 Backyard Farming in the River Valley Podcast
May 8, 2009
Fire Blight (3:30 minutes)
Audio/Video Script:
Dustin Blakey
County Extension Agent - Agriculture[Title slide - River Valley Gardening,
Fire Blight, Dustin Blakey County Extension Agent for the University of Arkansas
Division of Agriculture]
[Dustin Blakey] Early this week I was taking the trash out to the street when
I noticed that the ugly pear tree in front of my house had seemingly turned
black overnight.
What happened? Well, my tree has a disease called fire blight.
Hi, this is Dustin Blakey, County Extension Agent with the University of
Arkansas Division of Agriculture and we’re going to talk about fire blight.
[Pictures showing fire blight] Fire blight is a serious disease that affects
pears, apples, quince, and a few other trees and shrubs in the Rose Family. Fire
blight is an aptly named disease. Its symptoms look like parts of the plant have
been burnt by some mysterious process. Maybe tiny fairies armed with
flame-throwing magic wands? [Drawing of a fairy shooting flames onto a tree]
Unfortunately, it’s nothing that exciting.
[Picture of Cedar-Apple Rust (fungus) on a tree] Fruit trees and their
ornamental relatives, as you know, are subject to getting several diseases.
[Picture of Apple Scab (fungus) ] For the most part they are caused by fungi,
[picture of Brown Rot (fungus) on a tree] but a few are caused by bacterial
infections, [picture of fire blight (bacterium) on pear fruit] and this includes
fire blight. The particular bacterium that causes fire blight is called
Erwinia amylovora. [Picture of a micrograph of Erwinia amylovora
bacteria]
Fire blight infections usually begin during the bloom period. Bees and flies
are attracted to the blossoms and spread the bacteria from other plants.
[Drawing showing two trees and how the infection spreads, insects, old
infections, rain and wind] [Picture of a tree with Fire Blight] Since the flower
tissue is very delicate it serves as an easy infection point. Temperatures in
the mid-60s to upper-70s encourage the bacteria to multiply, which kills the
infected tissue.
The first symptoms of the disease are wilting blossoms and shoots. [Picture
showing wilted shoots] When the temperature increases entire branches will turn
black and wilted. This symptom is characteristic of fire blight and even gets a
special name: a shepherd’s crook. [Picture showing black and wilted branches -
shepherd's crook]
Depending on the susceptibility of the host plant, fire blight can spread and
kill the entire tree. [Picture of an entire orchard with Fire Blight] Sometimes
the infection is so ugly, even if it doesn’t kill the tree, you wish it would.
[Picture of branch with Fire Blight]
[Dustin Blakey] Fire blight is very difficult to control. This best thing of
all is to plant resistant varieties. Sorry: that means you can’t plant Bartlett
pears or Gala apples. Your County Extension Office has a list of resistant fruit
tree varieties that you can plant. You can also find that online. [Google: "FSA-6129"]
[Picture of someone pruning trees in an orchard] If you have fire blight in
your tree, it is important to prune it out as soon as you notice it. [Picture of
a limb with both diseased and healthy areas] Pruning cuts need to be made 8 to
12" past the infection into healthy wood to be effective. If possible, clean
your pruners with bleach or alcohol between cuts to prevent further spread of
the disease. [Picture of a tree with limbs removed] If you fail to prune out all
of the diseased tissue it will rear its ugly head next spring, possibly killing
the entire tree.
[Picture of a severly pruned tree] Sometimes this severe pruning leaves very
little of the tree behind. If this is the case, you may want to remove the tree
entirely and plant something else. There are lots of alternatives to callery
pears for use in the landscape. The last thing Arkansas’ landscapes need is more
Bradford pears.
[Dustin Blakey] While it’s possible to spray antibiotics to help control fire
blight, homeowners usually don’t have the means or ambition to do it right. I’d
say the best thing is to be diligent about pruning out infections, and do
everything in your power to disourage vigorous spring growth. That means don’t
top your trees and don’t over-fertilize.
If you have any questions about fire blight or other fruit tree diseases,
contact your County Extension Office.
[Title slide] For more information contact your County Extension Office
dblakey@uaex.edu U of A University of
Arkansas Division of Agriculture Cooperative Extension Service.
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