Symptoms of Fireblight include browning/blackened leaves drooping in a classic 'shepherd's crook' |
To have an apple tree is to risk infection from this deadly
disease, one that includes oozing bacteria, curled, brown leaves, inedible
fruit, and spreading cankers. This year,
with several hail storms coming just as the tree was in bloom proved fatal. Temperatures and moisture played a role in
the infestation and my tree is entirely engulfed and without hope for recovery.
My tree isn’t alone.
In the past week, samples and emails have been brought to our office by
people in similar situations, conversations sound more like support groups, and
the disease is everywhere I look. My
mind cues up the dramatic, Hitchcockesque music each time I see another
blighted tree.
It’s a banner season for fireblight, a bacterial disease
that is especially destructive to apple, pear, quince and crabapple. It attacks
in spring, when temperatures reach 65 degrees F and frequent rain occurs. Bacteria overwintered in cankers on the tree
resume activity, multiplying rapidly. Hail drives the bacteria around and into woody
tissues.
Fireblight bacteria moving back into the twigs, blackening the wood |
Our wet early summer weather created good conditions for this
damaging disease, and masses of bacteria have been forced up through cracks and
bark pores to the bark surface, forming a sweet, gummy exudate called bacterial
ooze. Insects are pickingd up the bacteria on their bodies and carrying it to
opening blossoms where it infects trees.
Girdling cankers – areas of disease on the wood - eventually
develop from branch or blossom infections.
Leaves wilt, darken and curl to form a shepherd’s crook. This gives the
tree a fire-scorched appearance, thus the name "fire blight."
There is no cure for this disease, so prevention is the best
solution. Remove and destroy newly infected young twigs as soon as possible, so
that your tree doesn’t become the mother ship for disease in the neighborhood. Do this when no rain is predicted for at
least two weeks. It may be best to leave
pruning until winter when the bacteria are not active. In young twigs, make
cuts at least 12 inches below the dark, visible edge of infection to avoid
slicing into the bacteria. Remove all blighted twigs and cankered branches.
Prune larger limbs about 6 to 12 inches below the edge of visible infection.
After each cut, surface sterilize all tools used in pruning.
Spray tools with Lysol or dip tools in 70-percent ethyl alcohol, or a
10-percent bleach solution. Bleach can
rust tools, so if you use this to sterilize your pruners, wash them after
you’re done and apply a light tool oil to keep them rust-free.
Be on the lookout for apple scab, a fungus that attacks
leaves and fruit, which also favors cool, wet weather. You’ll seeing the rapid spread of this
disease across apples and crabapples. At
first, leaves get yellow or dark olive-colored spots, then turn yellow and fall
off. Fruit develops dark, greasy-looking
spots that then become sunken.
The disease overwinters on fallen leaves, so clean the area
during fall. Avoid overhead watering
that can splash spores around.
No comments:
Post a Comment