and alternate
green and brown banding along the affected grapevine,” said John
Hartman, UK plant pathologist. “Pierce’s Disease is caused by a
bacterium called Xylella fastidiosa. The disease can spread from
vine to vine in a vineyard, so it’s important to remove affected
vines.”
Some Kentuckians may be familiar with X. fastidiosa as a cause
of bacterial leaf scorch, a disease causing decline and death of
oaks and other landscape trees throughout the state. Although
the symptoms are similar and both diseases are fatal, bacterial
leaf scorch is caused by a different strain of X. fastidiosa
than the strain that causes Pierce’s Disease.
Hartman said recently a case of Pierce’s Disease was suspected
in Nelson County, but follow-up sample collection and extensive
laboratory testing could not verify the disease there. Leaf
scorching symptoms observed in that case may have been due to
lack of water due to drought, he said. Drought-scorched leaf
margins tend to take on a tan color rather than reddish brown.
Pierce’s Disease has been found in various grape-growing states
throughout the United States. According to a report by the
University of California at Davis, climatic differences between
regions can affect the timing and severity of symptoms, but not
the type of symptoms. Hot climates and areas experiencing severe
drought accelerate symptoms because moisture stress is more
severe even with adequate soil moisture.
The report went further to state that vines of susceptible
varieties deteriorate rapidly after appearance of symptoms.
Shoot growth of infected plants becomes progressively weaker as
symptoms become more pronounced.
“If you suspect you have a vine infected by Pierce’s Disease,
collect and deliver the sample to your county Cooperative
Extension Service office,” Hartman said. “The agent can submit
the samples to our lab for testing.” |
Contact: John Hartman, 859-257-7445, ext. 80720
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The UK College
of Agriculture, through its land-grant mission, reaches across
the commonwealth with teaching, research and extension
to enhance the lives of Kentuckians. |
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