I do not know the PH level, but I have some azaleas that are doing very
well. I also fertilized the area with an acid heavy fertilizer designed for
acid loving plants.
The situation looked even worse this morning. I think I am too late no
matter what the problem is. :-(
"Stephen M. Henning" wrote in message
news
"wayne crimi" wrote:
I bought a rhododendron this spring and planted it in my garden. For
several months it seemed to be doing very well. Recently, I began to
notice
that some of the leaves on certain branches were developing brown areas.
Others were wilting. Slowly, the entire branch would just sort of dry
out
and die. However, other parts of the plant continued to sprout new
leaves
and grow. This process seems to have picked up some steam in the last 2
weeks. More sections are looking unhealthy. I fear it is going to slowly
die. Does anyone have any idea what the problem might be. I water
regularly and fertilized it in the spring with an appropriate
fertilizer. I
do believe it may be getting a bit too much sun, but other plants in the
neighborhood with similar sun are doing fine. (I am in NY)
First, do you know your soil pH. The most important factor in achieving
vigorous growth is an acid soil mixture high in organic content.
Rhododendron and azaleas need an acid soil with a pH of 5.0 to 6.0, well
mulched with organic material. Rhododendron thrive in a moist,
well-drained, humus-filled soil, enriched with peat moss or leaf mold.
Prepare the soil by thoroughly mixing equal parts of loam, coarse sand
and ground oak leaves or redwood before planting.
If the soil is too alkaline, acidity may be increased by adding flowers
of sulfur (powdered sulfur) or iron sulfate. I add 1 tablespoon of
sulfur powder around the base of any plant showing signs of chlorosis.
Do not use aluminum sulfate. Aluminum can build up in the soil to toxic
levels eventually. One very common source of chlorosis is when lime
leaches out of concrete, such as from a foundation or walkway, making
the nearby soil more alkaline. This problem decreases each year as the
concrete ages. An annual application of sulfur can compensate for this
problem.
Sphagnum peat or peat moss is a super soil amendment. Researchers claim
that plants planted in mixes containing sphagnum peat will resist
disease better. The sphagnum peat in the soil does regulate the
availability of water so the roots are not too wet, but also the
sphagnum is said to provide protection against disease.
The following are some pathologies that could cause your problem:
A) If a leaf has brown areas with white spots , it probably has a local
fungal infection of Pestalotia leaf spot . This is seldom controlled
with fungicides and is best mitigated by good sanitation and avoiding
excessive moisture.
B) Phytophthora causes the central vein of a leaf to turn brown and the
discoloration extends to the petiole on tender new growth. The
infections spreads outward from the midrib tissue and the leaf wilts.
Infections are more severe on azaleas. Some varieties of rhododendron
are vulnerable (Chionoides, Catawbiense Album, Nova Zembla) and some are
resistant (Roseum Elegans, Scintillation, PJM). Control of the disease
is difficult. Since the infection goes from the roots to the tips, when
you see the symptoms it is too late. To prevent it, use a raised bed
with lots of sphagnum peat moss. Prevention with fungicides and careful
control of exposure to high humidity may be practical.
C) Botryosphaeria causes leaves to turn dull green and then brown and
roll and droop . Cankers form on branches which may girdle the branch.
Sanitation and applying a fungicide after pruning my provide some
control.
D) Phomopsis symptoms vary from leaf spots to chlorosis and then
browning of leaves which then wilt. Browning streaks extend down the
stem to a wound. Fungicides should control an outbreak. Sanitation and
applying a fungicide after pruning may provide control.
E) Your description sounds most like borers. Ends of branches die when
rhododendron or azalea borer larvae tunnel in a stem. This affects the
portions of the plant away from the roots from where the borer larvae is
in the stem. Borers have done their damage when you see the wilting and
usually it is best to cut off the affected region. The requires removing
the damaged branch from the hole where the eggs were laid at the base of
the dying branch to remove any larvae before they become adults and
infect more plants. The parts that are cut off should be destroyed to
kill the larvae that are in them. Borers are prevented by following a
spray schedule (timing is very critical) for borers with chlorpyrifos or
lindane. Your county agent can help you with this information.
F) Plants wilt and die slowly when their roots become blocked. There are
two causes of this:
1) Root strangulation . This is best prevented by proper root pruning
when planting . If the plant is not too far gone, it might be rescued by
digging and removing the soil. Then cutting any circling roots that may
be strangling other roots. The roots need to be opened up. On larger
plants, some of the top must be removed to compensate for the weak state
of the roots. Any time the roots are exposed, they must be kept
moistened. Roots that dry out will die.
2) Phytophthora crown rot or wilt. This root rot is the major killer of
rhododendron and azaleas. It develops when roots are growing in wet
conditions. Plants infected with crown rot caused by the fungi
Phytophthora have roots which become clogged with brown fungi
internally. The roots get blocked and the plant wilts and dies. There is
not much of any cure for crown rot. Some varieties of rhododendron are
vulnerable (Chionoides, Catawbiense Album, Nova Zembla) and some are
resistant (Roseum Elegans, Scintillation, PJM). Sphagnum moss and bark
dust combined with good drainage seem to prevent crown rot, but do not
cure it.
--
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