Q. I planted a five-gallon pear tree about three springs
ago and it seems pretty happy espaliered along my west-facing block wall, but a
few new leaves on three of the branches have some kind of black rot on them. It
has rotted away part of the leaf on some of them. Can you tell me what this
disease is and whether and how to fight it?
but the pear did not have blossoms this spring.
planted nearby at the same time, and it seems unaffected.
to mind. First, last year was a pretty bad year for a disease that attacks
European pears, Asian pears and apples. This is a bacterial disease called
fireblight. What you are seeing now in spring 2014 may be a remnant of fireblight from the previous growing season (2013). It can be particularly bad on Asian pears.
 |
| Again in about May you see some of the new growth dying back from fireblight, dead leaves and upon close inspection the blackened growth. |
.JPG) |
| New succulent growth in May in our climate causes the blackening of the growth and the telltale hook or shepards hook commonly talked about with fireblight |
This disease can be devastating to these fruit trees. The disease
normally starts near where the flowers are produced. This disease can spread
down the limbs and in the case of Asian pears in our desert climate, the
disease can kill the tree. It normally does not do this to European pear or
apple here in our climate.
The disease turns these parts of the plant and even
some small limbs dark black, like they were scorched with fire, hence the name.
A telltale sign is distorted young growth in that area that is bent backwards
into a hook.
If this is the case or you suspect it might be then cut out this
diseased portion 12 inches below the infection. Sterilize the pruning shears or
saw with a strong disinfectant such as alcohol or Lysol. Do that between each
cut on that particular tree to prevent reinfecting it.
I pay particular attention to the weather during bloom time (that is happening now in apples and pears in our climate). If it is rainy and windy I can usually expect problems from fireblight. That is exactly what happened this time last year.
The second thing is that
pear leaves normally turn black if they are injured in some way. That would be
a normal color for damaged or dying or dead pear leaves. So if it is just
affecting the leaves and they are black then I would not assume it to be
fireblight. But if it is in the branches then you need to cut out the infection
as I described.
Comment from Tom Spellman at Dave Wilson Nursery to me in an email…. He is talking about the disinfectant needed on pruning shears and saws when removing infected limbs and shoots.
Hey Bob, just a comment on the section where you mentioned Fire Blite. Studies have shown that the only reliable disinfectant for sterilization is a 50/50 mix of household bleach and water. Alcohol and other disinfectants have proven to be almost useless.
Comment from Tom Spellman at Dave Wilson Nursery to me in an email…. He is talking about the disinfectant needed on pruning shears and saws when removing infected limbs and shoots.
Hey Bob, just a comment on the section where you mentioned Fire Blite. Studies have shown that the only reliable disinfectant for sterilization is a 50/50 mix of household bleach and water. Alcohol and other disinfectants have proven to be almost useless.